mortising machine

  • Advertise with us

« back to Joinery forum

Forum topic by fis7470 posted 10-27-2014 03:12 PM 1557 views 0 times favorited 5 replies Add to Favorites Watch
View fis7470's profile


2 posts in 1764 days

10-27-2014 03:12 PM

Hello, I have a powermatic mortising machine and I am having problems with setup of the bit. I am try to cut a 3/4 mortise with a 3/4 bit. I inserted the bit and chisel and tighted everything. I extend the bit about1/8 inch past the chisel. I went to cut the mortise and it smokes and burns the wood and doesnt cut the mortise well. I have also had the problem that the chuck falls off the motor shaft. Please let me know any adice or tips for this machine.

5 replies so far

View ChuckC's profile


843 posts in 3390 days

#1 posted 10-27-2014 03:33 PM

3/4” is a large bit/chisel. Is it sharp? I have the PM 701 with PM mortising bits and when I use the 1/2” bit I have to pull down pretty hard on the handle. It’s crucial that the chisels are sharp. If you don’t have a sharpener you should get one. Do the smaller chisels work alright?
Good luck!

View pintodeluxe's profile


5970 posts in 3268 days

#2 posted 10-27-2014 04:26 PM

1+ sharpening cone from Lee Valley or Rockler. Try mortising another piece of wood. Sometimes my 1/2” bit cuts slowly, and I realize there is a hidden knot. Do you have the 719 floor model, or the 701 benchtop?
If it is a benchtop unit, you may have to use a smaller chisel set, and cut the mortise in two passes.

Good luck.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View fis7470's profile


2 posts in 1764 days

#3 posted 10-28-2014 01:25 AM

Thanks for you replies. The model I have is the 719 floor model. I will try sharpening the bit and trying it then. I have a 3/8 bit that works just fine. I just wanted to make sure the machine is capable of a bit this size. I wasn’t sure If the chuck coming loose was a sign of the bit being too large, causing too much vibration.

View HillbillyShooter's profile


5811 posts in 2747 days

#4 posted 10-28-2014 02:07 PM

Here is the link to a good vide on sharpening hollow chisel mortising bits:

Good luck.

-- John C. -- "Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth." George Washington

View bonesbr549's profile


1583 posts in 3522 days

#5 posted 10-28-2014 02:32 PM

I’ve got that same machine, and as others have said, you need to hone those chisels. My first 3/4” chisel, was a little off. I took it back got a different one, and it was much better. I don’t think the tolerances was good on the milling. Get a sharpening cone for mortise chisels and don’t get a cheap one. After you work that put it across your stones to put a good edge on the outside. Finally as a good measure on a large hole like that I hit my bit with wax. You might want to adjust your depth of bit and extend it a hair, and work on your method. I was rough first few, but got the hang of it. Use it all the time without issue. Love it. Sold my domino to help pay for it, and don’t reqret it.!

Only negative I had was I broke the shear pin in the arm mechanism. I went to lowes and got a keyway key and replaced it and no issues since.

-- Sooner or later Liberals run out of other people's money.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics