A miter joint joins two pieces cut at matching angles, usually 45 degrees each, to form a 90-degree corner. It hides end grain and gives frames a neat look. With a miter box and a hand saw you can make accurate corners if you work slowly.
What You Need
- Miter box and a back saw that fits it
- Pencil, tape measure, and a square
- Sanding block with fine paper
- Wood glue and a small brush
- Band clamp or corner clamps
- Spare scrap of the same stock for test cuts
Cutting the Angles
- Decide the outside length of each frame side. Mark it on the long point of the miter, not the short one.
- Place the first piece in the miter box with its good face toward you and press it against the fence.
- Line up the saw in the 45-degree slot. Make a few light pulls to form a groove, then continue with long, steady strokes.
- Flip the second piece so the angle runs the opposite way, then cut it in the matching slot.
- Repeat for the remaining sides, cutting in pairs so that opposite sides come out the same length.
Fitting and Gluing
- Hold two cut ends together. Check the corner with a square. If a gap appears on the outside, the angle is slightly too large; if inside, too small.
- Trim a hair at a time by sanding the cut face on a block, keeping the sanding even.
- Brush a thin coat of glue on each mitered face. Because miters expose end grain, let the first coat soak in briefly, then add a second thin coat.
- Assemble the frame, apply a band clamp, and snug it gradually. Check the diagonals for squareness.
- Wipe off excess glue, then leave it clamped for the time on the glue label.
Troubleshooting
| Symptom | Possible cause |
|---|---|
| Open gap at the tip | Saw blade drifted or slots worn |
| Corners shift while clamping | Too much glue or uneven pressure |
| Pieces differ in length | Cut one at a time instead of in pairs |
Many woodworkers add a spline, a small dowel, or a corner key for extra strength, since a plain miter relies on end grain glue.
Keep the saw sharp and the miter box clean, because chips and dust under the work can tilt the piece and spoil the angle. Support long pieces at the far end so their weight does not pull them out of the box. When you finish a frame, hold it up to the light to check each corner and look at the diagonal measurements once more before the glue sets.
FAQ
Can I make a miter without a miter box?
You can use a marked line and a steady hand, or a guide block clamped to the work. A box is simpler for beginners.
Why does my corner not close?
Often the angle is a little off or the stock is not equal in width. Test on scrap and adjust.
The Short Version
Cut matching 45-degree angles in pairs, test the corner, trim gently, and clamp evenly. Reinforce if the frame will carry any weight, and follow the tool maker’s instructions.