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HI Group:

I was goofing off trying to figure out rollie dad's method of headstock alignment and see if my headstock is REALLY aligned or not. .

Lathe is an Emco (not enco) V10 Maximat. Bed has been leveled using a precision .0005 /ft level

I measured not quite 3 thou total indicator runnout (TIR) at the headstock end with my old Union 6" 3 jaw chuck , and 15 thou TIR at the end of a 14" long ejector pin (ground, 3/4" dia).

Following the formula, I think you divide both readings by two to get the "near and far end average"-- I get 1.5 and 7.5. Subracting as per Rollie method, does this mean my headstock is out 7.5 - 1.5 = 6 thou over the 14" length?

And in which direction is the headstock misagligned--- away from the operator or toward the operator? I am not sure how to tell with the dial indicator reading...

I can cut a 4" inch straight piece of steel chucked at one end with almost no taper, and with tailstock support, can easily cut 12".

Am I "twisting" the lathe with the tailstock to turn with almost no taper, or am I doing something wrong in measuring the alignment???

Steve

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Your goal is to bring the 2 averages as close to be identical as possible. Regarding if the work piece is away or towards the operator, the easiest way to tell is chuck up your indicating stock and zero out the indicator. The slowly move the carriage down towards the tailstock. If the movement of the carriage moves to the negative side, then the work piece is away from you, and if the indicator moves towards the plus side, then the work is closer to you. I went through this process on a 7x12 import and learned quite a bit. It may be that your tailstock is pulling your work piece closer to alignment, so little or no taper would result.

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Just touch the test bar, and you will see the indicator deflect. Then you know which way is near/far on the dial.

As for the adjustment, you need to make 3 readings. One at each end of the bar, and one in the middle. If you get a consistent slope, ie. the 3 readings would plot out on a straight line, then the headstock is indeed out of line. if you get a confusing reading that indicates either a barrel or opposite-to-barrel shape would be cut, then the bed is twisted (or worn). This is easier to figure out by adjusting the tailstock setover until the indicator reads the same at both ends. Then you check the middle. If it reads the same, everything is now perfect. If it reads different, the bed has twist or wear that is throwing everything off, and you are compensating as best as possible with the tailstock offset.

Hard to tell. If you get the indicator to read the same at both ends of a bar held by the chuck and the tailstock, and then back out the tailstock ram, the center hole in the bar should stay right in front of the tailstock center. If it wobbles around the tailstock center, the bar has a little bend in it, or wasn't held straight by the chuck, etc. If it orbits consistently to one side of the tailstock center, then it shows that you ARE forcing it into alignment by the tailstock center, and the spindle axis does NOT point right to the tailstock.

Jon

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