Locking Mitre Bit - First Time

[Dwain Lambrigger]

I am using a locking mitre bit wiith a 1/2" shaft on my table for the first time tomorrow. I was making a set of oak boxes for my wife. I was wondering with the best router speed was for this bit. I plan on testing the bit several times, as I want to make sure this works right, but I was wondering if anyone else out there has experience with this type of bit.

Thanks, and have a great holiday!

[glenn bradley]

That style of bit comes in different diameters. Larger diameters have more speed at the outer edge for the same profile. I generally run bits up to about an inch at full speed. I slow way down to 9 or 10k rpm for 3+ inch raised panel bits. I would guess you'll end up happy somewhere in between. I believe Milwaukee has speed charts on their web site which could help.

[Bill Huber]

This is a speed chart that is around the net that is kind of a standard.
Your router should have a table of some type in the manual with the speeds and or numbers that are on your router.

I generally run just a little slower then this chart shows.


1” (25mm) 24,000 RPM
1-1/4” - 2” (30-50mm) 18,000 RPM
2-1/4” - 2-1/2” (55-65mm) 16,000 RPM
3” - 3-1/2” (75-90mm) 12,000 RPM

[Michael Weber]

Dwain, good luck with that lock miter bit. I suspect that getting the speed right will be the least of your problems. These bits are notoriously difficult to set up correctly so have a LOT of extra stock of the EXACT same thickness of your box material. Be prepared to spend a LOT of time adjusting your fence and depth of cut. I used one once and unless I had to make an almost production quantity run of like material I don't think I would opt to ever use it again. You may know all the above already in which case I apologize for being redundant.

[scott spencer]

Dwain, good luck with that lock miter bit. I suspect that getting the speed right will be the least of your problems. These bits are notoriously difficult to set up correctly so have a LOT of extra stock of the EXACT same thickness of your box material. Be prepared to spend a LOT of time adjusting your fence and depth of cut. I used one once and unless I had to make an almost production quantity run of like material I don't think I would opt to ever use it again. You may know all the above already in which case I apologize for being redundant.

Hi Dwaine - Just wanted to second Michael's comments about get the setup correct. Tough bits to dial in, but once you get it right, progress on the actual work piece should go well. I think it took 3 or 4 tries my first time, so it's not an awful experience, but isn't likely to come in one or two tries either. My bit is a fairly large Holbren that I slowed down a fair amount. Depending on your router, but may have to make a couple of passes.

Good luck!

[David DeCristoforo]

"These bits are notoriously difficult to set up correctly..."

Try this. These instructions were written for the shaper but will work just as well on a RT....

Plane a couple of extra pieces to the same thickness as the material you are using for your project. Put an "X" on one side of each piece. Start by running the pieces horizontally thru your cutter, one piece "X" down and the other "X" up ( keep track of which piece was up and which was down), slide the two pieces together and see if the outer surfaces meet up, adjust your cutter vertically until the surfaces match exactly.

Now run your pieces vertically against the shaper fence, one with the "X" towards the fence, and one with the "X" away from the fence, again keeping track of which is which. Adjust your shaper fence in or out accordingly to make the outer surfaces match up exactly. Now you are set, chop the ends off of your test pieces, run one piece level and one piece upright against the shaper fence and verify your fit. Then you can run you project. You might want to keep the pieces as setup gages when you run some material of the same thickness again.

A modification to this procedure: Instead of using stock exactly the same thickness as your project material, use material surfaced 1/16" thinner. This will cause the machine, once set up to leave a small flat on the edge of the project (not the set up) board, instead of leaving it totally knife edged. The knife edge tends to get damaged as it runs against the fence, after the lockmiter has cut it. Remember that you will need to re-surface (sand or plane) the finished product to remove the flats, so make it oversize accordingly.

[John Lucas]

The locking miter bit can be rather easily setup if you simplify the task. I set up one variable at a time. Try this:
http://www.woodshopdemos.com/cmt-lm10.htm

I set the height first using two boards run flat on the table.
http://www.woodshopdemos.com/cmt-lma9.jpg

Then adjust for the depth of cut (vertical):
http://www.woodshopdemos.com/cmt-lma10.jpg

This is a real good joint once you have setting up down pat.

[glenn bradley]

I was just about to post that one of our fine members, John Lucas has a great demo on this. Thanks John, for beating me to it.