Benchtop Mortising Bits

[Denny Rice]

I have had a Steel City benchtop mortising machine for about two years now and have had some problem with the bits for the machine. They seem to not last as long as you think they would... When I use the machine I take small steps into the wood and back the bit out to clean the mortise out and go at it again, but the bit seems to get extremely hot no matter what I do. Is there anything I can buy to spray on the bits before or while I am using the machine to keep the bits from getting so hot? Thanks.

[Jim McFarland]

1st thing would be to make sure the bit is properly adjusted to the chisel. Lee Valley offers these instructions for adjusting and they have worked for me:
http://www.leevalley.com/shopping/Instructions.aspx?p=54295

[Rick Dennington]

Denny: First of all let me say do not spray anything on the bits. Whatever you spray(i.e. water, oil, lubricant, etc.) will drip down and soak into the wood, even if you think you cleaned the outside, its still inside where the bit is. You didn't say what wood you're mortising, but hardwood like oak or walnut is so hard it will cause the bits to get warm or hot. Make sure the bit is all the way in the chuck. Push the chissel all the way up, THEN drop it down a 1/32 or so. It's got a flat washer at the top that needs clearance. Depending on how much you mortise, they could be dull. You could buy another set and try them just to be sure. The bit and chizzel has to be seated together properly to work good. Just my penny!

[Denny Rice]

Denny: First of all let me say do not spray anything on the bits. Whatever you spray(i.e. water, oil, lubricant, etc.) will drip down and soak into the wood, even if you think you cleaned the outside, its still inside where the bit is. You didn't say what wood you're mortising, but hardwood like oak or walnut is so hard it will cause the bits to get warm or hot. Make sure the bit is all the way in the chuck. Push the chissel all the way up, THEN drop it down a 1/32 or so. It's got a flat washer at the top that needs clearance. Depending on how much you mortise, they could be dull. You could buy another set and try them just to be sure. The bit and chizzel has to be seated together properly to work good. Just my penny!

Rick,

The reason I wondered about a spray of some kind was about a year or so ago I was watching Norm on the NYW and I seen him spray something on his bits before he started the mortising machine. He never said what it was, and as you know all the labels are covered up on the show.

[Rod Sheridan]

Denny, I've used my GI benchtop mortiser for 8 years without problem, almost exclusively in white oak.

You need sharp chisels and auger bits, I guarantee that neither are ready for use in the condition you purchased them in.

The chisels need honing on the outside, as well as inside. Buy the correct sized cone sharpener for the inside, and use a water stone or abrasive on glass to hone the outside.

Buy a small auger bit file and sharpen your bit.

You need enough clearance between the bit and the chisel to allow the chips to clear through the chisel. This happens during the setup, I leave 1/8" gap between the chisel shoulder and the machine, then put the auger bit in and set it so it's touching inside the chisel.

Then I move the chisel all the way up, resulting in a 1/8" clearance between the auger and the chisel. If that's not enough try 3/16".

Once the machine is set up with sharp tools and the proper clearance, it cuts perfectly.......Regards, Rod.

[Paul Ryan]

I second Rod's suggestions. Make sure your bits are smooth as glass and shiny on the outside and sharpen the insides with a cone. The sharpening cones are avaiable from Lee Valley, Rockler, and others. When I put my bits in I use a nickle to space the chisel and the bit. It has always worked for me. They retract smoothly and are very sharp. I cut myself with those things eveytime I use them, it is a given. But they wook really good.

[Rick Dennington]

Denny, I responded on this thread yesterday about cutting mortises. This morning I've been cutting mortises for a hall table in the legs. These are5 ' mortises, and using oak. My bit and chizzel also smoked a little as I was drilling them out. It's no big deal if you get a little smoke, just don't want a lot. I know my bits and chizzels are extremely sharp, but the oak I'm doing is extremely very hard for some reason- seems harded than most I've used. Inside where the oak is glued up in 3 layers is where it's the hardest, and this wood is really dark brown. First I've run across like it, so a little smoke. If you know your bit and chizzels are sharp, and not turning blue, then your ok. I started to throw some water on it---NOT!