Re: Biscuts versus glue joint bit opinion wanted

Its always interesting to see what statements will cause controversy.

I have not done any purely scientific tests but I did once have the
opportunity to do karate kicks of glued up panels some of which were
edge butted and some were T&G. The T&G's seemed about twice as hard to
break.

Yes, everyone has bought into the concept that a well executed ***
glue joint with modern wood glues is stronger than the wood.
Interestingly in the case of PVa types (like Titebond II) there are
really only generally accepted therories about how it actually bonds
but no real provable science at the molecular level, just via physical
testing. However, break apart any *** glued joint, or any joint for
that matter and you'll see the wood fracturing in some places and the
glue joint breaking in others.

Things to consider in the non-perfect world we live in.

1. Strenght of the glue joint: Imperfections in the glue joint may
cause weak spots so some mechanical advantage could add strength.

2. Strength of the wood: Even if you just consider the wood strength,
involving the tongue of one piece inside the groove of another can
compensate for any weak areas in the grain of either. Where one might
split from direct downward force, the other might be strong enough to
hold

3. Strength of the glue joint (again): With a much expanded surface to
surface connection between the mating parts, at least double I assume,
you have greatly increased the odds of good contact all along the
joint. You have greatly lowered the possibility that the two pieces
are joined at a coincedient weak point.

Adding a spline with an opposing grain orientation will add even more
strength than the tongue concept and still includes the benefit of
added glue surface area.

BW


On Oct 31, 7:32 am, Chris Friesen <cbf...@xxxxxxxxxxxxx> wrote:
SonomaProducts.com wrote:
If you are doing a panel glue up a simple edge *** joint will do fine
if milled and clamped correctly, biscuits will help with alignment and
a T&G type joint will be much stronger.

Are you sure about that?

It's accepted fact that a properly executed glue joint is stronger than
the surrounding wood. Given that any failure will already be in the
wood rather than the joint, how can a T&G type joint be any stronger at all?

Chris


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