Mortiser Bit

[Eddie Simmons]

Just got a G0448 mortiser today and try to use it. Brought a 3/4 mortise bit and tried it on some red oak. It worked okay but have a few question about how far to extend the auger bit below the chisel bit? Also if you are making a 2 inch wide mortise would you start with a smaller bit and then work you way up?
Thanks
Eddie

[Frank Drew]

Eddie,

The bit extends just a bit past the end of the hollow chisel (a sixteenth or so), enough so that it neither fouls the chisel nor clogs with chips between it and the chisel. Others may supply more exact measurements.

To cut a 2" wide mortise I'd cut two 1/2" or 3/4" mortises at the outer margins, leaving wood between, then waste the in between portion. In cutting mortises, it's best the have the chisel supported by wood on both sides, so that it doesn't drift into the open space.

[glenn bradley]

And keep your chisel really, really sharp. Brand new in this case means, ready for honing ;-)

[Lee Schierer]

And keep your chisel really, really sharp. Brand new in this case means, ready for honing ;-)

I second Glenn's comment regarding honing. I couldn't belive the difference it made after I honed the outside surface of my chisels to make them smoother. The cut like butter after that. I find that I can overlap my cuts about 3/4 of the chisel width with no problem. I always do both ends of a long mortice and then work toward the other end when making long slots. If you have a small amount of wood left to remove, center it under the tip of the drill.

Use a fence to keep long mortices aligned and make sure the bit is parallel to the sides of the mortice.

[Neal Clayton]

also when doing mortises in multiple passes like that, do the outside edges first. any opportunity for the board to flex will introduce inaccuracy. cut the edges that need to be accurate first, cut the middle waste after.

even a very stout mortiser will struggle to remove less than 1/8 of material accurately.

[Josiah Bartlett]

The easy way to set up the chisel consistently is to first install the chisel with a shim between the shoulder of the chisel and the receiver in the tool. Then bottom out the bit in the chisel, tighten the chuck, and then loosen the chisel, take out the shim, and tighten it up. I use a dime for mine and it seems about right. A feeler gauge would be more accurate, I suppose.

[Peter Quinn]

A little trick to make your life easy? Chuck the chisel with a 1/16" or so shim between the base of the quill that holds it and the base of the chisel's shoulder. Then chuck the drill bit flush with the chisel using a scrap board on the table and pulling the lever down until the chisel just makes contact, tighten the drill chuck, release the lever, loosen the chisel, remove the shim and raise the chisel to fully seat it against the quill. Done, you now have a perfect offset, no measuring or hunting and pecking. I knew a guy that had a small stack of playing cards to do this to tailor the back set to what ever work he was doing. Some things he liked a bit more, some a bit less. Much easier to do than explain.