Thread: How to do accurate miter joints

Originally Posted by AlexS

I do my mitres on the disc sander. Mark the mitres with a marking knife on the outsides. Mark the opposite sides together, so they are exactly the same. Set up a fence on the table of the sanding disc (or belt sander) at about 45 and sand two test pieces. Check if they form 90 when you put them together. If they don't, adjust the fence. When the angle is correct, sand your mitres. As you get to the cut a small feather of wood will come away. When that happens, the mitres are correct.
As Jack says, mitres on boards more than about 50mm will inevitably open up. To prevent this, and for strength in any picture frames, I put in slipfeathers (splines).

I finally gave in and started using the sander like Alex a while back and it certainly works brilliantly! I also went to a lot of trouble making a dedicated 45 sled for the sliding table saw for doing frames and the like and it worked well on the usual timbers I tried it on like Silky Oak and Red Cedar. However, this week I tried cutting some 65mm wide Scrub Leopardwood and the joins looked awful - something to do with blade deflection in such tough wood I suspect so it was off to the sander to true them up - all good now