bN

blueman

10/03/2010 8:53 AM

How tight to clamp glue-ups?

I've seen completely opposite opinions.
On the one hand I have seen "scientific" perspectives saying that even
a dense set of the best clamps can barely supply the "optimal" clamping
pressure.

On the other hand, I see the woodworking shows warning about not
clamping too tight so as to prevent glue squeezout and starving the
joint of glue.

So who is right the "scientists" or the "practitioners" or both?



This topic has 53 replies

FH

Father Haskell

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 2:57 PM

On Mar 10, 12:48=A0pm, "SonomaProducts.com" <[email protected]> wrote:
>
> If you are edge gluing panels, you should envision a 90 degree V
> extending from the location of the clamp at the edge, 45 degrees on
> either side of centerline of the clamp bar. The V's of the clamps
> should overlap at the glue joint, so wider boards in the panel require
> fewer clamps becaus ethe V covers more area as it extends away from
> the face. I actually have some outer cauls I have been using lately
> that essentially widen the panels that give me the side benefit of
> needing less clamps sometimes.

For the same reason, 2x4s or even 4x4s make better cauls
for general glueups than thin scrap, because they widen the
Vs at the glueline.

Even pressure is better than crushing pressure applied
at few points. The glue is stronger than needed in most
cases, but the finished joint will look neater.

kk

in reply to blueman on 10/03/2010 8:53 AM

14/03/2010 7:09 PM

On Sat, 13 Mar 2010 21:39:07 -0600, dpb <[email protected]> wrote:

>[email protected] wrote:
>...
>
>> Thinking about panel gluing here - seemingly the hardest for me. Does the
>> "cross linking" of the glue depend on pressure - a non-Newtonian fluid sort of
>> thing? Since the pressure forces the glue into the pores a high clamping
>> force is better (up to failure, of course). Excessive force can also warp the
>> material during the clamping time. To avoid this warping, and assuming
>> perfectly fitting components (yeah, right), the best strategy, might be to
>> clamp the hell out of it to force a thin glue line and into the pores, then
>> back off so the chance of warp is minimized? Will this release of pressure
>> cause a weaken glue joint? How long should the clamps remain on? I've always
>> tried to leave them on for 24 hours, but perhaps this isn't the best idea.
>
>A) For PVA, etc., I don't think the pressure is affecting the glue
>itself but is more the increase into the pores and the effect of less
>glue itself to be the weak point if you will...
>
>B) I don't think you want to clamp so strongly as to actually cause
>warping of the components to begin with. Again, the actual strength
>under relatively moderate pressures is generally all you'll really ever
>need.

It doesn't take a huge pressure to warp wood, given time.

>C) Clamp time is important -- it's dependent on the glue and the
>temperature/humidity so can't say unequivocally. In hot weather, I
>routinely continue working glue ups after a few hours; cooler weather
>wouldn't risk it. Overnight is generally pretty conservative unless
>really pushing the limits on temperatures (low).

I read that backwards, at first (continued working glue ups = were still
futzing with joints).

>
>> Well, there is a third issue. I'm certainly not a great woodworker and "well
>> fitting joints" are a relative thing - what is the best strategy for the home
>> woodworker?
>...
>
>Practice... :)

That's certainly my intention. ;-) I've always been interested in
woodworking. I now have the money, if not time, to play like I always wanted.
I retired once, but figure I'll try it permanently in another few years. I
want to be ready. ;-)

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 9:04 AM

I agree that PVA glues will develop a strong hold and rubbing in a
fit, like with corner blocks is totally valid. Hovere, if you are
talking edge gluing a panel, I have sse the studies regarding how much
clamp pressure and the outcomes are too little is less effective than
enough and too much is hard to achieve. I really don't think Franklin
(titebond) and others would clearly state clamping pressure is need
for optimal strength if it wasn't proven science. Although they could
be in some conspiracy with Bessy to make us all buy expensive but
useless clamps.

On Mar 11, 12:49=A0am, Chasgroh <[email protected]> wrote:
> >Marycanehoneycutt.comOn Wed, 10 Mar 2010 21:10:12 +0000 (UTC), Larry Bla=
nchard <[email protected]> wrote:
> >On Wed, 10 Mar 2010 08:53:31 -0500, blueman wrote:
>
> >> I've seen completely opposite opinions. On the one hand I have seen
> >> "scientific" perspectives saying that even a dense set of the best
> >> clamps can barely supply the "optimal" clamping pressure.
>
> >> On the other hand, I see the woodworking shows warning about not
> >> clamping too tight so as to prevent glue squeezout and starving the
> >> joint of glue.
>
> >> So who is right the "scientists" or the "practitioners" or both?
>
> >If you have tight fitting joints, hardly any pressure is needed. =A0If n=
ot,
> >no pressure is enough :-).
>
> >I've seen antique furniture with "rubbed" joint corner blocks that have
> >lasted and lasted and ...
>
> ...I use "rub blocks" frequently and have had opportunity to demo same
> for whatever reason...damn, they are VERY strong.
>
> cg
>
>
>
>
>
> >And don't overdo the glue. =A0A thin even coat on each piece, thin enoug=
h
> >that you can see the grain through the wet glue, is the best. =A0But I'v=
e
> >often gotten away with only coating one piece.- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 2:43 PM


"Chris Friesen" <[email protected]> wrote in message
news:[email protected]...
> On 03/10/2010 09:57 AM, Leon wrote:
>
>> Clamps sole purpose are to hold the pieces in alignment until the glue
>> cures.
>
> I disagree. Tests have shown that PVA glue joints are stronger when
> clamped tightly than when just "held in alignment". Whether that added
> strength is actually necessary is a different question.
>
>> You will never starve a joint of glue by clamping too tightly.
>
> Agreed.
>
> Chris
>

Well you are certainly welcome to disagree but I have on many many occasions
not used clamps on glue ups and the joints have never failed.
Including the panel glue up that was clamped, but not to my melamine TS
extension table. Squeeze out glued the panel to the laminate and the
laminate broke after jerking the panel up to free it from the TS.
Squeezing glue does not add to its strength.

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 10:15 AM

It has worked well for me... many hundreds of times, 24 times last
week.

On Mar 10, 10:06=A0am, -MIKE- <[email protected]> wrote:
> On 3/10/10 11:48 AM, SonomaProducts.com wrote:
>
> > If you are edge gluing panels, you should envision a 90 degree V
> > extending from the location of the clamp at the edge, 45 degrees on
> > either side of centerline of the clamp bar. The V's of the clamps
> > should overlap at the glue joint, so wider boards in the panel require
> > fewer clamps becaus ethe V covers more area as it extends away from
> > the face.
>
> Excellent description and practice.
>
> --
>
> =A0 -MIKE-
>
> =A0 "Playing is not something I do at night, it's my function in life"
> =A0 =A0 =A0--Elvin Jones =A0(1927-2004)
> =A0 --
> =A0http://mikedrums.com
> =A0 [email protected]
> =A0 ---remove "DOT" ^^^^ to reply

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 4:55 PM


"SonomaProducts.com" <[email protected]> wrote in message
news:c11a973b-e9b5-4792-834b-e9c1e0f466f4@t17g2000prg.googlegroups.com...
Unsolicited end-grain gluing info.

