Making Clamping Squares From 3/4” OSB

Looking for an inexpensive set of clamping squares? Same here, and what follows is what I came up with.

Topics Covered
1. Build Sequence
2. Finish
3. Clamping Square Usage
4. In Closing
5. Request

1. Build Sequence
Using your table saw cut four pieces of 3/4” OSB to the following dimensions: 3/4” x 3” x 12”. The four OSB boards shown in Photo 1 will not be the final dimensions, just the dimensions you will start with.

Photo 1

Now, square up and brad nail two pieces of OSB together as shown in Photo 2. Angle your brad nailer slightly toward the interior of the OSB, to hopefully avoid any brads blowing out the sides of the OSB.

Regarding the brad nails, use 18-ga. x 1-1/4”-length brads for all brad nails referenced in this post.

Photo 2

The two OSB boards in Photo 2 are labeled as “1” and “2.”

For fastening the two OSB boards in Photo 2 where they overlap, use brads in a 3 x 3 nailing pattern plus four additional brads for a total of 13 nails, and spaced approximately as shown in Sketch 1.

Sketch 1

Regarding the dimensioning shown in Sketches 1, 2, & 3–I just approximated the dimensions shown by eye for shooting the brads shown.

Next, square up and brad nail the third piece of OSB, which is labeled as “3” in Photo 3 and as “Board 3” in Sketch 2, to OSB board “2.”

Photo 3


And then, square up and brad nail OSB boards “1” and “4” together. These two OSB boards are shown and labeled in Photo 4 and also Sketch 3.

Photo 4


Using a table saw and a sled to remove any possible unevenness on the two outside sides of the square is ideal. With the setup shown in Photo 5, remove 3/16” from each of the two outside sides of the clamping square. This reduces the width of each leg (of the clamping square) from 3” to 2-13/16”.

Photo 5

Next, trim the two legs to desired length, which is easily done using the sled shown above in Photo 5. A shot of one of the two legs being trimmed to desired length is shown below in Photo 6.

Photo 6

Shown on Sketch 4 are the final dimensions for the clamping square after trimming the outside sides and ends of the four OSB boards.


After square has been trimmed and cut to length, ensure that the brad nailing patterns shown in Sketches 1, 2, & 3 are applied to both sides of the clamping square.

Wrap up the build of this square by using a disc sander to notch the corner where the two legs intersect. This notch is shown in Sketch 4 along with associated 3/8” dimensions. Plus, Photo 7 below shows a more complete view of the notch.

Purpose of the notch is to prevent glue squeeze-out from making contact with the clamping square, if glue is being used on boards being clamped by the clamping square/s.

2. Finish
For finishing, start by sanding the clamping square faces with a random orbital sander using 120-grit sandpaper. It is amazing the improvement sanding makes on the appearance of the clamping square faces. Photo 7 shows the clamping square after having been sanded.

Photo 7

After sanding the clamping square, apply a finish. (I applied one coat of one part poly to one part paint thinner with a brush.)

The clamping square is shown below in Photo 8 after having applied the polyurethane and paint thinner mixture referenced above.

Photo 8

3. Clamping Square Usage
Photo 9 below shows the clamping squares being used to square up the exterior boards of a box.

Photo 9

4. In Closing
So if you’re in need of a clamping square/s, build a couple out of OSB as described above. I believe you will find them to be a handy addition for use in your shop. And they are relatively inexpensive and easy to build.

The 1-1/2”-wide surface is advantageous for clamping the clamping square to whatever it is that you want to square up. Plus, the wide surface makes for a more stable clamping square when resting on a horizontal surface.

And just for the record, there is nothing sacred about the dimensions given here for building the clamping square. Builder’s prerogative applies regarding the clamping square dimensions. I have already made several smaller clamping squares to accommodate clamping and squaring up smaller boxes.

5. Request
If you enjoyed this post, I would be very grateful if you would share it by email with a friend, on Google+, and/or Facebook. While I am being needy, would you give me a “Like” on my Facebook page (Woodworking with AJO)? You can click on the link shown below for my Facebook page. Thanks a bunch.

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Take care