On Mon, 30 Jul 2007 11:14:42 -0700, FoggyTown wrote:


I think that you've just answered your own question... unless dowels are
considered Mechanical Fasteners..

mac


No, a dowel is not a mechanical fastener. Screws, nails, brads,
clips, etc. are.

Let me try restate the question.

In a project where screws would normally (and acceptably) be used to
attach one piece of wood to another, is there anything lost (i.e. in
strength or structural integrity) in using glued dowels instead of
screws?

FoggyTown

Well, let me do the usual disclaimer that I'm not an expert, for sure...

It would seem to me that a well fitted dowel with grooves for glue flow would be
stronger than a screw in most cases....
The main advantage to a dowel or biscuit, IMO, is the increase in gluing area...
because if the joint fails, screws aren't going to help much...

I've done test joints with biscuits and then taken them apart a week later... In
every case I had to break the joint before the biscuit let go..



mac

Please remove splinters before emailing

"dpb" wrote in message ...
George wrote:

"FoggyTown" wrote in message
ps.com...


Removal resistance. The dowel does just fine in shear, but pullout is
about nil.

That depends on grain orientation -- if it isn't cross grain, there's a
pretty good area for glue joint which isn't 'nil'. Although I've never
done a calibrated test, in end grain which where the dowel would have the
most long-long grain, the screw might not have any more holding power, if
as much, knowing that they'll tend to pull out of end grain...

Would be an interesting test just out of curiousity...


It's been done. See Hoadly on differential wood movement along the grain of
the dowel and the wood which encloses it. Unless you've got the perfect
grain match, it'll work loose from the glue as time passes, the wood cycles
and the glue becomes more brittle.

I have quite a few pieces of Stickley which have, in addition to
exposed tenons, visible tenon-pin dowel ends, some of which are of
contrasting wood. Also some with visible dowel pins in corbels. All of
these dowel ends are prominent - no attempt was made to match grain.
It's a feature of A&C furniture.


There is also a difference between a pin and a plug. A pin is a structural
component with the grain oriented *through* the cylinder, intended to
provide sheer resitance to pullout of a tennon. A plug is a cross-gram
cosmetic cap used to cover a structural component (screw).

You cant "match" the grain on a pin because it is, by definition, in the
wrong orientation.

I believe that the OP intended to use dowels as a loose tennon rather than
to pin a (not loose) tennon.

Steve



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