End-grain to any other grain, face, edge, end does not have any of the
same great qualities of a typical glue joint. The fibers being
perpendicular to the joint just don't allow for any long chain
attachment. One technique is to "size" the joint (not sure if that is
the right spelling for "size", I am speaking about the same concept as
used with wallpaper). Anyway, add glue to the end grain and then let
it mostly dry before putting the joint together. Then glue it again so
the joint is gluing the glue on the end grain to the other piece.
Haven't seen any science on this but have seen it recomended many
times. Could be old wives tail.


That is exactly what I do. Coat the end grain and let it soak in and then
reapply additional. Now if I am using pocket hole screws on the joint I
simply apply one coat to the endgrain. Kreg claims glue is not necessary
but IMHO it will not hurt.

LH

"Lew Hodgett"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 12:13 PM


"blueman" wrote:

> I've seen completely opposite opinions.
> On the one hand I have seen "scientific" perspectives saying that
> even
> a dense set of the best clamps can barely supply the "optimal"
> clamping
> pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?

--------------------------------------------
Depends.

If you are using typical wood working glues like TiteBond II, then
high clamping pressures are suggested by the manufacturer.

OTOH, if you are using quality epoxy, then only a minimum amount of
clamping pressure is required to hold pieces in place while epoxy
cures.

Different horses for different courses.

Lew


LH

"Lew Hodgett"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 9:02 PM


"blueman" wrote:

> Is higher clamping pressure bad for epoxy or just unnecessary?

High clamoing pressure starves the joint of epoxy needed for a good
joint.

> What about for the various polyurethane glues?

I chose not to comment on that garbage other than to say it is
overpriced and under peckered.

Lew



LH

"Lew Hodgett"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 5:58 PM

RE: Subject

When stuff stays stuck together where you want it after the clamps are
taken off, the clamps were tight enough in the first place.

Lew


LH

"Lew Hodgett"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 7:36 PM


--------------------------------
> Lew Hodgett wrote:
>> RE: Subject
>>
>> When stuff stays stuck together where you want it after the clamps
>> are taken off, the clamps were tight enough in the first place.
---------------------------------

"dpb" wrote:

> Again, right answer; different question...
-----------------------------------
No, right answer for the SUBJECT.

Different question requires different SUBJECT.

Lew


kk

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 8:55 AM

On Mar 10, 10:20=A0am, Chris Friesen <[email protected]> wrote:
> On 03/10/2010 09:57 AM, Leon wrote:
>
> > Clamps sole purpose are to hold the pieces in alignment until the glue
> > cures.
>
> I disagree. =A0Tests have shown that PVA glue joints are stronger when
> clamped tightly than when just "held in alignment". =A0Whether that added
> strength is actually necessary is a different question.

Is that because it takes pressure to minimize the glue (joint) width?
Just holding the boards in alignment may cause there to be too much
glue in the joint.

> > You will never starve a joint of glue by clamping too tightly.
>
> Agreed.

But you sure can warp the boards.

Cc

Chasgroh

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 12:49 AM

>Marycanehoneycutt.comOn Wed, 10 Mar 2010 21:10:12 +0000 (UTC), Larry Blanchard <[email protected]> wrote:

>On Wed, 10 Mar 2010 08:53:31 -0500, blueman wrote:
>
>> I've seen completely opposite opinions. On the one hand I have seen
>> "scientific" perspectives saying that even a dense set of the best
>> clamps can barely supply the "optimal" clamping pressure.
>>
>> On the other hand, I see the woodworking shows warning about not
>> clamping too tight so as to prevent glue squeezout and starving the
>> joint of glue.
>>
>> So who is right the "scientists" or the "practitioners" or both?
>
>If you have tight fitting joints, hardly any pressure is needed. If not,
>no pressure is enough :-).
>
>I've seen antique furniture with "rubbed" joint corner blocks that have
>lasted and lasted and ...

...I use "rub blocks" frequently and have had opportunity to demo same
for whatever reason...damn, they are VERY strong.

cg
>
>And don't overdo the glue. A thin even coat on each piece, thin enough
>that you can see the grain through the wet glue, is the best. But I've
>often gotten away with only coating one piece.

kk

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 1:51 PM

On Sat, 13 Mar 2010 09:29:47 -0600, dpb <[email protected]> wrote:

>[email protected] wrote:
>...
>
>> My point was that glue has a non-zero surface tension. To get the minimum
>> glue line width it takes some pressure, even if the surfaces are "perfectly"
>> flat. Is this the only pressure that matters, or is there something else
>> going on, like there is with pressure sensitive adhesives?
>...
>
>Yes, there is something else going on.
>
>In testing it's been shown that glue line thickness much thinner than
>are possible by manually distributing the glue and light pressure
>_does_, in fact, create a stonger bond (up to the point at which actual
>damage by compression of surfaces, etc., happens, of course).
>
>This is owing to to effects according to the analyses I've read --
>first, the glue itself crosslinks and is less material relying on it's
>on strength and the increased pressure also forces more into the wood
>pores where it adds strength as well.

Thanks, but of course a little understanding raises even more questions... ;-)

Thinking about panel gluing here - seemingly the hardest for me. Does the
"cross linking" of the glue depend on pressure - a non-Newtonian fluid sort of
thing? Since the pressure forces the glue into the pores a high clamping
force is better (up to failure, of course). Excessive force can also warp the
material during the clamping time. To avoid this warping, and assuming
perfectly fitting components (yeah, right), the best strategy, might be to
clamp the hell out of it to force a thin glue line and into the pores, then
back off so the chance of warp is minimized? Will this release of pressure
cause a weaken glue joint? How long should the clamps remain on? I've always
tried to leave them on for 24 hours, but perhaps this isn't the best idea.

>Again, granted, one can w/ well-prepared jointing surfaces that mate
>well get glue joints that are as strong as most applications need w/
>fairly minimal pressure but the research is clear that ultimate strength
>for identically-prepared and well-fitting joints is correlated w/
>increased clamping force/pressure.
>
>So, again, there are two questions here -- one is "how good is good
>enough for practical applications?" and the other is "what affects
>maximum glue joint strength achievable?"

Well, there is a third issue. I'm certainly not a great woodworker and "well
fitting joints" are a relative thing - what is the best strategy for the home
woodworker?

>Most of this research is, of course, oriented to applications for
>manufacturing facilities, not the casual (or even not so casual :) )
>woodworker w/ handcraft applications and clamping.

Indeed.

LJ

Larry Jaques

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 4:39 PM

On Wed, 10 Mar 2010 08:17:24 -0600, the infamous Swingman
<[email protected]> scrawled the following:

>On 3/10/2010 7:53 AM, blueman wrote:
>> I've seen completely opposite opinions.
>> On the one hand I have seen "scientific" perspectives saying that even
>> a dense set of the best clamps can barely supply the "optimal" clamping
>> pressure.
>>
>> On the other hand, I see the woodworking shows warning about not
>> clamping too tight so as to prevent glue squeezout and starving the
>> joint of glue.
>>
>> So who is right the "scientists" or the "practitioners" or both?
>
>The proof is in the pudding ...

