cut to length and lap joint in one pass

[alexy]

Is this a dumb idea?

I have a bunch of 3/4" x 3/4" sticks to miter at various angles and join at their ends with lap joints. I am thinking about using my 7" dado set on my table saw, replacing the right-hand blade with a 10" saw blade. Then I can in one pass miter cut the stick to length and cut the mitered lap joint. But I haven't seen that technique mentioned before, which makes me worry that I am missing a real negative.

BTW, I would probably make a new ZCTP for this blade combination. BTW^2, it is a right tilt saw, so the 10" blade would be closest to the arbor.

Thoughts anyone?

[tom]

Will the teeth of the adjacent chipper clear the 10 incher? Tom

[Charley]

I haven't tried this, just doing some thinking about the possibilities:

I think you are going to have tooth interferrence between the teeth on the dado chipper blade and the side of the saw blade. The chipper teeth are wider than the body of the chipper and will prevent you from tightening the arbor nut without bending or breaking the chipper teeth. You may get away with putting a thin spacer washer between the chipper and the saw blade to keep them apart just the right amount, but that's going to be a pretty difficult spacer to find as it will need to not only be the right thickness but precision ground for flatness.

[alexy]

Good question. I may have to add shims to make sure that happens.

[Lobby Dosser]

If the correct length is the end of the lap and you add shims to clear the

10" blade (set on the teeth?), the lap will not be complete to the end of the stock.

There are so many risk factors in this that it doesn't seem worth the effort.

[alexy]

You (and Tom) are right there. I had not thought about that.

Actually, it's very easy to find--the outside cutter from the dado set. Not sure why I was thinking of replacing that with the saw blade. The dado set outer blades are hollow ground thin-rim steel, with blade thickness at the center equal to the kerf. I'd put a very thin shim between the dado outside blade and the 10" carbide saw blade to make sure the dado's teeth were not interfering, but keep the shim thin enough that the outside edge of the dado cutter is within the kerf of the saw blade. Then build up the dado set enough to give my 3/4" lap.

[alexy]

Well the goal of the buildup would be to have the outer edge of the dado blade within the "shadow" of the carbide teeth on the saw blade.

And it's those risk factors I'm trying to assess. Thanks for your thoughts.

[Joe Gorman]

As you mentioned miters at various angles you have to take the diagonal length of the joint into account. A 45° miter needs almost 1" of dado blade to cut, this figured with a wooden desk ruler and no reliable square reference. Joe

[alexy]

Spoil-sport! Seriously, this may well be a deal-killer. I'll have to figure it out when I determine the miter angles I will need. Thanks; you may have saved me a dope-slap from discovering this after spending time to set up the saw and make a test cut.

[WoodButcher]

I was scanning some old Wood mags last nite and saw almost this exact same thing. In the Dec2000 issue, pg 32 the reader tip was to install 1/4" of dado blades spaced 1/4" from his normal blade with a piece of ply. He was cutting drawer sides to width and cutting the dado/groove for the bottom on the same pass. The editors raised no safety concerns and voted it the "Top Shop Tip" of that issue.

Art

[B A R R Y]

As long as the blade is 90 degrees to the table, I don't see problems.