I use the file to cut the final depth in the linings where brace ends are let in.  I find this method is more precise than using a router or dremel alone, for a clean and accurate slot. This works for both kerfing and solid linings. I’ve made my file to cut to .050” and .070”. But you can cut any depth as deep as the file. Once the desired depth is reached, the file stops cutting.

I start with Stew Mac part number 4556 which is a coarse/medium nut shaping file.  The smallest brace end width I have is .250″.  If your brace ends are smaller then you will need to use a similar smaller file.  This does permanently alter the file but it reasonably priced and for me it has been well worth it in time saved and the final fit.

The other parts and materials needed are two hardwood blocks ( I just used some scraps) approximately 2” x 1”x.25”. About a 6” length of binding, medium superglue and accelerator.

Glue the two blocks to the file spaced out about .5” with the medium glue and accelerator.

To determine the depth of cut, measure the depth of the file, in this case .135”. If I want to make a .070” cut depth I subtract this from the file depth; 0.135”-.070” = .065”. I then thin out 2 strips (one strip for each side) of binding to .065”. I used my widebelt sander but a handplane or scraper will work equally well. This part must be done to the exact measure you want and use a caliper to verify.

Bottom view of file.

Side view of file.

File in use.

To use, I mark the brace locations and remove most of the material with a small router/dremel. I leave it about .005-.010” high. Then I take the file and move it back and forth in the slot just where the depth block is. Once it stops cutting then I’m at the desired depth. The file depth can be adjusted by adding strips of tape to the binding, if needed. If I were to make it again I would use clear Plexiglas so it would be easier to see where I am filing.

Net result.