You clamp pudding? Um, are we talkin' shaky puddin' here, Swingy?
I clamp onto that when it's around, too. (Go, Gator!)

--
There is no such thing as limits to growth, because there are no limits
to the human capacity for intelligence, imagination, and wonder.
-- Ronald Reagan

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 9:35 AM

Waaaa?

No, you need to clamp.

On Mar 10, 7:57=A0am, "Leon" <[email protected]> wrote:
> "blueman" <[email protected]> wrote in message
>
> news:[email protected]...
>
> > I've seen completely opposite opinions.
> > On the one hand I have seen "scientific" perspectives saying that even
> > a dense set of the best clamps can barely supply the "optimal" clamping
> > pressure.
>
> > On the other hand, I see the woodworking shows warning about not
> > clamping too tight so as to prevent glue squeezout and starving the
> > joint of glue.
>
> > So who is right the "scientists" or the "practitioners" or both?
>
> Things to consider. =A0The best joint contains 2 mating surfaces that are
> perfectly flat.
>
> Clamps sole purpose are to hold the pieces in alignment until the glue
> cures.
>
> Clamps are often used to squeeze an ill fitting joint into submission. =
=A0See
> above comment about the best joints.
>
> You can use masking tape to clamp a properly fitting joint.
>
> You will never starve a joint of glue by clamping too tightly. =A0Glue
> starvation is a condition that is caused by not applying glue properly in
> the first place. =A0Running a bead of glue down the edge or surface of a
> board and not spreading the glue over the entire surface is the first ste=
p
> to glue starvation. =A0A thin glue line is the best. =A0Tightly clamping =
an ill
> fitting joint to close the gap will aid in a better bond at the joint, it
> creates a thinner glue line, unfortunately an ill fitting joint may appea=
r
> to fail as the wood splits "next to" the actual glue line.

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 11:53 AM

Ahh yes, that was the article I was thinking of. I forgot about the
pressure over area calculation so my explaination was not complete.

On Mar 10, 10:32=A0am, Swingman <[email protected]> wrote:
> On 3/10/2010 12:06 PM, -MIKE- wrote:
>
> > On 3/10/10 11:48 AM, SonomaProducts.com wrote:
> >> If you are edge gluing panels, you should envision a 90 degree V
> >> extending from the location of the clamp at the edge, 45 degrees on
> >> either side of centerline of the clamp bar. The V's of the clamps
> >> should overlap at the glue joint, so wider boards in the panel require
> >> fewer clamps becaus ethe V covers more area as it extends away from
> >> the face.
>
> > Excellent description and practice.
>
> Belong to FWW online?
>
> http://www.finewoodworking.com/fwnpdf/011194036.pdf
>
> Page 40 ... worth the 14 day trial if you don't belong.
>
> --www.e-woodshop.net
> Last update: 10/22/08
> KarlC@ (the obvious)

LJ

Larry Jaques

in reply to blueman on 10/03/2010 8:53 AM

14/03/2010 7:48 PM

On Sat, 13 Mar 2010 21:44:53 -0600, the infamous dpb <[email protected]>
scrawled the following:

>Leon wrote:
>> "dpb" <[email protected]> wrote in message
>> news:[email protected]...
>>> Leon wrote:
>>> ...
>>>
>>>> And for the last 30 years I have verified by my own practice that the
>>>> joint is fine if properly set up to start with. Clamps are not
>>>> necessary. Try this, put some glue on a "flat" scrap, and "lay" another
>>>> flat piece of scrap on top, let set a few hours, see if you can break
>>>> apart with out the wood actually failing.
>>> Again, that's the right answer to a different question...
>>>
>>> --
>>
>> Actually I don't recall "you" asking a question. Did I miss your question?
>
>No, but there was lots of response to the OP's that I think wasn't quite
>right...addressing the difference between ultimate and "adequate"
>strength and effect of clamping pressure thereon.
>
>I'm not disagreeing it's possible to get "adequate for most
>circumstances" glue strength w/ moderate to even minimal clamping force
>but otoh there is a relationship between clamping force and ultimate
>strength obtainable that seems worthy of being recognized...

Isn't glue a pass/fail kind of situ? You either do it right and it
survives punishment or you get it wrong and it fails catastrophically.
Adequate = ultimate in this instance, wot?


--
No matter how cynical you are, it is impossible to keep up.
--Lily Tomlin

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 8:41 AM

Ahhh! My comments are backed up by Franklin!


Sk

Swingman

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 8:17 AM

On 3/10/2010 7:53 AM, blueman wrote:
> I've seen completely opposite opinions.
> On the one hand I have seen "scientific" perspectives saying that even
> a dense set of the best clamps can barely supply the "optimal" clamping
> pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?

The proof is in the pudding ...

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 4:46 PM


"dpb" <[email protected]> wrote in message
news:[email protected]...
> Larry Blanchard wrote:
>> On Thu, 11 Mar 2010 10:26:01 -0600, jev wrote:
>>
>>> The actual required clamp pressure for any bond involving a wood glue is
>>> a combination of the small amount of pressure required to squeeze the
>>> glue into a thin, consistent layer, and the pressure necessary the
>>> compensate for any distortion or lack of fit in the wood stock being
>>> used. That means when the surfaces of the pieces being joined are true,
>>> and there is no gap between the pieces when they are dry fit, very
>>> little pressure is required.
>>
>> That ought to settle the issue once and for all, but we all know it won't
>> :-).
>
> Of course, since you quoted _very_ selectively... :(
>
> The actual quoted message goes on to say
>
>> ... because the bond strength produced in a joint is the result
>> of the entanglement of the glue particles which have been drawn into
>> the pores and anchored to the wood on the two sides of the joint,
>> there is rarely any concern for applying so much pressure that the
>> glue is all squeezed out. In fact, the bond strength achieved increases
>> as the bondline or layer
>> of glue becomes thinner. ...
>
> That last sentence is the key to the argument; that while perhaps an
> adequately strong joint is achieved w/ minimal pressure (given the caveats
> above) if one wants or needs the full strength achievable higher clamping
> pressures will be required.

Ahh but you leave out the key comments. The thinner the glue layer the
better the stronger the bond. The comment was made and as I have pointed
out, that extra clamping pressure is only needed if the surfaaces do not
touch evenly along the joint line. If you have flat mating surfaces,
squeezing the glue tighter is not going to strengthen the glue.




Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 8:46 AM


"Larry Blanchard" <[email protected]> wrote in message
news:[email protected]...

>
> If you have tight fitting joints, hardly any pressure is needed. If not,
> no pressure is enough :-).
>
> I've seen antique furniture with "rubbed" joint corner blocks that have
> lasted and lasted and ...
>
> And don't overdo the glue. A thin even coat on each piece, thin enough
> that you can see the grain through the wet glue, is the best. But I've
> often gotten away with only coating one piece.


