🔨 Miter Joint Calculator
Set corner angles, cut lengths, blade settings, and glue area for frames, boxes, and polygon projects.
| Material | Density | Hardness | RPM |
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| Sides | Corner | Miter | Use |
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| Blade | Teeth | Best Use | Max RPM |
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| Project | Mode | Angle | Stock |
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A miter joint is made by cutting each of two parts across the main surface, normally at a 45° angle, to form a corner that is usually 90° It can have any angle bigger than 0 degrees. A miter joint is made when two wood pieces, cut at an angle near their original corners, join together. You cut two boards in exactly opposite angles and put them together to form a wanted corner.
A miter joint is used mostly for beauty, because it hides the end grain. It shows the face grain around the whole joint. A butt joint would leave the end grain visbile on one side.
Miter Joints: What They Are and How to Make Them
It is stronger and better than a butt joint, because the 45° ends give a big area for glue. Even so a miter is the weakest among several options. They are harder than butt joints and add no strength in some materials.
In MDF they are probably even weaker. Finger joints are best vertically, while half-lap or bridle joints are best horizontally.
A plain miter joint has a big problem. Its strength depends entirely on 45° end-grain glue joints, which are much weaker than side grain to side grain glue. Perfect 45° cuts also take a lot of effort.
A mitered box has eight edges cut at 45°, and even if the table saw blade tilt is only a bit off, that mistake grows and causes gaps.
To check cuts, use a 90 degree square. Press the parts flat against it and slip them together at the joint. If there is a gap at the outer corner and base, the blade is tilted past 45 degrees.
If a gap shows inside but the tips touch, tilt the blade a bit more. Good advice: cut miters a bit under 45 degrees, say 44.9 degrees, so that the ends close everything up without a gap.
You find many options for 90 degree corner joints, such as splined miter, lock miter, keyed miter, doweled miter joint and biscuit miter joint. Strengthening a miter joint with a spline after glue is another good idea. Clamps, wide tape, rubber bands or hose clamps help to hold miter joints during glue.
Good glue works surprisingly well if you want to avoid mechanical fasteners for beauty. Miter joints show up in picture frames, crown molding in outside corners, door casings, baseboard outside corners and decorativeaccents.
