How to Make Self-clamping 90° corner clamps

If you have seen one or more types of right-angle corner clamps for woodworking, you will notice that they all have one thing in common.

They need clamps!!!

For each woodworking corner clamp, you need at least 2 clamps.
But clamps are expensive, so that could be the reason you don’t own that many of them, just like me.

With the self-clamping DIY corner clamp, you’ll discover in this article, clamps will be no longer needed.

Learn how you can make these cabinet-making jigs for your woodworking workshop.
You will discover how thanks to the included video and step-by-step instructions.

So, let me show you how I built it.

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What are corner clamps used for?

If you want to connect two boards at an angle of 90 degrees, this can be difficult.
You need both hands to hold the boards in the right position, and at the same time, you also have to screw.
So you are short of hands.
This problem can be solved with a corner clamp.

If you want to connect two boards at an angle of 90 degrees, the corner clamp needs to be placed on top of the connection.
That way, the corner clamp keeps the boards perfectly in place.
Meanwhile, you can screw without the planks shifting.
Handy, isn’t it?

How many corner clamps do I need?

The best answer to the question of how many corner clamps you need is 4 pieces. I explain why.

Corner clamps will be mainly used in cabinet making.
Because there are 4 corners on a cabinet, you need at least 4 corner clamps.
This way you can clamp each corner of the cabinet at right angles, and be sure that the connections are correct when you start screwing.
After screwing, these clamps can be loosened, and you can use them to make the next cabinet.

That is why a minimum of 4 corner clamps is the most ideal number to have in your workshop.

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Watch the video & see how to make a corner clamp

If you want to see how I build my self clamping corner clamps, you can watch the video below.

After watching this video, you can go on reading this blog to make your own self clamping corner clamps.

How to make self clamping corner clamps?

With these step-by-step instructions below, you can build your cabinet clamps easily.

Step 1 | Preparation

All the wood I used to make this corner clamp is 18 mm birch plywood.
I used all pieces of scraps from previous projects.
I want to encourage you to save all your pieces of scrap wood from now on.
You can always use them to make smaller projects, like this one.

To start making this corner clamp, I first made the top part of the jig.
This is a triangle that will ensure that the corner you want to connect, when using this corner clamp, is square.
Make sure that this part makes a perfect angle of 90 degrees.

This part will later be connected to the lower part with a bolt.
On the spot where the bolt should be, I drilled a hole with a 14 mm Forstner bit to a depth equal to the thickness of the bolt’s head.
This way, the head of the bolt will be flush with the top of the wood.
In the center of the 14 mm hole, I drilled a hole that goes all the way through the wood with an 8 mm pointed drill bit.

Self-clamping 90° corner clamps

After sanding this part, I placed it in position on a piece of wood from which I cut the bottom of the corner clamp.
For that, I placed two pieces of scrap wood on the edges of the wood. This gave me a reference, to where the triangular part would go when the corner clamp is in a closed position.

Once that position could be determined, I was able to mark the start of the slot through the hole of the triangular part.

The slot, in the bottom of the corner clamp, will allow the triangular part to move easily forwards or backward.
You will find out more about that later in this article.

Self-clamping 90° corner clamps

Once I had established that point, I also marked all other dimensions to make the corner clamp’s bottom part.

Self-clamping 90° corner clamps

Step 2 | Making a slot

As mentioned earlier in this article, I made a slot in the lower part of the corner clamp in which the bolt can move up and down.
The bolt I used has a diameter of 8 mm (M8x60mm).

To make the slot, I chose to use a router bit of 10 mm, which ensures that the bolt can move easily.

When making a slot in birch plywood with a router, do it in several steps.
Birchwood tends to burn quickly.
So if you try to remove a lot of wood at once, there is a good chance that burn marks will remain on the wood.

If you do have these burn marks, you can try to remove them with coarse sandpaper.

Self-clamping 90° corner clamps

Step 3 | Cutting to size

Ok, now it was time to cut out the shape of the bottom part of the corner clamp.
To make the round shape where the jig merges into the handle, I first drilled two holes with the largest Forstner bit I have in my workshop (40 mm).
Then I could start cutting this part.
I tried to cut as much as possible with the crosscut sled, but that was a wrong idea.
I should have cut everything by hand instead.

Due to the round shape of the saw blade, the blade cut out the bottom just a little further, and at one point I cut into the bottom of this part.
If you watch the video closely, you will definitely see that small error.
I immediately reinforced it by filling this small saw mark with epoxy glue.
The pieces that were not cut through were finished with the Japanese handsaw.

Self-clamping 90° corner clamps

Step 4 | Assembling

Once I had cut out all the pieces and sanded the edges, I could start assembling.
First, I attached the clamping blocks to the bottom plate.
I did that by gluing them to the base with wood glue and then reinforcing them with a brad nail.
If you’ve been following me for a while, you know that this is a favorite way of working for me.
The brad nail keeps everything in place while the wood glue dries.
That way I can immediately continue working and not lose any time.

Self-clamping 90° corner clamps

After placing the M8 bolt through the triangular part and the slot, as well as the hexagon bolt on the top of the jig (at the bottom), the two could be connected together.
For this, I used an ordinary rubber band, something that everyone has at home.
I made three turns in the rubber band, but you can of course give more turns if you want the corner clamp to tighten more.
After placing the rubber band under the washer that was over the hexagon bolt, I tightened this bolt so that the rubber band remains firmly in place.

Self-clamping 90° corner clamps

Where the rubber band is over the M8 bolt, I placed it between two washers.
This way, the rubber band will not prevent the jig from opening or closing.
By placing a washer under the rubber band, it will slide through the slot as if by itself.
To close the two washers, I used two nuts.

Pay attention!
Do not over tighten these nuts against the washers or the jig will have a hard time working.
Tighten the nut slightly so that everything stays together, but the jig can move up and down smoothly.
Once you have determined that point, tighten the second nut against the other nut.
With two wrenches, you can then turn the nuts against each other (turn the bottom nut to the right and the top nut to the left).

Self-clamping 90° corner clamps

Step 5 | Improvements

After a first test, I noticed that the corner clamp worked as I had hoped, but handling the jig was rather difficult.
So I made some minor adjustments.
In the triangular part, I drilled two 18 mm holes with a Forstner drill.
At the bottom of the handle, I made a small indentation with my drum sander.
These holes are just a bit bigger than my fingers.
So I now have a better grip on the corner clamp, and because of this, I can now operate the jig with one hand.

How to use these Corner clamps

It shows itself how to use this corner clamp.
Place your fingers in the holes provided, and pull the jig open until it fits over the material you want to clamp.
Place the corner clamp over the wood and let the jig contract itself by releasing it.
Check whether the connection you want to make fits properly and start screwing, nailing, or whatever you want to do to connect those pieces.

Self-clamping 90° corner clamps

Because you have read this article, chances are that you are very interested in making clamps.
In the past, I built a few other clamps that you should definitely check out.
You can inspire yourself on these blogs:

Don’t forget to download the cabinet clamp plans for this clip at the bottom of this article, before moving on to these other blogs.

Check out my article — What woodworking clamps do I need? — if you want to know what woodworking clamps you should have as a bare minimum in your workshop. 
In this post, I’ll teach you how to determine which clamps are most important for your workshop, so you may buy only what you absolutely need.

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