Actually I can not remember the last time I actually put glue on both sides
of the joint, my practice is one side only. Except when end grain is being
glued.

bb

"basilisk"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 8:12 AM


"blueman" <[email protected]> wrote in message
news:[email protected]...
> I've seen completely opposite opinions.
> On the one hand I have seen "scientific" perspectives saying that even
> a dense set of the best clamps can barely supply the "optimal" clamping
> pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?
>
>
If I am not mistaken, titebond recommends 100 to 150 psi,
this makes good tight joints that won't creep, with a lot of clamps this is
not too hard to get close to on edge gluing, but for laminating larger items
it would be almost impossible without spending a lot on equipment.

Get your fitting as close as possible and apply the most
amount of pressure you can, without damaging your work
or clamps, works for me.

basilisk

dd

"dadiOH"

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 8:27 AM

blueman wrote:

> Yeah - I actually read that article once upon a time but then last
> night I was watching the weekly online version of New Yankee Workshop
> classics and Norm was talking about not clamping too tight to avoid
> squeezout... so I just wanted to get some additional perspective on
> these seemingly conflicting viewpoints...


I *like* squeeze out. A little bit, proves I used enough glue.


--

dadiOH
____________________________

dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico


Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 8:17 AM


<[email protected]> wrote in message
news:[email protected]...
> On Fri, 12 Mar 2010 16:52:37 -0600, "Leon" <[email protected]> wrote:
>
>>
>><[email protected]> wrote in message
>>news:761338b6-0373-447a-ae5b-90d28bc59fc7@v20g2000yqv.googlegroups.com...
>>On Mar 10, 10:20 am, Chris Friesen <[email protected]> wrote:
>>> On 03/10/2010 09:57 AM, Leon wrote:
>>>
>>> > Clamps sole purpose are to hold the pieces in alignment until the glue
>>> > cures.
>>>
>>> I disagree. Tests have shown that PVA glue joints are stronger when
>>> clamped tightly than when just "held in alignment". Whether that added
>>> strength is actually necessary is a different question.
>>
>>>Is that because it takes pressure to minimize the glue (joint) width?
>>
>>Yes especially when the joint is visible before the glue is applied. If
>>you
>>have an ill fitting joint more pressure is required to close the joint.
>>
>>
>>>Just holding the boards in alignment may cause there to be too much
>>>glue in the joint.
>>
>>Just holding the joint together with out any pressure can be a perfecectly
>>strong joint if the glue is applied properly and not in excess. Too much
>>glue may in fact keep the joint from actually closing properly unless
>>clamped tightly enough to squeese the excess glue out. Ironically glue
>>squeeze out is an indicator the the joint is probably not going to be
>>starved of glue but it is also an indicator that more glue was used than
>>necessary.
>>
> My point was that glue has a non-zero surface tension. To get the minimum
> glue line width it takes some pressure, even if the surfaces are
> "perfectly"
> flat. Is this the only pressure that matters, or is there something else
> going on, like there is with pressure sensitive adhesives?

Yes some pressure is required if you apply too much glue so that you can get
the minimum thin layer of glue. Done properly the pressure that "tape"
exerts is adequate. With a normal PVA glue extra pressure on two properly
prepaired mating surfaces only insures that the union does not slip out of
alignment, maybe. With too much glue clamping pressure can be troublesome
with maintaining alignment, the parts want to shift.
If there are glues that work better under pressure I have not aware of them.
That is not to say that added pressure with PVA glues is a bad thing, added
pressure can close an ill mated joint where the two surfaces so not make
contact on the entire mating surfaces. BUT as we have both pointed out
this can also make the glued up panel warped or bowed if the clamping force
was considerable to bring both mating surfaces together.
Basically, as you are asking, you only need enough pressure to insure a
thing layer of glue. You can help insure a thin layer of glue by simply
applying a complete thin coat of glue to one surface. Less glue = less
clamping pressure.





CF

Chris Friesen

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 10:20 AM

On 03/10/2010 09:57 AM, Leon wrote:

> Clamps sole purpose are to hold the pieces in alignment until the glue
> cures.

I disagree. Tests have shown that PVA glue joints are stronger when
clamped tightly than when just "held in alignment". Whether that added
strength is actually necessary is a different question.

> You will never starve a joint of glue by clamping too tightly.

Agreed.

Chris

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 11:00 AM

Unsolicited end-grain gluing info.

End-grain to any other grain, face, edge, end does not have any of the
same great qualities of a typical glue joint. The fibers being
perpendicular to the joint just don't allow for any long chain
attachment. One technique is to "size" the joint (not sure if that is
the right spelling for "size", I am speaking about the same concept as
used with wallpaper). Anyway, add glue to the end grain and then let
it mostly dry before putting the joint together. Then glue it again so
the joint is gluing the glue on the end grain to the other piece.
Haven't seen any science on this but have seen it recomended many
times. Could be old wives tail.

On Mar 12, 6:46=A0am, "Leon" <[email protected]> wrote:
> "Larry Blanchard" <[email protected]> wrote in message
>
> news:[email protected]...
>
>
>
> > If you have tight fitting joints, hardly any pressure is needed. =A0If =
not,
> > no pressure is enough :-).
>
> > I've seen antique furniture with "rubbed" joint corner blocks that have
> > lasted and lasted and ...
>
> > And don't overdo the glue. =A0A thin even coat on each piece, thin enou=
gh
> > that you can see the grain through the wet glue, is the best. =A0But I'=
ve
> > often gotten away with only coating one piece.
>
> Actually I can not remember the last time I actually put glue on both sid=
es
> of the joint, my practice is one side only. =A0Except when end grain is b=
eing
> glued.

Sb

"SonomaProducts.com"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 9:48 AM

There is lots of practical info published on this for PVA glues
(Titebond wood glue, etc.). FWW magazine had a study a while back. a
few hundred lbs clamping force is what is needed. The most important
things the study show is that various types of clamps have widely
different capacities to generate clamping force. The modern parallel
clamps can get to a thousand + pounds. Thin bar clamps can struggle to
get to 150 lbs. Pipe clamps IIRC can also create quite some force.
Strangely they report the pistol grip clamps also generate huge
amounts of force but I just can't believe it. I just use them for
positioning and lite work.

So use good clamps and there is no need to overtighten. Clamp until
you see squeeze and give it another little twist just to be sure.
Trust me, masking tape ain't gonna do it with PVA glue.

If you are edge gluing panels, you should envision a 90 degree V
extending from the location of the clamp at the edge, 45 degrees on
either side of centerline of the clamp bar. The V's of the clamps
should overlap at the glue joint, so wider boards in the panel require
fewer clamps becaus ethe V covers more area as it extends away from
the face. I actually have some outer cauls I have been using lately
that essentially widen the panels that give me the side benefit of
needing less clamps sometimes.

On Mar 10, 5:53=A0am, blueman <[email protected]> wrote:
> I've seen completely opposite opinions.
> On the one hand I have seen "scientific" perspectives saying that even
> a dense set of the best clamps can barely supply the "optimal" clamping
> pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?

Sk

Swingman

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 12:32 PM

On 3/10/2010 12:06 PM, -MIKE- wrote:
> On 3/10/10 11:48 AM, SonomaProducts.com wrote:
>> If you are edge gluing panels, you should envision a 90 degree V
>> extending from the location of the clamp at the edge, 45 degrees on
>> either side of centerline of the clamp bar. The V's of the clamps
>> should overlap at the glue joint, so wider boards in the panel require
>> fewer clamps becaus ethe V covers more area as it extends away from
>> the face.
>
>
> Excellent description and practice.

