From: bennett@adobe.com(Bennett Leeds)
Subject: Re: dowels vs dados vs t&g
Reply-To: bennett@adobe.com
Organization: Adobe Systems Incorporated
Distribution: na
Date: Tue, 15 Dec 1992 18:27:58 GMT

David Kosenko writes
> For building rail and panel doors and cabinet face frames, biscuits are
> useless (I have a biscuit cutter btw) because, at least for mine, the frames
> are too narrow for even a #0 biscuit. 

Agreed. There are two possible solutions here. 

First, Lamello makes a smaller diameter "face-frame" blade. I forget the 
model number, but Highland Hardware sells it. It takes a new size of face
frame biscuit, which is shorter than a #0, but much deeper. The blade 
fits many joiners (it doesn't fit the PC, and you have to bore a differently
sized hole for the Ryobi). The Lamello joiners even have the depth setting 
for it marked already. The blade is pretty expensive, though.

The second is to use Woodhaven's round biscuits. The slots are cut with
a router (typically used in a table), and are about 1.5" in diameter (quite
short - a #0 biscuit is about 2" long). They've recently changed their biscuit 
material - instead of chipboard it's now a "grainless compressed wood fiber 
composition board." I don't know how strong it is relative to the compressed
beech most biscuits are made out of.


> I suppose they could be used for assembling the carcass (I prefer dados
myself)...

Dados and rabbets take longer to cut, you need to be more accurate in 
cutting them, and I'll argue that the final joint is not as strong as 
a biscuited joint.


> Btw, my dowelling jig (a Stanley) requires the same sort of pencil mark
> needed for a biscuit cutter, i.e. "an itty bitty pencil line."

But you need to be "dead on" with the dowelling jig. With biscuit joiner,
there's at least an 1/8" of longitudal slop, so if you miss the line by
a hair or more, the joint will still go together with strength.


> For the records, I also used mortice and tenon joints on some of the door
> frames, but with no tennoning jig, I was not happy with the precision of
> the fit. 

You don't need a tenoning jig to cut accurate tenons. What's important is
that the width of the tenon fit the width of the mortise snugly. This means
you cut the mortise first (by hand, hollow chisel in drill press, router,
etc.). You can cut the tenon on a tablesaw or RAS outfitted with a dado
blade (or even a regular ripping blade). You use the miter gauge and hold
the piece horizontally. Use the rip fence to set the length of the tenon.
Take as many passes as needed on each side. Do it on scrap of the same
thickness first and fine tune the blade depth until the tenon thickness
is right. If you don't have a tablesaw/RAS, you can make a jig to do this
with a hand-held router - the principle is the same.

It is surprisingly easy to cut strong mortise and tenon joints. Just cut
the mortise first, then cut the tenon to fit.


> Dowelling seems to me the best solution for this particular
> application.

Dowelling is my least favorite joint. It's difficult to get the holes to
line up precisely - and if you're off the joint won't go together or you'll
be placing stresses in the wood. The drilling creates discontinuities in the
boards being joined, which are stress points that will break. There isn't 
very much long grain to long grain gluing area. About the most you can say
for dowelling is that it enables you to design the piece as if it were built
using butt joints, it's stronger than butt joints, and doweling jigs are 
cheaper than biscuit joiners (but not cheaper than a mortising chisel).

All IMHO, of course,
-Bennett Leeds
bennett@adobe.com
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