If you're looking to add a professional touch to your woodworking projects, learning how to cut miter joints with an angle finder is a great place to start. Miter joints are clean, 90-degree cuts that fit snugly together, making them perfect for everything from picture frames to baseboards.

What is a miter joint?

A miter joint is made by cutting two pieces of wood at an angle so that they fit together to form a corner. The angle of the cut is usually 45 degrees, but it can be any angle.

Miter joints are used to join two pieces of lumber at right angles to each other.

A miter joint can be either perpendicular or non-perpendicular. A perpendicular miter joint is one in which the two pieces of wood are cut at a 90-degree angle. A non-perpendicular miter joint is one in which the two pieces of wood are cut at an angle that is not 90 degrees.

Miter joints are often used in the construction of frames, moldings, and door and window casings.

Perpendicular miter joints

Perpendicular miter joints are miter joints that measure 90 degrees. You’ll typically see joints like these in perfectly square rooms, picture frames, door frames, and the like. The miter cut angles in these joints are 45 degrees, and they’re typically easier to calculate and cut compared to other miter angle measurements.

One thing to keep in mind with perpendicular miter joints is that they can be more difficult to execute perfectly, especially if you don’t have a miter saw. Any small inaccuracies in your cuts will be amplified when the joint is put together, so it’s important to take your time and measure everything as precisely as possible.

Thus, even if perpendicular miter joints are easier to conceptualize and calculate, you’ll need to make sure that you make accurate cuts to make sure that both boards fit flush together.

Non-perpendicular miter joints

Non-perpendicular miter joints are miter joints that are not at a 90-degree angle. These types of joints can be used for a variety of purposes and can be created with different degrees of angle. This type of joint is often used in furniture and cabinet making, as well as in picture framing. Non-perpendicular miter joints are more difficult to create than perpendicular miter joints, but the added strength and stability they provide make them worth the extra effort.

Because they're not cut at a 90-degree angle, they can be more challenging to create, which can add an extra level of satisfaction to your work.

Non-perpendicular miter joints are often used for picture frames, molding, and other decorative applications. They can also be used for functional purposes, such as joining two pieces of pipe together.

Measuring with an angle

Angle finders are a must-have when measuring miter cut angles. After all, you’ll only get a well-fitting joint if you take precise measurements. This simple device can help you to quickly and easily find the angle that you need, which can make the process of cutting the joint much simpler. Here are a few tips on how to use an angle finder to cut a miter joint:

1. If you’re working with a digital angle finder, make sure that you always “zero” the tool’s scale. You can check the user manual to see how this is done. When the screen reads 0.0 degrees, then that means that the instrument has been zeroed. Zeroing the instrument ensures that its measurements are accurate.

2. Make sure that the arms of the angle finder are situated flush against the sides of the angle you’re measuring. Keep in mind that you’ll need to check if your angle finder measures interior angles, exterior angles, or both.

3. Once you have the measurement, divide that figure by two. For example, the corner angle you measured is 90 degrees, then the miter angle is 45 degrees. If the corner angle is 103.5 degrees, then the miter angle is 51.75 degrees.

Regardless of whether or not you’re working with perpendicular corners, you’ll be undergoing the same process. The first thing you'll need to do is measure the full angle of the corner you’re working with. You can do this by using an angle finder for more accurate results. Make sure that you know if the angle finder you’re using measures interior or exterior angles.

4. Measure out the miter angle on your workpiece and mark the line of the angle with a pencil. You can then use a saw to cut along the indicated line.

However, it’s important to note that in some cases, calculating a miter angle is not as easy as dividing the total angle measurement by two. In certain situations, you’ll have to do more complicated calculations to get the correct miter angle measurements.

Calculating for miter cuts

If you're cutting molding or any type of trim that has an angle, you'll need to make a miter cut. To do this, you'll need to know how to calculate angled miter cuts.

Figures with multiple sides

As mentioned above, in perfectly square rooms with perfectly perpendicular corners, calculating for a miter cut is easy. All the corners are 90-degree angles, and miter angles are half those angles. This means that the miter angles in this room measure 45 degrees.

However, you’ll also encounter irregular angles that measure more or less than 90 degrees. In certain cases, the same principle applies: you’ll need to measure the full angle of the corner, then divide the measurement by two. This will give you the miter angle.

Of course, there are rooms and objects that have more or fewer than four sides. In these cases, the most important thing to remember is that all angle measurements should total 360 degrees. For example, a square room has four sides and four perpendicular corners, each measuring 90 degrees. Altogether, the sum of these measurements is 360 degrees. The same goes for a figure with six sides and six corners, a figure with seven sides and seven corners, and so on.

Boards of different widths

All these calculations are well and good if you’re working with boards with equal widths. However, it’s always possible that you’ll have to work with boards with different widths, which makes measuring for miter angles a bit more complicated and calls for some pretty advanced math. You’ll likely need a scientific calculator or a calculator that can work with periodic functions, specifically sine and cosine.

Thus, one thing you’ll need to remember is that when you’re calculating the miter angles for boards with unequal widths, it’s not a matter of simply dividing the corner angle measurement by two. Because the boards have unequal widths, their miter angles will be unequal as well.

Thankfully, you won’t have to do much of the math yourself. There are various online calculators, such as the Omni Calculator, that you can use to figure out the miter angles for boards with unequal widths. It’s important to make sure that you calculate for the exact miter angles so you end up with a clean joint and two boards that meet flush against each other.