Belong to FWW online?

http://www.finewoodworking.com/fwnpdf/011194036.pdf

Page 40 ... worth the 14 day trial if you don't belong.

--
www.e-woodshop.net
Last update: 10/22/08
KarlC@ (the obvious)

LJ

Larry Jaques

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 6:48 AM

On Wed, 10 Mar 2010 21:10:12 +0000 (UTC), the infamous Larry Blanchard
<[email protected]> scrawled the following:

>On Wed, 10 Mar 2010 08:53:31 -0500, blueman wrote:
>
>> I've seen completely opposite opinions. On the one hand I have seen
>> "scientific" perspectives saying that even a dense set of the best
>> clamps can barely supply the "optimal" clamping pressure.
>>
>> On the other hand, I see the woodworking shows warning about not
>> clamping too tight so as to prevent glue squeezout and starving the
>> joint of glue.
>>
>> So who is right the "scientists" or the "practitioners" or both?
>
>If you have tight fitting joints, hardly any pressure is needed. If not,
>no pressure is enough :-).

Ayup.
http://ifonlyyouwood.blogspot.com/2009/08/clamping-for-pva-glue.html


>I've seen antique furniture with "rubbed" joint corner blocks that have
>lasted and lasted and ...

Is this simply applying glue and moving the joint around to ensure
even application?


>And don't overdo the glue. A thin even coat on each piece, thin enough
>that you can see the grain through the wet glue, is the best. But I've
>often gotten away with only coating one piece.

That's good. I go a bit thicker than that on softwoods as they absorb
considerably more of it.

--
There is no such thing as limits to growth, because there are no limits
to the human capacity for intelligence, imagination, and wonder.
-- Ronald Reagan

Mm

-MIKE-

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 12:06 PM

On 3/10/10 11:48 AM, SonomaProducts.com wrote:
> If you are edge gluing panels, you should envision a 90 degree V
> extending from the location of the clamp at the edge, 45 degrees on
> either side of centerline of the clamp bar. The V's of the clamps
> should overlap at the glue joint, so wider boards in the panel require
> fewer clamps becaus ethe V covers more area as it extends away from
> the face.


Excellent description and practice.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply

LB

Larry Blanchard

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 9:10 PM

On Wed, 10 Mar 2010 08:53:31 -0500, blueman wrote:

> I've seen completely opposite opinions. On the one hand I have seen
> "scientific" perspectives saying that even a dense set of the best
> clamps can barely supply the "optimal" clamping pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?

If you have tight fitting joints, hardly any pressure is needed. If not,
no pressure is enough :-).

I've seen antique furniture with "rubbed" joint corner blocks that have
lasted and lasted and ...

And don't overdo the glue. A thin even coat on each piece, thin enough
that you can see the grain through the wet glue, is the best. But I've
often gotten away with only coating one piece.

--
Intelligence is an experiment that failed - G. B. Shaw

LB

Larry Blanchard

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 5:44 PM

On Thu, 11 Mar 2010 06:48:55 -0800, Larry Jaques wrote:

>>I've seen antique furniture with "rubbed" joint corner blocks that have
>>lasted and lasted and ...
>
> Is this simply applying glue and moving the joint around to ensure even
> application?

More or less. I move the wood just 1/4" or so till I feel it start to
grab. Then press it into the desired location - no clamps needed.

--
Intelligence is an experiment that failed - G. B. Shaw

LB

Larry Blanchard

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 5:47 PM

On Wed, 10 Mar 2010 21:02:57 -0800, Lew Hodgett wrote:

>> What about for the various polyurethane glues?
>
> I chose not to comment on that garbage other than to say it is
> overpriced and under peckered.

Amen, brother!

--
Intelligence is an experiment that failed - G. B. Shaw

LB

Larry Blanchard

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 5:51 PM

On Thu, 11 Mar 2010 10:26:01 -0600, jev wrote:

> The actual required clamp pressure for any bond involving a wood glue is
> a combination of the small amount of pressure required to squeeze the
> glue into a thin, consistent layer, and the pressure necessary the
> compensate for any distortion or lack of fit in the wood stock being
> used. That means when the surfaces of the pieces being joined are true,
> and there is no gap between the pieces when they are dry fit, very
> little pressure is required.

That ought to settle the issue once and for all, but we all know it
won't :-).

Wonder what those high pressure advocates would say about yellow glue,
veneer, and a household iron?

--
Intelligence is an experiment that failed - G. B. Shaw

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 9:40 AM

Larry Blanchard wrote:
> On Thu, 11 Mar 2010 10:26:01 -0600, jev wrote:
>
>> The actual required clamp pressure for any bond involving a wood glue is
>> a combination of the small amount of pressure required to squeeze the
>> glue into a thin, consistent layer, and the pressure necessary the
>> compensate for any distortion or lack of fit in the wood stock being
>> used. That means when the surfaces of the pieces being joined are true,
>> and there is no gap between the pieces when they are dry fit, very
>> little pressure is required.
>
> That ought to settle the issue once and for all, but we all know it
> won't :-).

Of course, since you quoted _very_ selectively... :(

The actual quoted message goes on to say

> ... because the bond strength produced in a joint is the result
> of the entanglement of the glue particles which have been drawn into
> the pores and anchored to the wood on the two sides of the joint,
> there is rarely any concern for applying so much pressure that the
> glue is all squeezed out.
>
> In fact, the bond strength achieved increases as the bondline or layer
> of glue becomes thinner. ...

That last sentence is the key to the argument; that while perhaps an
adequately strong joint is achieved w/ minimal pressure (given the
caveats above) if one wants or needs the full strength achievable higher
clamping pressures will be required.

This is what has been unequivocally demonstrated in test after test
after test and can be found in US Forest Products research reports for
(afaik) virtually all single material glues and most others such a
resorcinol, etc.


> Wonder what those high pressure advocates would say about yellow glue,
> veneer, and a household iron?

Same thing...while not normally required for the application, a vacuum
press and cauling would yield a stronger bond.

Whether it's necessary or not for the application is a different
question than whether it does or doesn't have an effect.

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 7:22 PM

Leon wrote:
...

> Ahh but you leave out the key comments. The thinner the glue layer the
> better the stronger the bond. The comment was made and as I have pointed
> out, that extra clamping pressure is only needed if the surfaaces do not
> touch evenly along the joint line. If you have flat mating surfaces,
> squeezing the glue tighter is not going to strengthen the glue.
...

No, the effect of the extra gluing pressure contributes by helping in
creating the thinner bonding layer as well as inducing (as the above
alluded to as well) more integrated into the wood pores.

As noted above, these results have been verified over and over and over
w/ identically prepared samples taking out the variable of the quality
of the jointing surfaces, etc.

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 9:02 PM

Leon wrote:
...

> And for the last 30 years I have verified by my own practice that the joint
> is fine if properly set up to start with. Clamps are not necessary. Try
> this, put some glue on a "flat" scrap, and "lay" another flat piece of scrap
> on top, let set a few hours, see if you can break apart with out the wood
> actually failing.

