Delta Mortiser - Bit Clearance

[joeljcarver]

The Delta Mortiser instruction manual says the clearance between the chisel and bit should be between 1/16" and 3/16" --- depending on the type of wood. In the past, with a drillpress mortising attachment, I've always set the clearance at about 1/16". From your experience, which species of wood require the larger clearance?

Joel

[John Martin]

3/16"? I guess I'd ask Delta. I won't pretend to know more than they do about mortising chgisels and bits, but it sounds like a misprint to me. I usually set mine around 1/32" - jst enough to keep the bit from rubbing.

John Martin

[Leuf]

I haven't used it much yet, but with the 1/4" chisel in hard maple I had to set it to at least 1/8" or else the chips would just jam up the bit.

-Leuf

[charlie b]

The bit in hardwood will make fine shavings. In soft wood you frequently get the grain to tear rather than be shaved. If you leave a bigger gap between the chisel and the bit you're apt to have the bit deflect in the cut - and leave room for chips to jamb between it and the chisel.

Here's The Forty Cent Method for bit to chisel gap.

if you tune up the chisel and bit - sharpen and polish - you'll get less wood tearing and clogging things up.

charlie b

[Mortimer Schnerd, RN]

I use the 40 cent method on my mortiser.

[Edwin Pawlowski]

You MUST tune up the chisel and bit. They are NOT sharp from the factory. Lee Valley sell a tool for doing the inside of the chisel. Hone the sides on stones as you would any cutting tool. A small file will do the side of the bit.

[joeljcarver]

and bit should be between 1/16" and 3/16" ...

have the bit deflect in the cut - and leave room for chips to jamb between it and the chisel. ...

I was planning to machine some steel shims to the right thickness, but the Forty Cent Method sounds a lot cheaper.

wood tearing and clogging things up.

I had a conical stone on a shaft, but it seems to be on a long vacation. I'll get the Lee Valley set-up -- and file the inside corners a bit.

Thanks again, Charlie.

Joel

[Michael Faurot]

I saw the original post suggesting the stuff from Lee Valley, but when I tried poking around their web site, I didn't see it myself. Would you post a URL for this tool?

Thanks!

[Edwin Pawlowski]

item on the page.