Some time ago I published an article on the best DIY Right angle clamp. It is certainly a great workshop tool so much needed for a lot of woodworking projects. Whether building cabinets, shelves, or furniture the angle clamp is a must.
This time I made a slightly different type of corner clamp. The DIY corner clamp (clamping square) is used when assembling two pieces of wood accurately at 90 degrees. In addition, they are also useful when joining 2 pieces of wood of different thicknesses or when joining pieces of wood where there is little space for handling.
The corner clamp can be used with all types of edges – beveled edges or fragile cutting edges. They are very easy to assemble and they maintain a perfect right angle while joining 2 pieces of wood.
The body contains a routed slot on each side of the square that provides a sufficient area for clamping. The inner side of the clamp is also flattened offering additional space for clamping including a drilled hole in the center that can be used for joining mitered corners.
There are all sorts of different types of clamping squares available on the market but they get quite expensive. With a little care, you can make similar ones at a minimal price.
In this article, I will walk you through step by step how to build these DIY corner clamps / DIY clamping squares. You can find the plans below.
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Table of Contents
- The material you will need
- Free DIY Corner Clamp Plans
- General Questions
- How difficult it is to make a corner clamp?
- How do you use clamping squares?
- Are corner clamps worth it?
- What can I use as an alternative to corner clamps?
- How to Make a Corner Clamp
- Cut the wood pieces
- Ensure the squareness of the clamp
- Cut the shape of the clamp
- Draw the design and cut the inner parts
- Cut the clamping slots
- How to use a corner clamp
- How to clamp a miter joint using a corner clamping jig
- DIY Corner Clamp Video
- Woodworking Jigs Used
*Safety is your responsibility. Make sure you know what you’re doing and take all necessary safety precautions while working with power tools. Safety comes first!
The main power tool I am using for this project is a circular saw. Go and check these safety precautions if you haven’t already.
What you'll need to make the
corner clamps/corner squares
Corner Clamps – material:
1x Plywood desk (16 x 40 x 1,2 cm)
Router bit – ø6mm Straight Router Bit
Forstner bit – 30mm
Double-sided “carpet” tape
Sandpaper (200 grit)
How difficult is it to make a corner clamp?
The difficulty of making a corner clamp depends on several factors. First, the tools that will be used for the job, and second, the amount of work invested to achieve an accurate and precise right angle. However, even with basic tools, it is possible to make a perfect 90-degree angle clamp at a minimal price.
How do you use clamping squares?
Clamping squares are an invaluable tool in the shop when joining wood pieces together. They ensure that workpieces are accurately held together at a 90-degree angle. Clamping squares can be used for all types of perpendicular inner joints, such as t-joints or dado joints but can be used also on corners both on the inside and outside.
To set the clamping square, place it on the inside or the outside of a corner and secure it with clamps. For a tight fix use f-clamps or j-bolt clamps, for a flexible fix use spring clamps.
Are corner clamps worth it?
Corner clamps are much needed in a workshop. Whether building furniture, assembling cabinets, or joining large sheets of wood a set of corner clamps will come in handy. Having a pair of corner clamps in the workshop is worth it. However, corner clamps can be quite expensive, so it pays to make them on your own. With little care, it is possible to make a perfect 90-degree corner clamp, even with basic tools.
What can I use as alternative to corner clamps?
Although there are a few alternatives that could be used in case you don’t have any corner clamps on hand, this is more of a case of a last resort. Corner clamps are important, justified, and necessary for proper and quality work in the workshop. Investing in a few clamps will definitely pay off.
Depending on the situation, as an alternative to corner clamps a masking tape, tie-downs, or a 90-degree corner clamp may be used.
How to Make a Corner Clamp
The size of the corner clamp is 15 x 15 x 2,4 cm and is made entirely of birch plywood. The clamp can be used for all types of perpendicular inner joints as well as for assembling pieces of wood on the inside and outside corners.
To make the corner clamp you will need a table saw, optionally a circular saw, a jigsaw, or a trim router. Basically whatever tool you have at hand.
However, although it is possible to create the clamp using basic tools in the workshop, using high-quality tools such as a table saw can make the job easier, resulting in cleaner cuts, and requiring less effort to complete.