Again, that's the right answer to a different question...

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 9:03 PM

Lew Hodgett wrote:
> RE: Subject
>
> When stuff stays stuck together where you want it after the clamps are
> taken off, the clamps were tight enough in the first place.
>
Again, right answer; different question...

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 9:29 AM

[email protected] wrote:
...

> My point was that glue has a non-zero surface tension. To get the minimum
> glue line width it takes some pressure, even if the surfaces are "perfectly"
> flat. Is this the only pressure that matters, or is there something else
> going on, like there is with pressure sensitive adhesives?
...

Yes, there is something else going on.

In testing it's been shown that glue line thickness much thinner than
are possible by manually distributing the glue and light pressure
_does_, in fact, create a stonger bond (up to the point at which actual
damage by compression of surfaces, etc., happens, of course).

This is owing to to effects according to the analyses I've read --
first, the glue itself crosslinks and is less material relying on it's
on strength and the increased pressure also forces more into the wood
pores where it adds strength as well.

Again, granted, one can w/ well-prepared jointing surfaces that mate
well get glue joints that are as strong as most applications need w/
fairly minimal pressure but the research is clear that ultimate strength
for identically-prepared and well-fitting joints is correlated w/
increased clamping force/pressure.

So, again, there are two questions here -- one is "how good is good
enough for practical applications?" and the other is "what affects
maximum glue joint strength achievable?"

Most of this research is, of course, oriented to applications for
manufacturing facilities, not the casual (or even not so casual :) )
woodworker w/ handcraft applications and clamping.

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 9:39 PM

[email protected] wrote:
...

> Thinking about panel gluing here - seemingly the hardest for me. Does the
> "cross linking" of the glue depend on pressure - a non-Newtonian fluid sort of
> thing? Since the pressure forces the glue into the pores a high clamping
> force is better (up to failure, of course). Excessive force can also warp the
> material during the clamping time. To avoid this warping, and assuming
> perfectly fitting components (yeah, right), the best strategy, might be to
> clamp the hell out of it to force a thin glue line and into the pores, then
> back off so the chance of warp is minimized? Will this release of pressure
> cause a weaken glue joint? How long should the clamps remain on? I've always
> tried to leave them on for 24 hours, but perhaps this isn't the best idea.

A) For PVA, etc., I don't think the pressure is affecting the glue
itself but is more the increase into the pores and the effect of less
glue itself to be the weak point if you will...

B) I don't think you want to clamp so strongly as to actually cause
warping of the components to begin with. Again, the actual strength
under relatively moderate pressures is generally all you'll really ever
need.

C) Clamp time is important -- it's dependent on the glue and the
temperature/humidity so can't say unequivocally. In hot weather, I
routinely continue working glue ups after a few hours; cooler weather
wouldn't risk it. Overnight is generally pretty conservative unless
really pushing the limits on temperatures (low).

...

> Well, there is a third issue. I'm certainly not a great woodworker and "well
> fitting joints" are a relative thing - what is the best strategy for the home
> woodworker?
...

Practice... :)

--

dn

dpb

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 9:44 PM

Leon wrote:
> "dpb" <[email protected]> wrote in message
> news:[email protected]...
>> Leon wrote:
>> ...
>>
>>> And for the last 30 years I have verified by my own practice that the
>>> joint is fine if properly set up to start with. Clamps are not
>>> necessary. Try this, put some glue on a "flat" scrap, and "lay" another
>>> flat piece of scrap on top, let set a few hours, see if you can break
>>> apart with out the wood actually failing.
>> Again, that's the right answer to a different question...
>>
>> --
>
> Actually I don't recall "you" asking a question. Did I miss your question?

No, but there was lots of response to the OP's that I think wasn't quite
right...addressing the difference between ultimate and "adequate"
strength and effect of clamping pressure thereon.

I'm not disagreeing it's possible to get "adequate for most
circumstances" glue strength w/ moderate to even minimal clamping force
but otoh there is a relationship between clamping force and ultimate
strength obtainable that seems worthy of being recognized...

--

LJ

Larry Jaques

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 6:03 AM

On Wed, 10 Mar 2010 09:35:11 -0800 (PST), the infamous
"SonomaProducts.com" <[email protected]> scrawled the following:

topposting repaired


>On Mar 10, 7:57 am, "Leon" <[email protected]> wrote:
>> "blueman" <[email protected]> wrote in message
>>
>> news:[email protected]...
>>
>> > I've seen completely opposite opinions.
>> > On the one hand I have seen "scientific" perspectives saying that even
>> > a dense set of the best clamps can barely supply the "optimal" clamping
>> > pressure.
>>
>> > On the other hand, I see the woodworking shows warning about not
>> > clamping too tight so as to prevent glue squeezout and starving the
>> > joint of glue.
>>
>> > So who is right the "scientists" or the "practitioners" or both?
>>
>> Things to consider.  The best joint contains 2 mating surfaces that are
>> perfectly flat.
>>
>> Clamps sole purpose are to hold the pieces in alignment until the glue
>> cures.
>>
>> Clamps are often used to squeeze an ill fitting joint into submission.  See
>> above comment about the best joints.
>>
>> You can use masking tape to clamp a properly fitting joint.
>
>Waaaa?
>
>No, you need to clamp.

I've used masking tape as a clamp to glue two pieces of pine together
and the joint was perfectly strong. Oak to MDF is the same: tape for
alignment and the weight of the project (reject countertop) for
clamping pressure. I agree that you need some pressure, and that's
especially true if the boards you have aren't perfectly flat, but all
of us tend to overclamp things. I believe that 100psi is optimum, and
out little HF bar clamps are capable of 1kpsi, so don't worry about
wimpy clamps not being enough.

If you disagree, grab a pair of your favorite clamps and your
household scale. Use boards (1" square if you're a purist or anal
engineering type ;) to protect the metal as you gingerly tighten them
on the scale. Note how softly you can twist before it tops out,
remembering how snugly you crank them suckahs down on a project.
Amazing, isn't it?

--
There is no such thing as limits to growth, because there are no limits
to the human capacity for intelligence, imagination, and wonder.
-- Ronald Reagan

jr

jev

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 10:26 AM

On Wed, 10 Mar 2010 09:57:54 -0600, "Leon" <[email protected]>
wrote:

>
>"blueman" <[email protected]> wrote in message
>news:[email protected]...
>> I've seen completely opposite opinions.
>> On the one hand I have seen "scientific" perspectives saying that even
>> a dense set of the best clamps can barely supply the "optimal" clamping
>> pressure.
>>
>> On the other hand, I see the woodworking shows warning about not
>> clamping too tight so as to prevent glue squeezout and starving the
>> joint of glue.
>>
>> So who is right the "scientists" or the "practitioners" or both?
>
>
>Things to consider. The best joint contains 2 mating surfaces that are
>perfectly flat.
>
>Clamps sole purpose are to hold the pieces in alignment until the glue
>cures.
>
>Clamps are often used to squeeze an ill fitting joint into submission. See
>above comment about the best joints.
>
>You can use masking tape to clamp a properly fitting joint.
>
>You will never starve a joint of glue by clamping too tightly. Glue
>starvation is a condition that is caused by not applying glue properly in
>the first place. Running a bead of glue down the edge or surface of a
>board and not spreading the glue over the entire surface is the first step
>to glue starvation. A thin glue line is the best. Tightly clamping an ill
>fitting joint to close the gap will aid in a better bond at the joint, it
>creates a thinner glue line, unfortunately an ill fitting joint may appear
>to fail as the wood splits "next to" the actual glue line.
>

I have lost the identity of the original poster of the text below but
a rep of Ttitebond addresses the 'pressure' issue .

