I have built a mirror frame from cherry. I am planning to use two pieces
24" of aluminum J-channel with one piece reversed, as a hanger at the top -
sort of a french cleat arrangement. I've recessed one of the pieces into the
frame. I was thinking of embedding it in West System epoxy to fasten it.
Does anyone happen to know if West System does OK with aluminum without
buying that 'etching' kit' from West ? Seems like a shame to spend that
much money on that kit for a 1x24 hanger. I suppose I can just screw it
down but I've only got about 3/8 depth there, after routing it out for the
recess.
Thanks
jim
Jim, bet you won't get anyone to touch this one. No one will want to
be responsible if your mirror DOESN'T hold and they have given you bad
advice. I cannot imagine you telling your SO that you explicity
followed the instructions given to you by someone in Chatanooga for
hanging your mirror.
If there is any doubt, by the etching kit. It does two things: cleans
the metal to remove all traces of hand oil, manufacturing oils, dust,
dirt, etc. It also literally etches the metal to provide a grippable
surface for the adhesive.
I know when we put in a shower/tub enclosure and the aluminum is not
properly wiped down we even have problems with out gooey sealants
sticking.
Why gamble with your project? Maybe you can recess the hanger about
1/8", and then adhere your channel. I think I would feel better about
that then just glueing it on. Of course, I would etch, too. Maybe
you could find the etching material at one of the metal shops in your
area if you feel West's is too high.
Robert
On 5-Dec-2005, "Jim Bailey" <[email protected]> wrote:
> I suppose I can just screw it
> down but I've only got about 3/8 depth there, after routing it out for the
> recess.
When finished, is the aluminum going to be flush with the wood surface?
When you say it's a J channel - is the J part curved or squared?
The reason I'm asking is that if the top of the J channel is sitting
tight against the wood at the top, the adhesive isn't going to carry
much shear - that will be carried by contact with the top of the J in
the recess. The resulting forces will be prying the channel out of the
recess. If you cover the bottom with a thin plate of Al, you can
reduce the stress in the adhesive significantly.
---------
| | <--- cherry
| __|
| |_______
| ||____ | <-- aluminum channel w/ squared J at top.
| ||| ||
| |||
| |||
| |||
| |||||
| |_ || <--- thin plate
| |||
| |||
-------
ASCII drawing limits details, but the channel should be a tight fit
in the routed groove and a thin plate has to be tightly in contact
with the channel.
It's worth the effort to weigh the mirror as assembled and get a feel
for the stresses. The contact stress at the top of the channel will
be the weight divided by 24Xdepth of routed groove in contact with
the Al. The shear stress in the adhesive if no routed groove is
used is weight/24X1. The force on the bottom of the channel pulling
out can be estimated (conservatively) as the weight times the
size of the J (in the direction from the frame to the wall) in turn
divided by the depth of the channel (top to bottom). Divide that
in turn by the number of screws holding the thin plate to see the
load per screw.
BTW - you might want to include a guess at forces that someone might
apply when cleaning the mirror and add that to the weight.
Compare those results with published data on contact and shear stress
in cherry, the shear strength of Al-to-epoxy and wood-to-epoxy and
the load capacity of little screws and make sure you're _well_ in the
safe zone.
Alternatively, look at it and decide whether you will trust it.
Personally, I'd prefer a mechanical connection to adhesive
unless you're dealing with some exotic adhesives.
Mike
"Robatoy" <[email protected]> wrote in message
news:[email protected]...
> Clapton sounded like an old
> man.
Clapton IS an old man.
Sand it. It will do just as well as the etching. Yes, screw it down then use
the epoxy. The epoxy alone would very likely hold it but the screws will
improve it substantially.
"Jim Bailey" <[email protected]> wrote in message
news:[email protected]...
> I have built a mirror frame from cherry. I am planning to use two pieces
> 24" of aluminum J-channel with one piece reversed, as a hanger at the
top -
> sort of a french cleat arrangement. I've recessed one of the pieces into
the
> frame. I was thinking of embedding it in West System epoxy to fasten it.
> Does anyone happen to know if West System does OK with aluminum without
> buying that 'etching' kit' from West ? Seems like a shame to spend that
> much money on that kit for a 1x24 hanger. I suppose I can just screw it
> down but I've only got about 3/8 depth there, after routing it out for the
> recess.
>
> Thanks
>
> jim
>
>
All excellent input guys. Thanks a lot !
I'm still in 'debating' mode with this. I've already routed the recess for
the one piece of J in the frame. Unfortunately I didn't notice the the hook
part of the J shape is actually a little longer than 1/2 way back to the top
of the J (if you can picture this at all). That means I can't simply hook
one over the other when I hang it, given that I've made the rout a pretty
close fit, unless I now go back and somehow grind/cut about 1/8 off that
short part of the J.
So anyway, I THOUGHT I had a good idea. Best laid plans .........
jim
"Jim Bailey" <[email protected]> wrote in message
news:[email protected]...
> I have built a mirror frame from cherry. I am planning to use two pieces
> 24" of aluminum J-channel with one piece reversed, as a hanger at the
top -
> sort of a french cleat arrangement. I've recessed one of the pieces into
the
> frame. I was thinking of embedding it in West System epoxy to fasten it.
> Does anyone happen to know if West System does OK with aluminum without
> buying that 'etching' kit' from West ? Seems like a shame to spend that
> much money on that kit for a 1x24 hanger. I suppose I can just screw it
> down but I've only got about 3/8 depth there, after routing it out for the
> recess.
