A miter cut is an angled cut that is commonly used to create picture frames, door frames, and molding. Additionally, miters can be used as a form of joinery and be incorporate many woodworking projects.
How to create a miter cut
Creating miter cuts are not difficult with the correct tools. The key is to take correct measurements and to get the correct calculations. Afterwards, the cutting and glue up process is simple.
- Take measurements
- Do calculations to determine your angles
- Determine the angle of the full piece
- Consider how many corners you will have
- Calculate the wood length
- Calculate the miter angle
- Mark your angles
- Set up the cut
At the end, I will go over some helpful tips to create better miters and how to get miter angle with the least amount of math as possible
Take measurements
The first step to creating miters is to take measurements. If you are replacing a door frame, molding, or some if you are incorporating your project into something with a pre-existing angle (like corner wall shelves), then you will want to measure the angle you are working with.
This is important because corners may not be a perfect 90-degree angle. You would not want to make perfect molding for a corner that is not a perfect 90.
Do calculations to determine your angles
Now that you know the angle that you need to create, you can now do the calculations to create the correct miter.
This part is one of the most difficult parts but it is easy to understand. First you will need to determine the angle of the full work piece and then determine how many angles that you will use. After that, you will be able to determine the angle of the miter.
Determine the angle of the full piece
The angle of the full piece will be the sum of all the angles. The two most common angles for the full project are 360 degrees and 180 degrees.
To calculate the angles of the full piece, you will find the total number of angles that you have, subtract it by two, and multiply it by 180.
So, if you are making a square box, you will take (4-2) *180 to get 360 degrees.
If you are making a door frame, you will also have 4 angles/corners. You will use the same calculation to get a total angle of 360 degrees.
If you are making an octagon, you will have 8 angles/corners. So, the calculation will be (8-2) * 180 = 1080
Consider how many corners you will have
Now you will need to determine how many corners that you will have. With that you will be able to determine the angle for each corner.
To determine the angle for each corner, you will divide the angle of the full project by the number of corners to get the angle for each corner.
For example, if you have a fully enclosed piece of 360 degrees and 4 corners, then each corner will be 90 degrees.
If you have a fully enclosed piece of 720 degrees and 6 corners, then each corner will be 60 degrees.
However, every corner does not have the be the same angle. If you have a 720-degree piece of 6 corners, you can have 4 corners be 150 degrees and the other two be 60 degrees. The key is to have all of your corners equal up to the full angle of your piece.
Calculate the miter angle
Now that you know the angle of your corners, you can now determine the angles of your miters.
To determine the angle of your miters, you will have to consider the wood thickness.
Same thickness
If both pieces of wood are the same thickness, then the miter angle is half of the angle of the corner. If your corner angle is 90 degrees, then your miter angle will be 45 degrees.
Different thickness
However, if both pieces of wood are not the same thickness, then you will have to more advanced math.
You will need to use the equation a = Arctan(n * sin(θ)/(m + n * cos(θ))) and then a will be the opposite angle of b = θ-a.
n is the thickness of the thinner wood.
a is the angle of the miter for the thinner wood.
m is the thickness of the thicker wood.
b is the angle of the miter for the thicker wood.
θ is the angle of the corner.
There is an easier method that this can be done if you are creating a 90-degree corner that I explain in the bonus section.
Calculate the wood length
The outside and inside wood lengths will be different and should be considered when taking measurements.
Interior corner: Longest side of the wood to match environment corner
Exterior corner: Shortest side of the word to match the environment corner
If your piece is going to be interior to corner, then you will want the longest side/outside angle of your piece to match the shortest side/inside angle of the environment.
If your piece is going to be exterior to the corner, then you will want the shortest side/ inside angle of your piece to match the longest side/outside angle of the environment.
If you are not incorporating your piece with any pre-existing angle, then you will want to ensure that the longest side/outside angles are used to determine the complete size of your project.
Mark your angles
Wheeew, now we got the hardest part out of the way. Now all you have to do is mark your angles.
If you have a miter saw or table saw with positive stops, then you will not need to mark your angles. However, I always recommend that you do so to ensure that you cut the correct length of wood.
To mark your angles, you will line up the bottom of the combination square with the side of the wood. Afterwards, you will adjust the angle of the combination square and then mark it on the wood.
Set up the cut
Now we will set up the cut. Regardless of the saw that you are using, you will want to cut on the outside of the line.
You will clamp the wood using the miter clamp if you are using a miter saw. Or you will set up your saw fence if you are using a table saw.
Join the wood
Before joining the wood together, you will want to clamp all of the pieces to ensure that everything fits.
Afterwards, you will glue and clamp. The key to clamping miters is to clamp everything at one time.
The best clamp for clamping enclosed pieces is to use a band clamp.
Not only is this process faster, but it ensures that each individual angle does not become slightly off, thus effecting the last angle.
Purchase a band clamp here: Amazon link
Minimal math method
The minimal math method is very useful but can only be used in certain scenarios. This method can only be used when working with 90 degree corners.
You will take two pieces of wood, place the corners on top of each other but with the wood at a 90 degree angle, and mark each piece. Afterwards you will connect the corners to create the angles.
Align wood pieces at a 90 degree angle
Lets say you have two pieces of wood, wood A and B.
After you ensure that the corners of the wood are both 90 degrees, you can place the corners of the wood pieces flush to each other with wood A over wood B.
Mark each wood piece
Double check to make sure the angle is 90 degrees and mark a line on wood B.
Next you will flip both of the wood pieces and do the following for wood A.
Draw miter angle
Afterwards, you will connect both of the corners of the marked wood to create a straight line.
This is great when working with wood pieces of varying thicknesses because it takes out the tedious math work when determining angles.
Conclusion
In this article I showed you how to create perfect miters by getting the exact measurements. I also when over how to make quick 90 degree miters by doing the no math trick.
Thank you so much for taking the time to read this article and I wish you luck on your woodworking journeys!
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