Miter bar adjusting?

[keith ouellette]

This is a follow up question for my miter dial indicator set up.

I have a steel miter bar I bought last year. It has three spring loaded bearings on one side (front, middle and back) and on the other side it has three alan screws to adjust the bar (At the same positions as the bearings) to make it slide in the slot without allowing it to move from side to side.

My question is:

If the set screws are turned out enough to take up any play between the bar and the miter slot could the bar be crooked in the slot and still slide?

Would this through off my measurement between the dial indicator and the blade?

would having the dial indicator placed at the center of the miter bar negate the problem of the bar being crooked?

[Tom Veatch]

...

If the set screws are turned out enough to take up any play between the bar and the miter slot could the bar be crooked in the slot and still slide?
Yes. By crooked, I think you mean one side of the bar is closer to, say, the right side of the slot at one end than it is at the other. But that won't matter if the adjustments have taken out all the side-to-side slop. If that's not what you mean, ignore the remainder of this response.

Would this through off my measurement between the dial indicator and the blade??
As long as the side-to-side location of the miter bar relative to the slot does not change as the bar moves fore and aft, the indicator would never know the bar was crooked. Think of it this way. Take a perfectly straight bar, perfectly fitted to the slot. Then machine half the bar away with a tapered cut between the set screw positions. That would simulate a crooked miter bar, but it wouldn't affect measurements from an indicator mounted on the bar since the set screws hold the bar in the same side-to-side location within the slot. As long as the bar doesn't move from side to side at the indicator location, the measurement is unaffected.

would having the dial indicator placed at the center of the miter bar negate the problem of the bar being crooked?
Not necessary.

[keith ouellette]

Thanks tom. I'm ready to go.

[Lee Schierer]

Tom is correct. I would suggest that you see how wide your miter slot is and how wide your bar actually measures. While the set crew adjustments are convenient, they are limiting your total accuracy. They make adhesive UHMW tape in various thicknesses. I've personally have it .003 and .005 thick. You can clean off the side of your miter gauge bar with lacquer thinner and apply a .003" or .005" thick strip of UHMW tape to the side and totally eliminate side play no matter how much of your guide bar is engaged in the slot.

I've done this with my craftsman miter bar and the UHMW tape lasts several years. Because the tape is as slippery as teflon, the miter bar slides very easily despite having less than .0005" of side play.

Pricking the side of the miter bar only lasts a few months if your saw get much use. The problem is you don't notice that the pricks are wearing and your side play gets bad before your notice it.