How to Use a Lock Miter Router Bit

Lock miter bits are used to create an outside miter without the use of a separate spline. The spline is a structural strip of wood concealed in grooves on both sides of the miter. Lock miter bits allow integration of the spline and miter cut without the need for a separate bit to cut the spline. The tongue side of the lock miter implements a ridge (which is cut in a trapezoid shape) to enable the assembled joint to lock together. This bit is designed to cut both the male and female sides of the material without the need to adjust the height of the bit.

Router table
6-inch wide auxiliary rip fence
1 1/4-inch screws
Steel ruler
Push stick
Featherboard
2 12-inch long pieces scrap wood

Instructions

- 1
  Determine the thickness of material to be mitered.
- 2
  Place the bit into the router and tighten it.
- 3
  Place the steel ruler vertically on the surface of the router table and adjust the height of the lock miter bit to the thickness dimension of the material to be cut. For example, if the material is 3/4 inches thick, the bit must be adjusted to the 3/4-inch mark on the ruler.
- 4
  Attach a wood auxiliary rip fence to the side of the rip fence by installing a screw through the auxiliary fence, into the router table fence. Put in one screw at each end of the fence. The rip fence is the cutting guide for the work piece.
- 5
  Adjust the rip fence on the router table to the same dimension as the thickness of the material. This dimension is calculated by measuring horizontally from the auxiliary fence to the outermost part of the bit.
- 6
  Place one of the scrap wood pieces tight against the auxiliary fence and flat on the router table.
- 7
  Turn the router on and place the push stick on the scrap piece, applying downward pressure on the push stick. Push the scrap piece completely through the lock miter bit.
- 8
  Place the second scrap piece with the edge lying on the router table and the side tight against the auxiliary fence.
- 9
  Place the finger board on the router table surface with the finger board touching the side of the scrap piece and clamp the fingerboard to the router table.
- 10
  Make the cut on the second piece of scrap wood.
- 11
  Test fit the scrap pieces together, forming an outside corner.
- 12
  Adjust the height of the router bit if necessary to align the pieces together.
- 13
  Cut the actual work pieces in the same manner as the scrap pieces were cut.

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