How to Cut a 22.5 Degree Angle on a Miter Saw

Learning how to cut a 22.5 degree angle on a miter saw can be a make-or-break step for finishing many types of woodworking projects. While it is easier to make a 22.5 degree cut on a table saw, it is possible to safely make this angled cut on a miter saw.

Reasons to Cut a 22.5 Degree Angle on a Miter Saw

There are several projects in which a 22.5 degree angle cut is important. The most common reason woodworkers look to create this angle is for creating geometric shapes. Other popular projects include bisecting 45 degree cuts.

Let me look first at creating a triangle before I move on to discussing the more complex octagon.

Cutting 22.5 Degree Angles to Create a Right Triangle Frame

To help make sense of why I would need a 22.5 degree cut to create a triangle, consider the following:

Many families have a flag they wish to place on display. Many American flags are sacred to their owners, especially if they represent a family member who died in the line of service. These memorial flags are often folded into a triangle.

Creating a triangular frame to preserve such flags has created a need for understanding 22.5 degree cuts.

Quick geometry review: triangles have three sides. The interior angles of all triangles add up to 180 degrees. In an isosceles triangle, two of the legs are of equal length as well as two of the angles. 

If a triangle has a 90 degree angle, also known as a right angle, then the other two angles must be 45 degrees.

Now, when it comes to carpentry, I want to create tight butt joints where the 90 degree angle is formed as well as the two 45 degree angles. How do I do this?

Creating a Miter Saw Jig to make a 22.5 Degree Cut

We will create a jig which will allow me to form 45 degree angles. The jig itself will also be used with my triangle project!

For my triangle project, I need to divide a 90-degree cut by two and a 45-degree cut by two. Ninety degrees divided by two is 45 degrees. Forty-five degrees divided by two is 22.5 degrees.

Cutting a 45 degree angle on most of the top miter saws is simple:

1. Unplug your miter saw.
2. Unlock your miter saw’s swivel.
3. Pivot to 45 degrees.
4. Lock your miter saw’s swivel.
5. Put on hearing and eye protection.
6. Plug in saw.
7. Make your cut.

If you are creating my triangle, you can cut two 45 degree angles. If you wood glue, screw, and clamp those together you will have a 90 degree angle! However, for my project to work, I will also need to cut four 22.5 degree angles.

Using a Miter Saw Jig to Cut a 22.5 Degree Angle

Luckily for us, by completing the last step, you have already created a 45 degree jig that will help me create my 22.5 degree cut.

Miter saw measurements can be confusing. Even beginner miter saws cuts at a 90 degree angle when in its standard position. Swiveling the miter saw reduces the angle from 90 degrees on one side of the cut while increasing the angle from 90 degrees on the other side of the cut.

To create a 22.5 degree cut, you would have to swivel all the way to 67.5 degrees. No miter saws swivel that far. Most stop at 45 degrees. 

So, if I can’t swivel outward to 67.5 degrees, I need to use a jig to decrease the distance in which the saw needs to swivel. In swoops my 45 degree jig to the rescue.

Clamping Your 22.5 Degree Jig 

1. With the saw unplugged and in standard position. Your miter gauge should be at zero as though you were about to perform a 90 degree cut.
2. Place the long edge of your 45 degree jig along the safety fence on the left-hand side of your miter saw. 
3. Lower your saw blade as if you were cutting a piece of wood.
4. Slide the long edge of the jig along the fence until the tip of the jig touches the saw blade. The visual this creates should be like a quarter of a pie with one “slice” of wood touching the fence and an equally-sized empty “slice” between the jig and saw blade.
5. Clamp your jig securely in place.

Cutting Using Your 22.5 Degree Jig

Now that your 45 degree jig is in place, you are positioned to create your 22.5 degree cuts. You will want to bisect the empty space between your saw blade at its standard 90 degree position and the angled-edge of the jig.

1. With jig clamped, swivel your miter saw leftwards towards your jig to 22.5 on your miter gauge.
2. With the saw still unplugged, place your piece to be cut along  your jig to visualize your cut. The long edge (also called the outside edge) of the piece you are cutting should be along the jig.
3. Remove the piece to be cut.
4. Put on hearing and eye protection.
5. Plug in the saw.
6. Place the piece to be cut along the jig while keeping hands out of the saw’s path.
7. Power the saw to its full speed, then slowly cut through your wood.
8. Release the saw’s trigger, allowing it to come to a complete stop, before allowing it to raise.

You have now used a miter saw to create a 22.5-degree angle cut. For my triangle project, you will need to use this jig to create two 22.5-degree cuts with the saw swiveled to the left. 

Then, you will reverse operations. Place the jig on the right-hand side with the long edge along the fence. Clamp it securely in place, then repeating the instruction above, make two more cuts with the saw swiveled to the right at 22.5 degrees.

If all the cuts are done correctly, you can pair and mate the four 22.5-degree cuts and the two 45-degree cuts to form your triangle.

We always recommend using wood glue when putting woodworking projects together. Wood glue has greater holding strength than nails or even screws if joints are held under pressure while the wood glue dries. 

22.5 Degree Angles in Octagons

Briefly, let’s look at why 22.5-degree cuts can be important in octagons. 

Going back to high school geometry class, regular octagons have eight sides whose sides and angles are all equal. The sum of all of the interior angles of an octagon is 1,080 degrees. That may be an intimidating number, but let’s break it down.

• Imagine a square. It has 4 equal sides and 4 angles of 90 degrees. As I add sides to create pentagons, hexagons, septagons, and then octagons, those angles continue to grow wider or more obtuse. 
• For the octagon, there are 8 interior angles totalling 1,080 degrees. If I divide the 1,080 degrees by its 8 angles, I get 135 degrees per angle. 
• A straight line is 180 degrees. Subtracting my 135 degree per angle of the octagon from a 180 degree straight line, I get 45 degrees. What is half of 45 degrees? It is 22.5 degrees!

The mating joints of all regular octagons will be two 67.5 degree cuts. You can creatively combine 22.5-degree cuts to form intricate octagons.

Also, learn how to cut 15 degree angles and 30 degree angles with your miter saw.

Conclusion

By walking through the creation process of a simple isosceles right triangle frame, I have learned how to create a 45-degree jig that allows for the creation of 22.5-degree cuts. By mastering how to make these severely acute-angle cuts using jigs, many new and exciting opportunities for woodworkers are opened up.