Hollow Chisel Mortiser Problems

[Marcus Ward]

I've got a delta 14-651 (I think, which ever their latest "pro" model is) hollow chisel mortiser. Today I'm using it to cut through mortises in 3" pine legs for a workbench I'm building. No problem, I cut 4 of them and it goes like buttah. The fifth the bit starts to jam up with globs of pine, not tar, just like.. hardened pine chunks. It stops the motor sometimes. It gets so bad that by the 6th mortise I'm stopping the bit after every plunge and removing it to clean out the pine boogers. What the heck is causing this! It's driving me nuts! I tried waxing the chisel, didn't do much good. Going really slow doesn't seem to help. Maybe resin buildup is causing it? Anyone got any clues because this tool is pert-near useless the way it is right now. This is a new chisel, sufficiently sharp (I saw that because I'm sure someone could use some fancy machine and make it ubersharp), and I'm not doing anything different on the 5th and 6th as I did on 1-4.
Thanks.

[Kirk (KC) Constable]

In my experience, going slow will only make it worse. You don't wanna heat the chisel up anymore than necessary...get it in and get it out. Also, if your workpiece is a bit out of square, it could 'bind' as the chisel tries to pull it away from the fence...which will result in a completely unpleasant mortising experience, and may well have an effect on the clearing of the chips.

[S Larkin]

The bits that Delta includes with the 14-651 are not the best. Try sharpening yours or replace them with better. A three inch through-mortise means removing a lot of wood. You might try drilling out most of the wood with a drill, then squaring up the mortise with the 14-651. Good luck.

[tod evans]

marcus, i ran that same machine for years. try extending the auger another 1/16" and that should help some. if you`re using framing lumber it`s usually wet-n-stringy in the first place but it should still cut the hole....02 tod

[Jim Davenport]

Tod is right. A little extra clearance is in order. I just finished chopping some 1 1/2" mortises in southern yellow pine, using the Craftsman version of your machine. the chips came out "wet and stringy".
Also I clamp mine to prevent movement.

[Byron Trantham]

The bits that Delta includes with the 14-651 are not the best. Try sharpening yours or replace them with better. A three inch through-mortise means removing a lot of wood. You might try drilling out most of the wood with a drill, then squaring up the mortise with the 14-651. Good luck.

I think this is good advice. A 3" deep hole is a lot of material.

[Jim Becker]

And...the softer the wood, the sharper the chisels need to be. If you don't already have them, Lee Valley has some honing stones for your hand-held drill that will keep your chisels keen.

[Marcus Ward]

I am clamping the workpeice to the fence (I thought everyone did that). 3" is a lot of material, I usually do it in 3 plunges, blowing the waste off each time. At 3" the chisel is completely in the mortise and there is no way for the waste to get out which is why I do it in 3 passes. I would say predrilling is in order except it worked fine for the first 4 mortises. I cleaned the bits up with bladesaver and waxed them. I'm going to try sharpening the drill bit tonight, and filing out the corners of the chisel as indicated on the instructions for the honing stones on lee valley's website. I've ordered the honing stones too, we'll see if that helps. Thanks for the advice.

[Mike Cutler]

Marcus.

I have the same machine, and have had the same problems, with brazillian cherry though. These are the things I have done to make the machine work better.

1. I had to augment the holddown with clamps to stop the wood from moving around. I eventually removed the fence and holdown, and now have an XY sliding vise mounted to the mortiser.

2. I have the vacum attachment right at the discharge of the bit/chisel to remove waste as it comes up. I also have an air nozzle pointed right at the discharge of the chisel to help the vacuum.

3. I bought the $6.00 dollar honing cone from Lee Valley, and the diamond sharpening plate.Works great.

4. I don't try to plunge the whole depth in one shot. I progessively go deeper and allow the chips to clear. It takes about a week to get a new handle from Delta if you break the Mortiser handle. Damhikt.

5. I honed the leading edge of the auger bit.

Of all the wood to work with, pine is my least favorite. It really gums up machines. I'll never rip a 2x4 through a bandsaw again. What a mess

[Marcus Ward]

Okay I am good on #'s 1,2,4... I will try 3 and 5 as soon as I can. Yeah I'm not a fan of pine either, I have tried to avoid running it through any of my machines but this project kind of ended up with it. A friend of mine gave me an older craftsman 12" bandsaw (tilting head, big table) and asked me to build him a 24x48 workbench. I built the top 2" thick from white oak but the legs and stretchers are from pine. I should have used oak for them too, I guess. Having to clean all my blades afterward makes it not worth it.