If the wood breaks before the joint breaks, it makes no difference. That is
the case with good wood glue or epoxy.
In general, epoxy is a stronger adhesive than most wood glues, but unless
you have certain other reasons to use one over the other, base your decision
on ease of use.
If waterproofness is NOT an issue, then it doesn't matter. Wood glue
properly applied is gonna be as strong as the wood, so what do you gain
by spending more $$ for epoxy, plus cleanup is no fun.
Dan O'Connor wrote:
the answer is "Yes".
Or alternatively, "No"
Everything depends on:
(1) the particular glue involved
(2) The type(s) of wood, and/or other materials, involved
(3) The type of joint
(4) The quality of the fit
just for starters.
In general, with a precise fit between the pieces, _any_ quality glue,
*USED*PROPERLY*, will be _significantly_ stronger than the surrounding
wood. "How much stronger" is essentially a moot point, since the wood
next to the joint *will* fail before the joint itself fails.
There are some 'fundamental' considerations, like it's usually a Bad Idea(TM)
to use a water-based glue on materials that will suffer adverse effects from
exposure to water (e.g. MDF, cheap particle-board, etc.)
I don't disagree with anything you said. But joint strength has many dimensions;
how long will the joint stay strong, how does the adhesive react to wood
over time, the dowels in many chairs are well fitted at the factory, still those
joints almost always fail after a while; which adhesive will minimize this
glue joints in plywood seem to always fail near the edge if it shows; is this
independent of the adhesive used? I think the issue is more complex then you
He didn't ask about joint strength. :)
Joint strength is a complex issue. with _what_ 'adhesive used' being a
relatively -minor- consideration.
"uniformly badly" -- pretty much regardless of the type of glue used. :)
Again, *almost*always* it is _not_ the glue that fails. the wood fiber
_itself_, NEXT TO where the glue is, gets torn.
Have you noticed any consistency in the type of glue used in the failures
_you've_ seen? <grin>
"Interior" grade ply _is_ subject to ply separation in the presense of
moisture. Airborne humidity can 'wick in' at an exposed cut edge, which
structurally weakens the ply, so the wood 'tears' easier.
Note that this has -nothing- to do with the glue used for the _joint_ itself. :)
The 'mechanics' of joint failure *is* a complex issue, no doubt about that.
The type of glue used is usually _not_ a significant factor. Other issues,
primarily 'joint design', 'joint loading', 'fit', 'surface preparation', and
'proper application of the adhesive', among others, tend to dwarf it.
A _real_ 'hide glue' -- the variety you have to keep in a hot pot -- has
an excellent combination of "stick-to-it-iveness", surface penetration, and
flexibility. OTOH, it is a *bitch* to prepare and keep ready, requires con-
siderable knowledge and 'care' in application, and has to be used in a timely
manner. Virtually all modern adhesives are 'inferior' in one way or another,
but (more than) make up for that inferiority in 'ease of use'.
Not totally true because some polyurethane and epoxy glues are developed
with a large degree of flexibility
Not one mention of polyurethane glues or methylmethacrylate glues yet ...
keep going everyone
And glue type does have a significant factor in joint failure where the wood
fibres tear next to the joint, how far the glue penetrates in to those
fibres is dependent on the viscosity of the glue. Moisture curing adhesives
like gorilla glue will seek out the moisture in the wood and penetrate
further, bonding with the moisture and reinforcing the surface fibres (don't
get me started on the mechanics of surface fibres ;-).. ), thus making a
stronger joint, generally speaking, but stronger than what? what are we
comparing it to?.
as some have mentioned, there are literally many glues types with hundreds
of variations of those glue types as well as different woods behaving in
different ways and your question (The OP) was just a wee bit too general to
give an answer to. ;-)
Either. Both are stronger than the wood they bond.
If the project might get wet/stay moist, use epoxy and a good finish.
Iguana: The other green meat!
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