Response from Frnklain/Titebond rep re:Calmping Pressure


After our discussion here, I wrote to technical support at Titebond
regarding our discussion of clamp pressure. I got a next day reply
from a very knowledgeable and helpful gentleman, Mr. Zimmerman. I'm
posting it here.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I am writing in response to your question about clamp pressure.
First, your calculation and understanding is correct. If you wanted
to produce 200 psi over an area 12" x 12", you would need 28,800
pounds of force. On the other hand, it is not clear whether you
often, or ever, fell short of the actual, required clamp pressure.

The actual required clamp pressure for any bond involving a wood glue
is a combination of the small amount of pressure required to squeeze
the glue into a thin, consistent layer, and the pressure necessary the
compensate for any distortion or lack of fit in the wood stock being
used. That means when the surfaces of the pieces being joined are
true, and there is no gap between the pieces when they are dry fit,
very little pressure is required. If, however, the same assembly is
being made using pieces which are bowed, twisted or ill-fitted, the
required pressure is much greater, and is largely the pressure
required to straighten the wood and pull it into position. Thus, the
actual required pressure for a bond also reflects the thickness, or
fight, of the wood involved, with much more pressure obviously
required to straighten a very thick piece of maple or oak than to
straighten a thinner piece of the same species.

In many applications, then, pressure, serves to compensate for some
lack of diligence in wood preparation. That being the case, good wood
preparation lessens the need for, or dependence on, pressure. In the
case of our literature, the high suggested pressures reflect the fact
that those individuals being addressed include those who, at least on
occasion, are trying to bond thick, poorly fitted pieces of wood, and
for those readers, the high, suggested values are, indeed, necessary.

Finally, because the bond strength produced in a joint is the result
of the entanglement of the glue particles which have been drawn into
the pores and anchored to the wood on the two sides of the joint,
there is rarely any concern for applying so much pressure that the
glue is all squeezed out.

In fact, the bond strength achieved increases as the bondline or layer
of glue becomes thinner. Given that fact, there are only two
situations in which high pressures may be counterproductive. First,
there is always a concern that the pores of wood at the bonding
surfaces not be crushed, and that is the reason that our listed
pressures are lower for the softer woods. The second situation deals
with bonds involving end grain or other open grain. There the concern
is that the open grain is prone to suck up a large amount of glue and,
if that thirst has not been quenched before clamping, that excessive
absorption of glue may result in a starved, and weak joint. Because
most bonds involve face or edge grain which is relatively straight,
that particular risk is rarely a concern.

I hope this response is helpful, and ask that you feel free to write
again or to call me at 1-800-###-#### if I can be of any further
assistance.

kk

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 7:56 PM

On Fri, 12 Mar 2010 16:52:37 -0600, "Leon" <[email protected]> wrote:

>
><[email protected]> wrote in message
>news:761338b6-0373-447a-ae5b-90d28bc59fc7@v20g2000yqv.googlegroups.com...
>On Mar 10, 10:20 am, Chris Friesen <[email protected]> wrote:
>> On 03/10/2010 09:57 AM, Leon wrote:
>>
>> > Clamps sole purpose are to hold the pieces in alignment until the glue
>> > cures.
>>
>> I disagree. Tests have shown that PVA glue joints are stronger when
>> clamped tightly than when just "held in alignment". Whether that added
>> strength is actually necessary is a different question.
>
>>Is that because it takes pressure to minimize the glue (joint) width?
>
>Yes especially when the joint is visible before the glue is applied. If you
>have an ill fitting joint more pressure is required to close the joint.
>
>
>>Just holding the boards in alignment may cause there to be too much
>>glue in the joint.
>
>Just holding the joint together with out any pressure can be a perfecectly
>strong joint if the glue is applied properly and not in excess. Too much
>glue may in fact keep the joint from actually closing properly unless
>clamped tightly enough to squeese the excess glue out. Ironically glue
>squeeze out is an indicator the the joint is probably not going to be
>starved of glue but it is also an indicator that more glue was used than
>necessary.
>
My point was that glue has a non-zero surface tension. To get the minimum
glue line width it takes some pressure, even if the surfaces are "perfectly"
flat. Is this the only pressure that matters, or is there something else
going on, like there is with pressure sensitive adhesives?

>
>> > You will never starve a joint of glue by clamping too tightly.
>>
>> Agreed.
>
>But you sure can warp the boards.
>
>Yup.
>

bN

blueman

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 10:55 PM

"Lew Hodgett" <[email protected]> writes:
> "blueman" wrote:
>
>> I've seen completely opposite opinions.
>> On the one hand I have seen "scientific" perspectives saying that
>> even
>> a dense set of the best clamps can barely supply the "optimal"
>> clamping
>> pressure.
>>
>> On the other hand, I see the woodworking shows warning about not
>> clamping too tight so as to prevent glue squeezout and starving the
>> joint of glue.
>>
>> So who is right the "scientists" or the "practitioners" or both?
>
> --------------------------------------------
> Depends.
>
> If you are using typical wood working glues like TiteBond II, then
> high clamping pressures are suggested by the manufacturer.
>
> OTOH, if you are using quality epoxy, then only a minimum amount of
> clamping pressure is required to hold pieces in place while epoxy
> cures.

Is higher clamping pressure bad for epoxy or just unnecessary?

What about for the various polyurethane glues?

bN

blueman

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 10:54 PM

Swingman <[email protected]> writes:

> On 3/10/2010 12:06 PM, -MIKE- wrote:
>> On 3/10/10 11:48 AM, SonomaProducts.com wrote:
>>> If you are edge gluing panels, you should envision a 90 degree V
>>> extending from the location of the clamp at the edge, 45 degrees on
>>> either side of centerline of the clamp bar. The V's of the clamps
>>> should overlap at the glue joint, so wider boards in the panel require
>>> fewer clamps becaus ethe V covers more area as it extends away from
>>> the face.
>>
>>
>> Excellent description and practice.
>
> Belong to FWW online?
>
> http://www.finewoodworking.com/fwnpdf/011194036.pdf
>
> Page 40 ... worth the 14 day trial if you don't belong.

Yeah - I actually read that article once upon a time but then last night
I was watching the weekly online version of New Yankee Workshop classics
and Norm was talking about not clamping too tight to avoid squeezout...
so I just wanted to get some additional perspective on these seemingly
conflicting viewpoints...

