Yes, it is a scary thing. it makes my testicles do that strange crawly thing every time I use it.
Paul Tatum squares with a mitre saw. He's got some kind of funky blade on the thing that cuts very well. Chop, chop, chop, chop, and the block is square. Personally, I don't have room for a mitre saw, but it is tons quicker. Also, the thing intimidates me - hands so close to a spinning blade and all - I think I used his once, but it was a little scary. Hopefully, if Paul sees this, he will let you know what kind of blade he uses in his mitre saw. It makes a nice clean, smooth cut.
I use a fine cut blade. I initially bought it for cutting a counter top with my skill saw. It has about twice as many teeth as a ripping blade, and much smaller. The secret is to only shave the block. Normally I only cut a blades width off any side. Remember to use the bottom and the cut side as your vice reference surfaces, meaning put the block on the vice bottom, then back it up to the cut side then close the vice. This will keep the block square to the vice and the sides you used for the cut. The uncut side that contacts the vice jaw qill not be in good contact with the jaw and if it is extreme you can use a shim. If you square blocks on a mitre saw often you'll find a bunch of shims lying on the floor underneath it. Nice little wedges as thin as a quarter.
If you do choose to go the insanity route and trim blocks with a mitre saw be sure you never, EVER grip the block with any force. You should let the force of gravity hold the block down, and push back to the rear gently to keep it in place. If the saw grabs the block you want it to fly away freely and not take your fingers with it.
I don't recommend using a mitre saw for this, not at all. It's crazy and dangerous. Rad's disc sanding is much safer. I've been meaning to make a jig to hold the blocks. I think I'll make it a priority when I get back to the shop to work.
You guys sure make me glad I haven't had to think about squaring a block in 3 years!
