How to Make a Jig for a Box Finger Router Bit

Written by jim wildman
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A box finger joint is an interlocking joint with fingers that joins two pieces of wood at a right angle. It is made with a carbide tipped router bit, a router table and a fence. A custom-made jig will save you time and increases the precision of your box finger joints. The box finger joint router bit comes in a 1/4-inch and a 1/2-inch shaft size and is intended for use in a router table only.

Skill level:
Moderately Easy

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Things you need

  • Safety glasses and hearing protection
  • Straight edge
  • Router table with fence
  • Box finger joint router bit
  • Table saw
  • 1/4-inch Birch plywood
  • 3/4-inch wood scrap
  • Framing square
  • Tape measure
  • Metal ruler (optional)

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    Box Finger Joint Router Bit Setup

  1. 1

    Start by putting on your safety gear.

  2. 2

    Unplug the router at the router table.

  3. 3

    Move the router fence out of your way.

  4. 4

    Install the box finger joint bit into the router.

  5. 5

    Adjust the router table's fence so the outside edge of the router fence is in line with the outside edge of the router bit's guide bearing. Lay a straight edge against the fence and adjust until the guide bearing just touches the straight edge. A metal ruler works great for this.

    Box Finger Joint Jig

  1. 1

    Use a table saw to cut a piece of 1/4-inch Birch plywood into a rectangle that is 6 inches wide by 9 inches long.

  2. 2

    Continue using the table saw and cut 2 pieces of 3/4-inch scrap wood into blocks that are 2 1/2 inches by 6 inches long.

  3. 3

    Use a pencil and a square to mark a line that is square to the plywood 1 1/2 inches in from each end of the plywood.

  4. 4

    Use glue and screws to attach the 3/4-inch blocks to the plywood along the inside of the pencil lines that you made.

  5. 5

    Take the jig you just made and set the long side next to the fence. Adjust the box finger joint router bit in the router table so that the bottom edge of the cutter is just touching the top of the 1/4-inch plywood of your jig. Turn on the router and run the jig through the router, cutting only one of the 3/4-inch blocks of your jig. Mark the block that you just cut "A."

  6. 6

    Adjust the box finger joint router bit so that it raises up the height of 1 tooth. Use the jig as a reference for this adjustment. Now rotate the jig 180 degrees so that the opposite side is against the fence and run it through the router bit. Again, just cut the one 3/4-inch block and mark it "B." You just completed the box finger joint router jig.

Tips and warnings

  • Wax the jig and router table and fence with a nonsilicon paste wax. This will make it a lot easier to use the jig.
  • Use the jig you made as a set-up jig for adjusting the height of the box finger joint router bit for future use.
  • Only use this router bit with a router table.
  • Always unplug your router when changing bits or making adjustments.
  • Never use a router bit that is dull or damaged.

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