Help with plumbing spindle

[abentley]

I have a prs alpha and I am tuning up the spindle, (z axis). I got the y gantry plumb, but the spindle is off by .020. There is not enough play in the spindle mounting plate to move the spindle into plumb. Any thoughts on the best way to get it plumb?

[garyc]

Alan...
You dont say which way (X or Y axis tilt) the Z is off, nor have you qualified the distance that the .020 applies to. I will assume that the .020 is over the length of the spindle body.

If the spindle needs to be moved in the Y direction, loosen the 6 bolts at the rear of the Z extrusion that hold the spindle and plate to the extrusion and tilt the spindle and plate as required. In some cases boring the holes a few thousandths larger is required.

If movement in the X is required, loosen the same bolts and slip in .002 to .005 shims between the spindle adapter plate and Z extrusion in either the top or bottom as required.

Recheck with your square. I consider a surfacing the table, especially with a large diameter bit as the final confirmation of proper spindle orientation.

More info here: http://www.shopbotblog.com/index.php/2008/12/tuning-up-the-prs-gantry/

[abentley]

Gary
I am using a dial indicator chucked into the spindle at 4" from center. It is the Y direction. The best I can do is a.0005 difference which I can live with. Thanks for the link thats my next step.

[garyc]

Alan...
OK... .020 over 8" swing. From center out to 4" off .010 On a 1" deep cut the error from vertical would be .0025, virtually unmeasurable. Were your parts showing non square edges?

Have you verified that the plate you are tramming over is both flat and a consistant thickness? Has it been placed over a freshly surfaced spoilboard? And lastly, have you verified the height of that plate using a dial indicator in the Z at the 4 corners? (without moving the Z vertically, of course)

A dial indicator in a trammel gauge mounted in the z is only as accurate as the pre qualifying that you do. The steps above are what is usually required to make sure that you are measuring over a true surface. In the end, your surfacing bit tells the truest tale with the least money and effort.

[abentley]

Gary
I have never been really happy with the parts I cut with the link, and could not get my dados to match e cabs. The last kitchen took to much playing around to make the fit. When I set the shopbot 4 years ago, I used a framing square on the spindle to set it. So I figured I would start from the beginning and tune in the shopbot and go from there. Thanks