NOTE: The most crucial aspect here is precision. Regardless of the method you select to build it, your end goal is to create a corner clamp with a perfect 90-degree angle.
Step 1: Cut the wood pieces
I started with one piece of plywood board (16x40cm) I cut in half. Then I glued both pieces together.
To cut the board I used a circular saw track. You can also use a circular saw guide for crosscuts which will result in a more accurate 90-degree angle.
Step 2: Ensure the squareness of the clamp
At this moment the plywood board was not exactly square. You can see the tiny gap in the picture below. That is something I will address in the next step.
To ensure the squareness of the board run it several times over a piece of sandpaper until you get a perfect 90-degree angle.
Looks good now.
Step 3: Cut the shape of the clamp
Cut the shape of the corner clamp. The clamp is 15x15cm.
I also cut the tip of the clamp. It leaves space between the clamp and the wood pieces which comes in handy when applying glue. The clamp does not get in touch with glue directly.
Step 4: Draw the design and cut the inner parts
Draw the design of the clamp and cut out all of the inner parts.
- Cut out two notches on the inner side of the clamp. They will provide additional space for clamping. I used a jigsaw station to make the cuts, but a hand saw like a coping saw would also work perfectly fine.
- Use a ø 30mm Forstner bit, and drill a hole in the center. This hole can be utilized for extra clamping and is particularly effective when clamping mitered corners.
Step 5: Cut the clamping slots
Draw the additional slots on the clamp and cut them out.
TIP: I taped the corner clamp to a sacrificial board and used a trim router in combination with a router dado jig which made it quite easy to cut the slots. Although a hand drill or a coping saw would work as well.
(Be careful not to route into anything you don’t want to – like a workbench)
Optionally, you can cut out a half circle from the inner side of the corner clamp. This is not necessary though. It makes the clamp lighter and the design looks just nice.
And this is how the finished corner clamp looks.
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How to use a corner clamp
- Position the corner clamp on the inside of two pieces of wood.
- Secure one side of the corner clamp to the first piece of wood using clamps.
- Adjust the second piece of wood as necessary.
- Secure the second side of the corner clamp to the second piece of wood using clamps.
- Tighten the clamps to the required degree.
If you intend to glue the wood pieces together, apply glue during steps 3 and 4.
- Avoid over-tightening the clamps, as this may cause damage to the material.
- Before tightening the clamps, ensure that the pieces of wood are properly aligned and flush with each other.
- Use the appropriate clamps for the job, taking into account the thickness and size of the wood.
- Check the alignment of the pieces of wood periodically while tightening the clamps to ensure that they remain flush and perpendicular.
A corner clamping jig is suitable for various perpendicular inner joints like t-joints, dado joints, or rabbet joints. Typically, it is utilized on the inside of a corner, but it can also be used on the outside, depending on the shape of the joint.
How to clamp a miter joint using a corner clamping jig
There are a few different ways how to clamp a miter joint. The steps provided below describe how to clamp a miter joint using a corner clamps.
- Position the corner clamp on the inside of two mitered wood pieces.
- Apply glue to the miter joint.
- Secure the corner clamp to both wood pieces using clamps.
- Place a wooden counterpart on the outer corner of the miter joint.
- Secure the wooden counterpart and the corner clamp with clamps.
- Tighten all of the clamps to the required degree.
TIP: You can place a piece of wax paper right below the miter joint. You will be able to easily get rid of the glue excess keeping your workbench clean.
How to make a Corner Clamp Video
Watch the video below for a step-by-step guide on how to make a corner clamp (90 degree clamp).
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If you’re looking for a cost-effective way to hold pieces of wood together at a perfect 90-degree angle, making your own corner clamps could be a great solution.
I found out that precision is essential when creating a corner clamp, but even with basic tools like a circular saw, drill, and clamps, you can achieve the accuracy you need.
When using your corner clamps, be sure to align your wood pieces properly and avoid over-tightening the clamps, which can cause damage.
For clamping a miter joint, remember to check the angle with a square, apply glue evenly to both surfaces and use moderate pressure when tightening the clamps.