Shop-Made Miter Clamps

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Liliana Harvey
5 years ago
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*Editor s note: In the photos showing the table saw, the blade guard has been removed for clarity. I try to be as self-sufficient as possible, so I like to manufacture my own tools whenever I can.

For one clamp, you need a hardwood plywood scrap, a piece of 3/4 aluminum T-track, a 1/4 T-bolt, a star knob, a fender washer and a few screws. High-friction grip pads are optional.

Milling the Base After ensuring that your saw blade is perfectly perpendicular to the table saw top, cut the plywood into rectangular bases (according to the number of clamps you require), about 12

1 *Editor s note: In the photos showing the table saw, the blade guard has been removed for clarity. I try to be as self-sufficient as possible, so I like to manufacture my own tools whenever I can. I designed miter clamps that are simple to fabricate and require only scrap plywood and readily available hardware. For one clamp, you need a hardwood plywood scrap, a piece of 3/4 aluminum T-track, a 1/4 T-bolt, a star knob, a fender washer and a few screws. High-friction grip pads are optional. I suggest you use good quality 18mm (about 3/4 ) thick Baltic birch plywood. This material is strong, smooth, and stable. It has very few voids and a nice, plain grain. Milling the Base After ensuring that your saw blade is perfectly perpendicular to the table saw top, cut the plywood into rectangular bases (according to the number of clamps you require), about 12 long x 10 wide each. Ensure that all four corners of each base are square. Measure your aluminum T-track (width and depth) precisely and mill dadoes lengthwise through the centers of the bases. The T-track should fit snugly in the dado and be just shy of the top face, as shown. Using such a track will prevent any glue from sticking to your clamps and will allow the clamping assembly to ride smoothly. The next step is to set your miter gauge at a precise 45 angle. A quick and effective method to do so is to place a framing square on the table saw, keeping the long side against the miter gauge. Pivot the miter gauge until the two inner 10 (or 12 ) marks are in line with the same side of the miter gauge slot of the table saw (see arrows). Tighten the miter gauge to lock in a perfect 45 angle. 1/5

Before going any further, check if the face of your miter gauge is too slick.

You must make sure that the cut will exactly kiss the outside corners of the dado.

When both cuts are done, you should have a perfect combined 90 angle.

Milling the Jaws To cut the two remaining corners, you can use the rip fence.

dado. If the corners are square, you won t have to move the rip fence for the second cut.

2 Before going any further, check if the face of your miter gauge is too slick. If it is, stick a strip of fine-grit sandpaper to it to prevent any creeping. When ready, clip the corners off. You must make sure that the cut will exactly kiss the outside corners of the dado. You may have to walk around your table saw to set the cut-line precisely. When both cuts are done, you should have a perfect combined 90 angle. Check it with a framing square, as shown; achieving this angle is critical to the project s success. Milling the Jaws To cut the two remaining corners, you can use the rip fence. Once again, take your time when aligning the fence so that the saw blade will cut from the tip of the outside walls of the dado. If the corners are square, you won t have to move the rip fence for the second cut. For each clamp you re making, nail and clamp together two of the corner cut-offs, ensuring each side of the 90 corners are flush. These pieces will be part of your clamping assembly jaws. To make additional jaws, either fixed or stationary, for your clamps, rip a strip of your plywood the same width as the combined base and stacked 90 clamp jaw. This should be 54mm, or approximately 2-1/4. 2/4

For each clamp, two pairs of jaws are required. On one pair, cut both ends of each piece at 45 ; on the other pair, cut one end of each piece at 45 and the other end square, as shown.

On the bottom jaws, one of each of the 45 jaw ends is in line with the edge of the base side, while the other is 3/4 away from the corner of the dado.

After gluing and nailing the jaws to the base edges, cut the aluminum T-track to length using a hacksaw. After this is done, drill and countersink holes in the T-tracks, if required.

3 For each clamp, two pairs of jaws are required. On one pair, cut both ends of each piece at 45 ; on the other pair, cut one end of each piece at 45 and the other end square, as shown. Note the positioning of each jaw in the photo. On the bottom jaws, one of each of the 45 jaw ends is in line with the edge of the base side, while the other is 3/4 away from the corner of the dado. On the upper jaws, the 45 jaw ends are aligned with the walls of the dados, while the square ends are about 3-1/2 away from the backs of the adjacent lower jaws. After gluing and nailing the jaws to the base edges, cut the aluminum T-track to length using a hacksaw. After this is done, drill and countersink holes in the T-tracks, if required. Keep in mind that upward force will be applied in use. If your dadoes are tight, I suggest you use a plywood scrap and a hammer to drive the T-tracks down into the dadoes. This will ensure slick tracks for the sliding jaws to ride in. Use appropriate-sized wood screws to secure the T-tracks to the bases so that the sliding jaws won t catch on the screw heads. 3/5

Place the sliding jaw tightly into the upper corner of the base as shown and make a pencil mark at the lower edge of the

Transfer the center point onto the top of the jaw.

Repeat the process for each of your sliding jaws.

a shop-made or store-bought star knob with a good grip. Your clamps are ready for use now, but you can go a step further.

4 Place the sliding jaw tightly into the upper corner of the base as shown and make a pencil mark at the lower edge of the back of the jaw dead center in line with the center of the T-track (see arrow). Transfer the center point onto the top of the jaw. Next use a center punch and a hammer to make a dent and then use a drill press to drill a 1/4 through hole. Repeat the process for each of your sliding jaws. The Assembly After sliding a T-bolt into the aluminum T-track, place the jaw onto the T-bolt and add a fender washer and a shop-made or store-bought star knob with a good grip. Your clamps are ready for use now, but you can go a step further. You will get a better grip to secure the mitered pieces to be clamped if you add pieces of high-friction grip mat to two faces of your sliding jaws. Another option is to use strips of fine-grit sandpaper. If you use Baltic birch plywood, the edges are not too slick so this step is optional. 4/5

This photo shows a typical miter joint that has been glued. Since the glued joint sits just beyond the aluminum track, glue squeeze-out is not a problem.

It shows why the location of the fixed outside jaws is so important.

One other option is to make the U-shaped bridge shown. This will enable you to use a bar clamp to apply more pressure if required until the star knob has been tightened.

You may be tempted to add sandpaper or grip mats to the inside walls of the outer jaws, but I think they would interfere with adjusting the mitered pieces to be joined.

5 This photo shows a typical miter joint that has been glued. Since the glued joint sits just beyond the aluminum track, glue squeeze-out is not a problem. The joint can be left in the clamp while the glue dries or it can be nailed while in the clamp and then removed. Shown here is a frame miter joint that has been glued using the other end of the clamp. It shows why the location of the fixed outside jaws is so important. Using this particular miter clamp, I can glue frames up to 3-1/2 wide and, once again, leave the clamp alone while the glue dries or nail it while temporarily secured. One other option is to make the U-shaped bridge shown. This will enable you to use a bar clamp to apply more pressure if required until the star knob has been tightened. After removing it, you ll be able to nail your joint, if necessary. Here are two shop-made miter clamps ready for use. You may be tempted to add sandpaper or grip mats to the inside walls of the outer jaws, but I think they would interfere with adjusting the mitered pieces to be joined. I found this project to be very satisfying. I hope you get as much satisfaction as I did if you make a few to use in your shop. Happy woodworking! Text and photos by Serge Duclos Serge Duclos started woodworking 40 years ago after purchasing a house. He soon found it was a way to relax from the stress related to his job as a human resources professional. Since retiring in 2004, Serge continues to enjoy his pastime and to update his bilingual woodworking blog with his projects, as well as his tips and techniques. 5/5

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