The saga of 320 M&T joints

[Dan Hulbert]

Some of you may have seen my earlier posting asking how to clear chips from mortises. Thanks to your feedback, I ended up flipping the board over, tapping out the chips with a dead blow hammer and then finishing the clearing with a shot of compresses air.
I had time over the holidays to work on the mortises. Knowing this was a big job, I ordered a new Premium Hollow Chisel Mortising bit and sharpening cones from Lee Valley. After trimming the bit to length, I stared suing it Christmas Eve. About 20 Mortises into the project, the drill bit broke off in the bottom of a mortise. Had to dig out about 3/8” of the bit. Nuts.
Checked the LV website and saw that their customer service center should still be open. Sure enough, Rob answered and after I explained my problem, he said they would ship me a new bit on Monday and asked that I return the old bit. After I hung up (doh) I thought, Rob at Lee Valley… could it have been Mr. Lee? Who else would work customer service on Christmas Eve?
Back to the shop after Christmas. Had an original Delta bit and put it to work. After sharpening, I managed another 20 mortises and the same thing happened. Drill bit broke, dug it out, started to wonder about my technique. Now I was facing days of shop time without the right tooling. I looked at the broken bit and wondered. If I drill out the mortise, can I use the chisel to square the joint? Then I looked again. If I sharpen the broken drill, would it clear the chips from the chisel? With nothing to lose, I filed the broken end of the drill bit to kind of an auger bit and gave it a test. Not only did it work, but it left smoother sides on my mortises than I was getting with the regular bit! Took a little more effort to plug the end holes, and I tried not to take too big a bite when clearing in between, but it worked!
Even though the new bit arrived from Lee Valley as promised (best customer service anywhere), I continued to use my “broken” bit and finished off the remaining 280 mortises with it.
Granted, I was making ¼” wide blind mortises, 1 ½” deep and 2” long in Poplar, but it worked!
I don’t think this qualifies as a tip or trick of the trade, but if you get stuck, don’t give up.
Now it’s on to final fit all 320 of the tenons. Perhaps I’ll finish by Easter?

[Dewayne Reding]

How many times did you have to touch up the chisel to cut 320 mortises? I have their lower priced chisels (which are decent). Was curious if I should upgrade next time?

[Dan Hulbert]

Twice, but the bit sure could use some attention now. I was close to being done and wouldn't quit to sharpen. A more purednet man would probaly sharpen after 80 mortises or so.

[Jerome Hanby]

[FONT=Calibri][SIZE=3]After I hung up (doh) I thought, Rob at Lee Valley… could it have been Mr. Lee? Who else would work customer service on Christmas Eve?

They have a Rob that works customer service. I caught his name last time I called in and asked if this was Rob Lee. The way Mr Lee posts here it occured to me that answering the phone might be something he would do, but not that time...

[Kirk Poore]

Have you figured out why the bit broke? Granted that 1/4" mortising bits aren't exactly robust, but two in a row is a heck of a coincidence. I've broken chisels before, but only broken one bit.

Kirk

[Chris True]

The bits generally break because they are too high up in the chisel. You need to leave a little space, thickness of a dime is what is usually recommended...

[Kirk Poore]

The bits generally break because they are too high up in the chisel. You need to leave a little space, thickness of a dime is what is usually recommended...

When this happens, the chisel can also be discolored from the heat of friction with the bit. I've had the discoloration, but never broke a bit that way--but I haven't done it to my 1/4" chisel, either. Dan, you might want to check for that discoloration.

Kirk

[Philip Rodriquez]

mmm, should have purchased a Leigh FMT. You would be done in 3 or 4 hours :0) I added a 4" port on mine so I can hook it up to my cyclone.

[Dan Hulbert]

The bits generally break because they are too high up in the chisel. You need to leave a little space, thickness of a dime is what is usually recommended...

I did leave space. More like a nickle's worth. I don't recall any discoloration on the broken bits, but I've already sent the LV back to LV and the broken bit that finished the project has been modified. I'm thinking I may have just been a little too aggressive with my plunging on the first holes, since both bits broke at the same location (bottom of the first plunge).

RE: Leigh FMT. As my wife says, I suffer from male pattern cheapness. $900 to replace a machine that I already have seems more than a little steep. This project may get the Delta hollow chisel mortiser to the point where it doesn't owe me any money, but I haven't paid that much for any machine yet. While I don't have a lot of shop time, I have more shoptime than money.

[Mike Cutler]

Dan

My first project with my Delta Mortiser, 14-651, was much like yours. I had hundreds of M&T joints staring me in the face.
I found that compressed air and a vacuum hose aimed right at the discharge of the waste sped things up, and prevented issues. I affixed the compressed air nozzle and the vac.


Dewayne

I did a lot mortises in Brazillian Cherry, Jatoba, for the project above. I touched up the "stock" chisels and bits nightly, and let the bit cool off. When tthe bit get's hot, it starts to rattle,bind and squeal.