fcspence - Dusty has correctly answered your question. Incidentally, thanks for posting your very first question - and as you described it is a "favorite headache"!
First of all - go into the house and take a Tylenol with plenty of water. That should help a little.
To be serious for a minute, I am one of those guys that swear by the 510. The only time I can remember swearing
at it was when aligning the fence. I had it perfect for a long time and then dropped it onto a concrete floor.
Don't do that!! That time I had to not only align it, but also had to straighten the cast fence base (514254). I know it only costs less than $20, but as I lost my cool for a while - just knew I had to fix it.
Well, trying to make a long story a little shorter - the da_ n thing just wouldn't stay put during the tightening of the two screws. Here is what I winded up doing:
This is important,
Use a #3 Phillips screwdriver here. #2 is too small!
1) Removed both screws put new lock washers under each screw head.
2) Got the fence as straight as I could and snugged the available screw.
3) Carefully removed the fence and snugged the second screw, without more tightening on the first.
4) replaced the fence and with both screws snugged down - re-aligned the fence. There was only a little wiggle left and I was careful to not move the fence any more than necessary. You can slightly tighten the outside screw a bit more here.
5) Carefully removed the fence again and carefully tighten the screws
a little more.
6) Re-checked alignment again as in #4)
7) Tighten those little suckers down.
The operation seems to be "how much to tighten". I figured that with two snugged screws - it ought to stay secure through a little more movement. It did!
Now it's been good for 5 years of a lot of ripping.