How to Build a Tapering Jig

Cut 2 Pieces of Wood

First, measure and cut two identical pieces of wood that will form the two sides of the tapering jig. The standard length for each board is 30 inches. But you can adjust the length if you want a shorter or longer jig for a specific project. Just make sure both boards are the same length.

Attach the Hinge

Stack your two cut boards on top of one another. Then, attach the hinge to one end of the boards. Make sure the hinge is parallel with the boards and centered right in the middle of the two of them.

Drill Holes for the Carriage Bolts

Drill a hole through the top of each side board on the opposite end from the hinge as shown in the image below. The holes should be an inch up each sideboard and be just large enough for the 1/4-inch diameter carriage bolts to pass through snugly.​ Next, drill a hole through the bottoms of each side board. Be sure the holes are deep enough that the heads of the carriage bolts won't protrude from the bottom of the jig.

Insert the Bolts

Insert the carriage bolts through the holes, and tap them into place. Verify that the heads of the bolts are lower than the surface of the wood.

Build the Spreader Bracket

The tapering jig is held at the appropriate angle with a spreader bracket. To begin building this spreader bracket, cut a piece of wood to 2 inches wide by 8 inches long. Round the edges with your jigsaw as shown in the image below.

Next, draw a pencil line down the long axis of the board at the center line, which should be 1 inch from each side. Then, using your drill, make three 1/4-inch diameter holes: one hole at 1/2 inch in from each edge on the center line and the third hole at 1 inch in from one edge also on the center line.

Cut a Slot in the Spreader Bracket

Using a pencil and ruler, draw a line from the top edge of the center hole in the spreader bracket to the top edge of the hole farthest away (on the opposite edge of the bracket). Then, draw a parallel line between the bottom edges of these two holes.

Then, using your jigsaw, cut along these two lines to create the slot in the tapering jig spreader bracket.​

Attach the Lip

Cut a 2-inch wide piece of wood. Using your drill and a couple of deck screws, attach this piece to the left side of the jig up 1 inch from the end of the board. This piece can be positioned flat or butted against the left edge (as shown in the image below). This lip is what will actually push the board being tapered through the saw blade.

Attach the Bracket

To complete the assembly of the tapering jig, attach the spreader bracket to the jig.

Position the slot of the spreader bracket over the left carriage bolt and the hole over the right carriage bolt. Tap the bracket down into place. Next, add a flat washer and lock bolt onto the right carriage bolt. Tighten until the bracket is snug but not so tight that it won't rotate on the bolt.

You should now be able to move the left bolt through the slot, widening and narrowing the tapering jig. If satisfied with the freedom of movement of the jig, attach a flat washer onto the left carriage bolt, followed by a lock washer and then a wing nut to secure.

Use Your Tapering Jig

To use your tapering jig, adjust the angle of the jig and tighten the wing nut. Position the board to be tapered firmly against the left side of the jig, with the end of the board against the lip at the bottom end of the jig (as shown in the image below).

Next, place the right side of the jig against your table saw fence. Adjust the position of your fence, so you're cutting the taper at the desired width.

Hold the board against the jig and the jig against the fence. Slide the entire apparatus through your saw blade. You should end up with a consistent, cleanly tapered board.