# Lock miter for box corners



## generick (May 15, 2012)

I want to build some boxes using a lock miter bit. I have the adjustments done and the corner match is clean and sharp. Here is my problem. I use a router sled to complete the first half of the joint and that works really well. The second piece is pushed through the router bit against the fence and on its edge. I can't seem to keep the 'on edge' piece perfectly straight and flat for the entire cut. It is similar to a cut for the top and bottom of a raised panel door.

Since I'm dealing with the sides of a box, the pieces are much narrower than a cabinet door. What I am looking for a either a better method than push blocks and feather boards or maybe a jig of some type that would make the process easier and safer. A router table sled that works vertically instead of horizontally would seem to be ideal, unfortunately I don't think they exist. A vertical mounted router table would work as well, but those aren't cheap.

Has anyone run into this problem and come up with a solution?

Thanks,
Rick


----------



## builtinbkyn (Oct 29, 2015)

Make a taller fence that can be fastened to your existing fence. That will help stabilize the piece.


----------



## generick (May 15, 2012)

I totally forgot to mention the fence…. I have a taller auxiliary fence installed and that helps with the tilting away from the bit. My primary problem is the stability of the narrow piece. It tends to rock back and forth as I push it across the table and through the bit.

Rick.


----------



## Iamjacob (Mar 18, 2011)

Use a large square piece of plywood as a push block.

The long side against the fence will keep it square and and the long edge against your part will keep your part square.


----------



## Iamjacob (Mar 18, 2011)

Something like this…










with your piece on its face instead of its side.


----------



## generick (May 15, 2012)

Thank you! That's basically what I am looking for. I can make the piece that rides against the face as tall as needed to keep stability.

Rick


----------



## builtinbkyn (Oct 29, 2015)

Ah yes, should have mentioned having a sacrificial piece behind the workpiece to further help stabilize it against a taller fence and prevent tearout. You can also clamp the workpiece to the the sacrificial piece to further eliminate movement. A push block would also help keep it tight to the fence.


> Thank you! That s basically what I am looking for. I can make the piece that rides against the face as tall as needed to keep stability.
> 
> Rick
> 
> - generick


----------



## Jim Jakosh (Nov 24, 2009)

Make a sled that can hold the piece tight to it with a clamp if need be. I do a lot of lock mitering and I have a sled that I clamp my vertical pieces to all the time. It seems impossible to do it with the board floating on its own because you are cutting away the edge that it is riding on. It will want to slide down or in when the miter is cut.

I try to avoid small pieces on either direction. I use a larger board and then cut it to size later if I'm faced with small mitered pieces.

Her is my sled that I use: http://lumberjocks.com/projects/58045

Jim


----------



## generick (May 15, 2012)

All I can say is WOW!. That is amazing. I think you have enough pictures that I can probably try to replicate it. Any word or wisdom or other advice?

Rick


----------

