Copy of Rollie's Dad's Method

I searched google groups and got this:

Great method, Karl. IMO you should have posted it in the thread, above, that address's lathe leveling. I hope the OP there sees it and can relate it to his questions.

Bob Swinney "Karl Townsend" wrote in message news:VP2Xg.5712$ snipped-for-privacy@newsread1.news.pas.earthlink.net...

Rollie's Dad's Method of Lathe Alignment

Copyright 1997 by New England Model Engineering Society

What you need

A round bar The bar length should be about 1/3 to 2/3 the bed length. The bar must be of one diameter along most or all of its length. The bar does not have to be completely straight. Since Rollie has a car repair shop, he uses the shafts from junked shocks and struts. A dial indicator The end of the measuring rod should be flat. A means of mounting the indicator on the cross-slide. To do a vertical alignment the mount must be adjustable. A chuck of any type to hold the bar. Runout in the chuck is not a problem (for the same reason that a slight bend in the rod is not a problem).

What you DON'T need

A tailstock, perfectly straight bar, a collet or precision chuck or any tool bits.

Applying the method (Horizontal Alignment)

1.Put the bar in the chuck. 2.Mount the dial indicator on the cross-slide at the center height of the lathe. 3.With the carrige near the chuck end, adjust the cross-slide so that the indicator reads a convienient "zero" value like 0.100 4.Turning the lathe by hand, adjust the cross-slide so that whatever runout you have is equal on both sides of your "zero" (say .105, .095). 5.Pull the indicator's measuring rod back by hand to clear any irregularities and move the carrige to the other end of the bar. 6.If the runout is not also centered there (say .110, .098) then your lathe is twisted and a foot should be shimmed. 7.Repeat from step 4 until the runout at both ends is evenly divided on either side of your "zero".

Applying the method (Vertical Alignment)

1.Put the bar in the chuck. 2.Mount the dial indicator on the carridge so that it is directly above the center line of the spindle. 3.With the carrige near the chuck end, adjust the indicator mount so that the indicator reads a convienient "zero" value like 0.100 4.Turning the lathe by hand, adjust the indicator mount so that whatever runout you have is equal on both sides of your "zero" (say .105, .095). 5.Pull the indicator's measuring rod back by hand to clear any irregularities and move the carrige to the other end of the bar. 6.If the runout is not also centered there (say .110, .098) then your lathe is twisted and a foot should be shimmed. 7.Repeat from step 4 until the runout at both ends is evenly divided on either side of your "zero".

Why This Method Works

When the runout is evenly divided, at the zero point the runout is entirely in the vertical plane and the side of the bar is exactly one bar radius from the turning axis of the spindle. If the runout is evenly divided at both ends of the bar, the spindle is rotating in a plane parallel to the ways.

Common Error

Some people will turn the lathe to the point where the indicator reads "zero" and then move the carridge down to the other end to see if it still reads "zero". That method will only work if your bar is known to be perfectly straight. Do not confuse that method with this one.

I learned all this from a fellow member of the New England Model Engineering Society. Join us the first Thursday of every month at the Charles River Museum of Industry in Waltham, Mass.