"Agki Strodon" wrote in message hlink.net...
"Leon" wrote in message
m...

"Agki Strodon" wrote in message
news:4TCEc.20861$bs4.13057

Spaces in glued up joints produce weakness because theres no glue in the
spaces to form a bond.

Now you are showing signs that you might understand the point that I was
trying to make.

You said,

"A roughed up surface holds better than a smooth one because there's more
glue in the between pieces volume, ain't it?"

Roughed up surfaces often cause spaces in the glued up joint. A smooth
surface is Ideal for glue.



That is really debatable, mein Herr. It depends. If the glue can get into
the roughed up spaces, it will be stronger because there will be more glue
in the joint as a result of the increased surface area caused by the
roughening up.

I think it depends on how rough and what sort of glue. With most any
glue but epoxy the roughness must be small enough that you have a very
thin layer accross the interface. If you roughen the surface to the
point that the glue is filling gaps the result will be a weaker
joint than if you just planed the surfaces smooth and glued them
because the glue in the pockmarks will be weaker than the wood it
replaced. I dunno where you cross the line between giving the glue
tooth, and weakening the joint by requiring the glue to fill a gap.

I _think_ that a planed or scraped surface has the correct level
of roughness for most glues, and does not have as many loose fibers
or dust particles in the pores and does a surface roughened with
sandpaper.

With epoxies, the glue in gaps is stronger than the wood and the
strength can be maximized by eliminating the wood altogether, though
the resulting furniture may leave something to be esthetically desired.

--

FF