I have failed four different ways at making miter joints.

Goal was to make a mitered joint in a 60" long cabinet, 3/4" thick, about 18" depth. Here are the ways I have tried and failed so far:

1. Table saw. Its a dewalt contractor saw and I think there is just too much blade wobble or wander. I tried this on the smaller side pieces, there is no way I could even begin to hold the 60" long piece for a crosscut.

2. 90 degree folding miter bit in a router. This almost works but its painfully slow and leaves ridges in the finished product, and has some bad tearout at the end if you don't clamp a sacrificial piece on the end. Even if you move the fence back a hair and do a finishing pass, there are still ridges no matter how slow you go. Its a decently high quality carbide bit.

3. Festool track saw. It makes a nice consistent cut, but there is no click stop at exactly 45.00 so you have to rely on calibrating the angle yourself. Picture attached, this is where the saw maxes out on the angle and is roughly 45 but not close enough. Interesting that the angle gauge actually goes to 47, and the gauge is so fat you can't really get it more accurate than about a half degree? This would work but I can't get it set within the tenth of a degree or so tolerance to actually make it fit. You can see that when I use the corner clamps in the picture, its off by enough that the gap won't close.

4. Lock miter bit. Threw this one in here for a bonus, have not actually tried it on the 60" long piece because its supposed to be used on the table only, not hand held, and there is no way I could support the 60" piece horizontally while keeping it flush thru the table. I have used this successfully on small boxes.

I'm aware of the technique where you set the angle at a bit past 45 so that if there is a gap it shows up on the inside instead of the outside. That's still not ideal because... I need a square box. Anyway, I'm about to give up and just make this a rabbit joint, but I'm listening if anyone has any ideas on how to improve this.