Desk Top Construction

Tyke wrote:

> If you go the 5"-6" method, I would consider gluing a board across the
> 36in depth at both ends and one in the middle of the 119" span.

That's crossgrain gluing and is a recipe for disaster.

How about putting all the boards with the tree center up. That way they
all bow, if at all, in the same direction and can be held down with one
or two screws in the middle and a screw in an elongated slot at front
and back (and anywhere else you'd like).

--
It's turtles, all the way down

Richard Holub wrote:
> I plan on building a built-in desk top to a section of my office room
> (36" x 119"). What is the best/strongest way for cutting and gluing?
> I am not a master woodworker...this is just a hobby.
>
> 1---cut boards 2"-3" in width and flip end to end or flip side to
> side?

More important IMO is laying them out so they look nice. The idea for
flipping is that by alternating the direction of the annular rings any
tendency to cup in one board will be offset by its neighbor's tendency
to cup in the opposite direction. Not a big deal IMO...especially with
boards 2-3" wide.

Flipping either way accomplishes the same thing as far as annular rings
go.
______________

> 2---glue and clamp edges with a straight cut, tongue & groove or
> biscuit joinery?

Any of the above. If the edges are good no sort of mechanical joint is
needed...mechanical joints aid in alignment of the edges, don't do squat
for strength.
________________

> 3---considering the length of the boards, should there be any
> reinforcing cross-piece somewhere along the bottom other than the
> support framing?

Depends on the size of the aprons (framing), their construction, what
sort of weight might be on them and where it might be.


--
dadiOH
____________________________

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OK dadiOH, now to disect this a little further...

> More important IMO is laying them out so they look nice. The idea for
> flipping is that by alternating the direction of the annular rings any
> tendency to cup in one board will be offset by its neighbor's tendency to
> cup in the opposite direction. Not a big deal IMO...especially with
> boards 2-3" wide.

OK, so would it be ok to leave the boards at let say 5"-6" in width/ This
would give me less work with gluing.

If the edges are good no sort of mechanical joint is needed...mechanical
joints aid in alignment of the edges, don't do squat for strength.

I was under the impression that mechanical joints (e.g. biscuits) are used
in furniture construction just for that purpose, strength?


> Depends on the size of the aprons (framing), their construction, what sort
> of weight might be on them and where it might be.

I was planning on puting aprons all around the desk top. Perhapps 1.5"-2"
in front/back and 4"-5" at each end.

"Tyke" wrote in message

> If you go the 5"-6" method, I would consider gluing a board across the
36in
> depth at both ends and one in the middle of the 119" span.

You will definitely want to reconsider doing that.

Wood expands/contracts across the grain and "gluing a board(s) across across
the 36in depth" (across the grain) will eventually end up in grief due to
the inevitable wood movement, and will do little for sag across the 119"
span.

His proposed apron should protect him from sagging, which I am assuming he
was worried about because of the 119" span.

He also needs to be aware of how he fastens the desk top to the propoosed
aprons.

There are many methods to do this, but figure eight fastners are readily
available that will allow his glued up desk top to expand and contract while
holding the top securely to the underpinning aprons.

Rockler also sells a table top fastener that fits in a slot, and allows for
expansion/contraction.

http://www.rockler.com/findit.cfm?page=784

--
www.e-woodshop.net
Last update: 12/13/05

Richard Holub wrote:
> OK dadiOH, now to disect this a little further...
>
>> More important IMO is laying them out so they look nice. The idea
>> for flipping is that by alternating the direction of the annular
>> rings any tendency to cup in one board will be offset by its
>> neighbor's tendency to cup in the opposite direction. Not a big
>> deal IMO...especially with boards 2-3" wide.
>
> OK, so would it be ok to leave the boards at let say 5"-6" in width/
> This would give me less work with gluing.

Too many variables to say...type of wood, where you live, etc.