>
> Thanks
>
> jim
>
>
In article <[email protected]>,
"Jim Bailey" <[email protected]> wrote:
> I have built a mirror frame from cherry. I am planning to use two pieces
> 24" of aluminum J-channel with one piece reversed, as a hanger at the top -
> sort of a french cleat arrangement. I've recessed one of the pieces into the
> frame. I was thinking of embedding it in West System epoxy to fasten it.
> Does anyone happen to know if West System does OK with aluminum without
> buying that 'etching' kit' from West ? Seems like a shame to spend that
> much money on that kit for a 1x24 hanger. I suppose I can just screw it
> down but I've only got about 3/8 depth there, after routing it out for the
> recess.
>
> Thanks
>
> jim
Oh, I think that roughing it up to give it some 'tooth' will suffice.
All the etching does is just that..and it cleans the aluminum.
Use a nice paper...like 80 grit. Then wipe with Methyl Hydrate. (DO NOT confuse
that with rubbing alcohol. Rubbing alcohol often contains lanolin..AKA grease.)
Drilling some small holes in the aluminum will allow some WEST to ooze through
and, in fact, make their own little fasteners..mushroom-style. Let gravity do
the shaping.
HTH
In article <[email protected]>,
[email protected] wrote:
> I think I would feel better about
> that then just glueing it on.
I thought that went without saying. The channel should be 'let in'.
PS.. I just listened to two cuts from the Cream reunion.
The 'boxed' set should be in the shape of a coffin. Clapton sounded like an old
man. (Don't get me wrong here..I also aspire to become a VERY old man.)
<[email protected]> wrote in message
news:[email protected]...
> Jim, bet you won't get anyone to touch this one. No one will want to
> be responsible if your mirror DOESN'T hold and they have given you bad
> advice. I cannot imagine you telling your SO that you explicity
> followed the instructions given to you by someone in Chatanooga for
> hanging your mirror.
>
> If there is any doubt, by the etching kit. It does two things: cleans
> the metal to remove all traces of hand oil, manufacturing oils, dust,
> dirt, etc. It also literally etches the metal to provide a grippable
> surface for the adhesive.
So will some 60grit sandpaper. It's not visible. Have at it.
Robatoy's idea of some holes is a good one too.
j
"J" <[email protected]> wrote in message
news:[email protected]...
> <[email protected]> wrote in message
> news:[email protected]...
>> Jim, bet you won't get anyone to touch this one. No one will want to
>> be responsible if your mirror DOESN'T hold and they have given you bad
>> advice. I cannot imagine you telling your SO that you explicity
>> followed the instructions given to you by someone in Chatanooga for
>> hanging your mirror.
>>
>> If there is any doubt, by the etching kit. It does two things: cleans
>> the metal to remove all traces of hand oil, manufacturing oils, dust,
>> dirt, etc. It also literally etches the metal to provide a grippable
>> surface for the adhesive.
>
> So will some 60grit sandpaper. It's not visible. Have at it.
> Robatoy's idea of some holes is a good one too.
>
> j
>
>
A word of caution when bonding aluminum: Time is your enemy!
I believe the main purpose in etching and/or mechanically and chemically
cleaning is to remove the surface oxide layer. Since aluminum is reasonable
reactive, this layer will reform in a short time, therefore the important
thing here is to prep the aluminum just before you apply the adhesive.
A second word of caution: Epoxy needs a gap!
Unlike wood glue, when bonding with epoxy, it's best to have a gap. If I
was to bond aluminum to aluminum, I would most likely add micro spheres
(about 0.005" dia.) to the mix to give me the gap. With wood, one might
argue that the wood pores give you the gap, but I'm not sure. That 60 grit
paper sounds like it would give some reasonably deep scratches which is a
good thing.
Disclaimer: I don't have any experience structurally bonding aluminum to
cherry (or any other wood) so others may give you better advice.. Now if we
were just talking about beryllium....
Bill Leonhardt
On Mon, 05 Dec 2005 14:37:11 GMT, "Jim Bailey"
<[email protected]> wrote:
>Does anyone happen to know if West System does OK with aluminum
Depends on the aluminium, the alloy and (mainly) on whether it has been
anodised. I wouldn't expect it to work unless you prepare the aluminium
surface first. A rub with silicon carbide (black) abrasive paper will
remove the anodising - softer abrasives may not be so successful
(they're only aluminium oxide themselves!)
"Jim Bailey" wrote:
>I have built a mirror frame from cherry. I am planning to use two pieces
>24" of aluminum J-channel with one piece reversed, as a hanger at the top -
>sort of a french cleat arrangement. I've recessed one of the pieces into the
>frame. I was thinking of embedding it in West System epoxy to fasten it.
<snip>
You have one chance to do this job and have it hold.
AS has been suggested, drill lots of 1/8"-3/16" thru the aluminum, then
rough up the surfaces, front and back with some 36 grit paper on a right
angle disk sander.
Next apply a layer of 6 oz glass, wet out with epoxy on both sides,
allowing 24 hours to elapse between fromt and back glass.
Allow to cure are about 5-7 days, then sand smooth, trim excess glass.
You can now epoxy the cured glass to the wooden frame, and it will hold
because you have trapped the aluminum in glass and then bonded glass to
wood.
I wouldn't bet any real money on something else.
Lew