Using the Lock Miter Router Bit
compiled by Loren Hutchinson

The Jesada Lock Miter and Lock Miter Jr. router bits have been the subject of many posts on the forum. This article represents the compilation of the best advice found on the forum regarding how to set up and use these bits. Be sure to read all the way to the last posting which is from Cliff Paddock of Jesada Tools.

Posted by: Eric Laliberte on August 13, 1998

A lock miter bit works using the principle of equalateral triangles. In other words, you want to set the bit up so that the height above table top and distance in front of the fence equal the thickness of the workpiece. The easiest way I know to do this is to make a jig out of some thin stock, 1/4" or thinner. Make a cut out that is the same height as your workpiece thickness and long enough to fit around the maximum diameter of the bit. Then move the bit vertically and the fence horizontally until the jig just touches the carbide. You should be very close at this point. A sample cut or two and you be should be there. Take your time setting up the first time. When everything is perfect run a scrap piece. This will be your set up gauge the next time you run the same thickness.

Posted by: Tony Brown on August 13, 1998

Try this. Mark the center of your stock's thickness, then raise the bit until you have that channel that runs around the bit roughly centered. (now the fun part) On the 2 sides of that channel you will see that 1 wall of the channel is angled and one is perpendicular (straight) to the shaft of the bit. You want to line up the perpendicular wall with the centerline of your stock, then move your fence so you only take light cuts.

Posted by: LOU V.K. on November 12, 1997

Due to a relief grind being needed on any single bevel cutting tool,the profile is changed when the cutting face area is reduced.In as a lock miter bit is designed to make cuts in two pieces of lumber,which must then mesh,the reduction in face area will produce cuts which will not match in profile.I also have a lock miter junior bit from Carlo,which I like very much,but use it most judiciously,as I am aware that it is not resharpenable.This is a very expensive bit,which performs flawlesly,thus I will never use it on plywood,as the glues in plywood will dull it quite quickly.

Posted by: Paul Jordan on January 21, 1998

With 3/8" [thick stock] I'd make sure you have a table mounted featherboard holding the stock into the fence. Make sure your fence is dead nuts flat. I also cut a zero-clearance fence insert just for this bit. I have setup pieces saved for each stock thickness I've used, but of course you have to have one good setup to get those blocks (make one vertical setup block and one horizontal when you finally get it dialed in). Does your router have a micro-adjust? If so, eyeballing it at first and then trial and error should get you there in 10 minutes or less.

Posted by: Bill H. on January 26, 1998

I used the lock miter jr. on a set of six drawers.I had many of the same set up troubles as you describe. My solution was to get the bit set close and then "pre cut" the miter on the table saw. Set the blade at a 45* and trim off most of the excess, effectivly rough cutting the miter befor running it past the router bit. It still took some time but the end result was well worth the effort. One last thing,make sure all your stock is planed at the same time. Any difference in thickness will make you nuts!

Posted by: Paul Jordan on January 07, 1998

Awhile back I posted a review on the Jesada Lock Mitre Jr. router bit. That review was done after the initial use and some perfunctory test cuts.

I've now had the opportunity to use it a fair amount and in the process have created the necessary setup blocks (one for height and one for depth of cut, for each stock thickness) in order to make repeat settings. Amazingly, this setup method works without a hitch, although I need to put a piece of white paper behind the bit so I can eyeball the setup piece and bit at the same time.

Posted by: Jesada Tools, Cliff Paddock on November 25, 1997

Carlo Venditto asked that I respond to your questions and concerns regarding the Lock Miter Junior Bit.

The instructions for the Lock Miter Junior are available online at our web site, Once you get to the site click the Shop tips button, then the Router Bits button, then select Lock Miter. [There is also an instruction booklet available from Jesada. Call their toll-free number at the bottom of this article. -Loren]

The bit does require test cuts to set up, but you can simplify the process by concentrating on the height of the bit first. The fence location isn't critical until you make the final pass. To center the bit in the workpiece, make test cuts with the workpiece flat on the table. When the bit is properly centered the "shoulders" of wood above and below the "teeth" of the bit will be of equal height. I realize that my terminology may not seem very precise, this is a case where it would be much easier to explain the process if you were looking at the instructions. Please note that although the fence location isn't critical for these test cuts, safety requires that you have a fence in an approximately correct position for the test cuts. Once you have the bit height correct you can make your first real pass. I usually make cuts in 3/4" material in two passes. Set the fence so the bit miters about half the stock thickness. Make your horizontal and vertical cuts. Now set the fence for the final cut. This is best achieved by working with the horizontal piece first, adjusting the fence outward until the bit just cuts a complete miter.

Please be sure to use hold-downs, hold-ins and pusher blocks with all of these steps, and be sure to refer to either the online instructions or the instruction book, as I have given only a summary of the steps.

I hope you'll contact me by email ([email protected]) or phone (1-800-531-5559) if I can be of any help. Sorry if any of the above is unclear, but I was trying (not too successfully) to be brief.

Cliff Paddock, Jesada Tools


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