In article k.net,
Edgar Svendsen wrote:



wrote in message
ink.net...
In article ,
Dan O'Connor wrote:


Anyone??
"Dan O'Connor" wrote in message
...
What is stronger for bonding pieces of wood: Epoxy or Wood Glue?





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;

He didn't ask about joint strength.

Joint strength is a complex issue. with _what_ 'adhesive used' being a
relatively -minor- consideration.

how long will the joint stay strong, how does the adhesive
react to wood shrinkage over time,

"uniformly badly" -- pretty much regardless of the type of glue used.

the dowels in many chairs are well
fitted at the factory, still those doweled joints almost always fail
after a while;

Again, *almost*always* it is _not_ the glue that fails. the wood fiber
_itself_, NEXT TO where the glue is, gets torn.

which adhesive will minimize this effect? The glue joints
in plywood seem to always fail near the edge if it shows; is this effect
independent of the adhesive used?

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.

I think the issue is more complex then you
implied.

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'.