I guess I tend to believe the science, but on the other hand real life
doesn't always follow theory ;)

bN

blueman

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 10:52 PM

"SonomaProducts.com" <[email protected]> writes:

> There is lots of practical info published on this for PVA glues
> (Titebond wood glue, etc.). FWW magazine had a study a while back. a
> few hundred lbs clamping force is what is needed. The most important
> things the study show is that various types of clamps have widely
> different capacities to generate clamping force. The modern parallel
> clamps can get to a thousand + pounds. Thin bar clamps can struggle to
> get to 150 lbs. Pipe clamps IIRC can also create quite some force.
> Strangely they report the pistol grip clamps also generate huge
> amounts of force but I just can't believe it. I just use them for
> positioning and lite work.
>
> So use good clamps and there is no need to overtighten. Clamp until
> you see squeeze and give it another little twist just to be sure.
> Trust me, masking tape ain't gonna do it with PVA glue.
>
> If you are edge gluing panels, you should envision a 90 degree V
> extending from the location of the clamp at the edge, 45 degrees on
> either side of centerline of the clamp bar. The V's of the clamps
> should overlap at the glue joint, so wider boards in the panel require
> fewer clamps becaus ethe V covers more area as it extends away from
> the face. I actually have some outer cauls I have been using lately
> that essentially widen the panels that give me the side benefit of
> needing less clamps sometimes.
>

Thanks to you and others for the very helpful explanation...

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

13/03/2010 8:20 AM


"dpb" <[email protected]> wrote in message
news:[email protected]...
> Leon wrote:
> ...
>
>> And for the last 30 years I have verified by my own practice that the
>> joint is fine if properly set up to start with. Clamps are not
>> necessary. Try this, put some glue on a "flat" scrap, and "lay" another
>> flat piece of scrap on top, let set a few hours, see if you can break
>> apart with out the wood actually failing.
>
> Again, that's the right answer to a different question...
>
> --

Actually I don't recall "you" asking a question. Did I miss your question?

Pn

Phisherman

in reply to blueman on 10/03/2010 8:53 AM

11/03/2010 7:17 PM

On Wed, 10 Mar 2010 08:53:31 -0500, blueman <[email protected]> wrote:

>I've seen completely opposite opinions.
>On the one hand I have seen "scientific" perspectives saying that even
>a dense set of the best clamps can barely supply the "optimal" clamping
>pressure.
>
>On the other hand, I see the woodworking shows warning about not
>clamping too tight so as to prevent glue squeezout and starving the
>joint of glue.
>
>So who is right the "scientists" or the "practitioners" or both?
>
>


How the joint fits is of most importance with regard to strength. I
apply just enough glue so that just a small amount oozes out. My
clamps are "hand tight," but not "muscled tight." I dont believe a
joint is starved of glue, some is absorbed into the wood fibers. Apply
a thin coat of glue to both mating surfaces if using carpenter's
yellow glue.

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 7:42 PM


"dpb" <[email protected]> wrote in message
news:[email protected]...
> Leon wrote:
> ...
>
>> Ahh but you leave out the key comments. The thinner the glue layer the
>> better the stronger the bond. The comment was made and as I have
>> pointed out, that extra clamping pressure is only needed if the surfaaces
>> do not touch evenly along the joint line. If you have flat mating
>> surfaces, squeezing the glue tighter is not going to strengthen the glue.
> ...
>
> No, the effect of the extra gluing pressure contributes by helping in
> creating the thinner bonding layer as well as inducing (as the above
> alluded to as well) more integrated into the wood pores.

If you put the proper amount of glue on in the first place there is no need
to squeeze excess glue out. If you are working with flat mating surfaces
and don't use excess glue there is no need to clamp except to keep the
pieces properly aligned.

>
> As noted above, these results have been verified over and over and over w/
> identically prepared samples taking out the variable of the quality of the
> jointing surfaces, etc.

And for the last 30 years I have verified by my own practice that the joint
is fine if properly set up to start with. Clamps are not necessary. Try
this, put some glue on a "flat" scrap, and "lay" another flat piece of scrap
on top, let set a few hours, see if you can break apart with out the wood
actually failing.


Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 4:52 PM


<[email protected]> wrote in message
news:761338b6-0373-447a-ae5b-90d28bc59fc7@v20g2000yqv.googlegroups.com...
On Mar 10, 10:20 am, Chris Friesen <[email protected]> wrote:
> On 03/10/2010 09:57 AM, Leon wrote:
>
> > Clamps sole purpose are to hold the pieces in alignment until the glue
> > cures.
>
> I disagree. Tests have shown that PVA glue joints are stronger when
> clamped tightly than when just "held in alignment". Whether that added
> strength is actually necessary is a different question.

>Is that because it takes pressure to minimize the glue (joint) width?

Yes especially when the joint is visible before the glue is applied. If you
have an ill fitting joint more pressure is required to close the joint.


>Just holding the boards in alignment may cause there to be too much
>glue in the joint.

Just holding the joint together with out any pressure can be a perfecectly
strong joint if the glue is applied properly and not in excess. Too much
glue may in fact keep the joint from actually closing properly unless
clamped tightly enough to squeese the excess glue out. Ironically glue
squeeze out is an indicator the the joint is probably not going to be
starved of glue but it is also an indicator that more glue was used than
necessary.




> > You will never starve a joint of glue by clamping too tightly.
>
> Agreed.

But you sure can warp the boards.

Yup.

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

10/03/2010 9:57 AM


"blueman" <[email protected]> wrote in message
news:[email protected]...
> I've seen completely opposite opinions.
> On the one hand I have seen "scientific" perspectives saying that even
> a dense set of the best clamps can barely supply the "optimal" clamping
> pressure.
>
> On the other hand, I see the woodworking shows warning about not
> clamping too tight so as to prevent glue squeezout and starving the
> joint of glue.
>
> So who is right the "scientists" or the "practitioners" or both?


Things to consider. The best joint contains 2 mating surfaces that are
perfectly flat.

Clamps sole purpose are to hold the pieces in alignment until the glue
cures.

Clamps are often used to squeeze an ill fitting joint into submission. See
above comment about the best joints.

You can use masking tape to clamp a properly fitting joint.

You will never starve a joint of glue by clamping too tightly. Glue
starvation is a condition that is caused by not applying glue properly in
the first place. Running a bead of glue down the edge or surface of a
board and not spreading the glue over the entire surface is the first step
to glue starvation. A thin glue line is the best. Tightly clamping an ill
fitting joint to close the gap will aid in a better bond at the joint, it
creates a thinner glue line, unfortunately an ill fitting joint may appear
to fail as the wood splits "next to" the actual glue line.

Ll

"Leon"

in reply to blueman on 10/03/2010 8:53 AM

12/03/2010 8:44 AM


"dadiOH" <[email protected]> wrote in message
news:[email protected]...
> blueman wrote:
>
>> Yeah - I actually read that article once upon a time but then last
>> night I was watching the weekly online version of New Yankee Workshop
>> classics and Norm was talking about not clamping too tight to avoid
>> squeezout... so I just wanted to get some additional perspective on
>> these seemingly conflicting viewpoints...
>
>
> I *like* squeeze out. A little bit, proves I used enough glue.


Precicely, and for those that like the "glue starvation" cautionary
statement, it helps to indicate that there should be no glue starvation.


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