C & S wrote:
I just received FWW 194 in the mail. The article "Get Serious About
Clamping" attempts to tell us that we are all underclamping our
work. While Roman Rabeij chose not to "blind us with the science" he
makes the assertion that we really ought to have 1200 lbs/sq inch of
clamping force to glue together flatsawn sugar maple. That was not
even the optimal number, that's his recommended number. Please
please please, just show us the graph with the sweet spot of glue
joint failure to clamps required.
My main bench is 3 inches thick and about 6 feet long. Am I going
to have to scrap my bench because I did not apply 259,000 lbs of
pressure when assembling those laminations? I have a pretty decent
clamp collection and I think I could get about 15% of the way there
with about every clamp I own (those fancy bessy's are only good for
370 lbs of squish y'know).
*** as an asside, he claims that het gets more clamping pressure
(470
lbs.) out of a quick-grip clamp than a parallel jaw (Cabinet
Master/Bessy)) clamp. I find that a bit hard to swallow.
My take on the article, on the whole, was that his uncited "science"
does not jive with my practical experience. I have never had a glue
joint failure that could not be attributed to sloppy joinery :-}.
Rabeij's conclusion is akin to saying that we should all drive a
$259K Bently because Bently can make a better sedan than Honda.
What say you?
A quick look at the FPL handbook(
http://www.fpl.fs.fed.us/documnts/fp...tr113/ch09.pdf ) reveals
that the recommended clamping pressure range is 100-247 psi, with
further notes that this depends not only on the density of the wood
but also on the viscosity of the adhesive and the quality of the
surface, and that too thin a glue line is as bad as too thick, with an
optimal thickness of .003-.006 inches.
Now it might be that he's bonding with some ancient almost-dried-out
Titebond that gives him a good glue line at the pressures that he's
using or it might be that he has access to some newer research or it
might be that he's full of crap.
Personally though, given the choice between Forest Products
Laboratories and the unsupported opinion of some unknown art
professor, I'll take FPL.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)