I made a round, 48" white oak breakfast table 3-4 years ago - boards are
all 5-6" wide x about 7/8". No problem with it and I live in central
Florida. Top is *very* solidly attached to the aprons though.
________________

> If the edges are good no sort of mechanical joint is
> needed...mechanical joints aid in alignment of the edges, don't do
> squat for strength.
>
> I was under the impression that mechanical joints (e.g. biscuits) are
> used in furniture construction just for that purpose, strength?

Nope. A decent glue joint is stronger than the wood. Wanna buy a glue
joint bit? How about a wedge T&G one? :)
______________

>> Depends on the size of the aprons (framing), their construction,
>> what sort of weight might be on them and where it might be.
>
> I was planning on puting aprons all around the desk top. Perhapps
> 1.5"-2" in front/back and 4"-5" at each end.

You still haven't said what thickness the top is to be or type of wood.
Regardless, the front/back aprons are pretty skinny and I'd use at least
one, probably two cross pieces for something that long with that sort of
frame. Personally, I'd use the 4-5" aprons everywhere and put in some
drawers (what's a desk without drawers?). The frame pieces for drawer
runners could also serve as cross reinforcement. Even if you didn't
make drawers, I think aprons all the same size would look better. The
wider aprons would allow more area to attach the legs as well.

Regarding attaching top to aprons, unless the top is ply you have to
allow for expansion/contraction of the top...you cant just glue/screw it
to the aprons. The conventional way to do that is with little steel "L"
brackets...one side fits in a dado on the apron, other side is has a
hole in it and is screwed from underneath into the top. Easy to make
your own "L" brackets out of hardwood. My breakfast table has very
stout oak "L"s through bolted into 1/4" threaded brass inserts in the
bottom of the top. The other side of the "L"s hook under a 1/2 x 1/2
oak strip glued to the backs of the aprons about 1/16 below the top.

A nicety when attaching the top is to have the top edge of the aprons
beveled very slightly inward so that the top contacts just the outside
edge. Otherwise, it is easy to get gaps twixt top and apron.

--
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

Going to the 5"-6" width of board could run the risk of cupping. Note it is
a risk not a definate. Depends on how the board was cut (quartersawn,
riftsawn etc.) the humidity of the wood at the time of construction and the
humidity of the office after placement.

If you go the 5"-6" method, I would consider gluing a board across the 36in
depth at both ends and one in the middle of the 119" span.

Aprons all around will look good and make the top appear thicker. If you go
with the crossways boards for stability, aprons will hide this fact while
looking good.

Biscuits will not add to the strength of the joint. I do not have a biscuit
cutter. I either use dowels which provide alignment vertically and
horizontally, but take a lot more time than biscuits, or I cut a slot in
each piece and use a 1/4in plywood strip as a continuous biscuit. I have an
adjustable slot cutting and so can make the slot fit the actual thickness of
the slot.

I expect your boards will not be exactly flat. Using the continuous slot
biscuit will minimize vertical alignment deviations which will reduce final
sanding efforts.

Dave Paine.

"Richard Holub" <[email protected]> wrote in message
news:[email protected]...
> OK dadiOH, now to disect this a little further...
>
>> More important IMO is laying them out so they look nice. The idea for
>> flipping is that by alternating the direction of the annular rings any
>> tendency to cup in one board will be offset by its neighbor's tendency to
>> cup in the opposite direction. Not a big deal IMO...especially with
>> boards 2-3" wide.
>
> OK, so would it be ok to leave the boards at let say 5"-6" in width/ This
> would give me less work with gluing.
>
> If the edges are good no sort of mechanical joint is needed...mechanical
> joints aid in alignment of the edges, don't do squat for strength.
>
> I was under the impression that mechanical joints (e.g. biscuits) are used
> in furniture construction just for that purpose, strength?
>
>
>> Depends on the size of the aprons (framing), their construction, what
>> sort of weight might be on them and where it might be.
>
> I was planning on puting aprons all around the desk top. Perhapps 1.5"-2"
> in front/back and 4"-5" at each end.
>