45 Degree Angles and Finish Carpentry Tips

Finish Carpentry Tips For getting Nice Tight Miters

As you probably know 45 degree angles cut on two pieces of trim, for example casing would form a perfect 90 degree mitered corner.

When trimming doors and windows this is considered the analogy but is seriously far from the truth when trying to achieve nice tight 90 degree miters.

There are so many little variables that can and do change this so called picture perfect analogy.

Let's take a look at some of these variables so you can get the nice tight miters for your own trim projects.



If you are trimming a door or window the first thing to look for is making sure the outer edge of the jamb is flush with the inside wall. If it is perfectly flush all the way around you are good to proceed.

If not then you will need to correct this problem and there are a couple ways to do this depending on your particular situation.

The jamb may be sticking in past the wall or it may be short of reaching the inside wall what ever the case go over to this page finish-carpentry-tips to find some solutions to fixing these problems.

When you are confident the casing will be flat as possible the next step is getting ready to cut the angles on both sides of the top piece of casing.

I will always start with the top piece of casing when trimming doors and windows.

For full instructions for casing a door go to this page casing-interior-doors. These instructions would be very similar for casing windows only the casing runs the total perimeter and in most cases connect together with 4-90 degree miters.

Tight Miters

One very important factor here for tight miters is being sure there is a back cut on the 45 degree cuts. This back cut or bevel will be so the face or outside of the casing will be longer so the two 45 degree cuts will meet at the face or outside of the casing together before the back of the casing meets together. Cutting this bevel on the 45 degree angle cuts makes tighter miters easier to achieve.

45 degree angles only work if the casing is perfectly flat.

If the casing is tipped inward this would cause the angle to change slightly. Practice with some scrap pieces of casing to figure out exactly what the angle is before cutting the actual piece that will be nailed on.

All of these miters should be glued and pinned and this is all explained at this page casing-interior-doors.

No matter what all miters need to be worked a little to get them perfectly tight. As you go and if you read through these pages you will discover that these techniques and finish carpentry tips will work.

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