I am making an extension wing for a tablsaw using MDF. I gluing Formica
to the surface using contact cement. It will be screwed to a frame made
of 3/4" x 2 1/2" maple boards. If I don't seal the bottom of the MDF,
will it warp? My basement shop keeps pretty dry. I know the MDF will
absorb moisture faster on the unsealed bottom making it warp, but the
question is, will the frame boards be stiff enough to overcome that
tendency?

Thanks,

Bill

Bill Calbert writes:


I am making an extension wing for a tablsaw using MDF. I gluing Formica
to the surface using contact cement. It will be screwed to a frame made
of 3/4" x 2 1/2" maple boards. If I don't seal the bottom of the MDF,
will it warp? My basement shop keeps pretty dry. I know the MDF will
absorb moisture faster on the unsealed bottom making it warp, but the
question is, will the frame boards be stiff enough to overcome that
tendency?

I did one like that about 4 years ago. A friend has it now and there has been
no warping, 2 different shops, fairly humid area in summer (central VA),
neither shop with AC.

Charlie Self
"Take care of the luxuries and the necessities will take care of themselves."
Dorothy Parker

http://hometown.aol.com/charliediy/m.../business.html

Seal the edges and both sides. Even if you don't have enough material
(Formica) to do the edges and bottom, seal them with poly or some shellac or
an enamel paint (use oil primer first though).

Whether the maple boards will keep it from warping is not the question. The
frame is to keep the top flat and rigid as a work surface, the Formica or
other surface sealant will keep the moisture out so the MDF does not swell
and cause the top to distort - especially along the edges.

Bob S.



"Bill" wrote in message
news:WNGNb.77747$na.43120@attbi_s04...
I am making an extension wing for a tablsaw using MDF. I gluing Formica
to the surface using contact cement. It will be screwed to a frame made
of 3/4" x 2 1/2" maple boards. If I don't seal the bottom of the MDF,
will it warp? My basement shop keeps pretty dry. I know the MDF will
absorb moisture faster on the unsealed bottom making it warp, but the
question is, will the frame boards be stiff enough to overcome that
tendency?

Thanks,

Bill

"Bill" wrote in message
news:WNGNb.77747$na.43120@attbi_s04...
I am making an extension wing for a tablsaw using MDF. I gluing Formica
to the surface using contact cement. It will be screwed to a frame made
of 3/4" x 2 1/2" maple boards. If I don't seal the bottom of the MDF,
will it warp? My basement shop keeps pretty dry. I know the MDF will
absorb moisture faster on the unsealed bottom making it warp, but the
question is, will the frame boards be stiff enough to overcome that
tendency?

Thanks,

Bill


I don't know if your top will warp but my Delta extension table warped
pretty bad. I am not sure of the exact model of the table but it came with
a Unisaw with 50" Biesmeyer fence. It had a pronounce crown where it met
the saw. I had to sand the laminate off in a fairly large area get it flat.
Now I have to wax the table to insure that wood slides without too much
friction.

Bob McBreen - Yarrow Point, WA

"Bill" wrote ...
snip will it warp?

Nope. My table saw's side extension is made like that and it's 10 years old
and has lived in both dry and very humid locations around the continent.
Still flat.

--

Cheers,
Howard

----------------------------------------------------------
Working wood in New Jersey -
Visit me in the woodshop - www.inthewoodshop.org

Howard Ruttan wrote:
"Bill" wrote ...

snip will it warp?


Nope. My table saw's side extension is made like that and it's 10 years old
and has lived in both dry and very humid locations around the continent.
Still flat.


I'm on my third extension in 7 years. The first two I made out of
particle board. The first I just laminated the top. The second I
laminated every side. Both warped. The third one I made out of birch
plywood a few months ago. I'm hoping that stays stable. In defense of
the particle board, I live in a suburb of New Orleans. It gets a little
humid here .

Andrew Robinson