lathe + power feed + measure + z

[deji]

I have a question that has been in the back of my head for a while.

Say I am on a lathe, need to come in .500 on a piece. The way I would do it would be to face it off, then 0 it out. I guess "it" would be referring to the small handle with measurements, that controls the z. Would turn it 5 complete turns to equal it to .500. What if I wanted to power feed it? The power feed on all the lathes I used controls the apron to move it along the z. No way to measure that way it seems.

Only experience I have on a lathe is in school. For our little project, the way I was doing it was fine since the most I had to come in on a part was .185. On the final, the part needed 1.000 in, and was a pain.

So, just asking how it should be done correctly.

Thanks

[RICHARD ZASTROW]

Assuming manual lathe w/o DRO: Long stroke dial indicator with magnetic base set on lathe bed; contact plunger against carriage; set dial to "0"; feed appropriate amount. Long stroke indicators are available to 4" stroke.

[deji]

I used a dial indicator before, once, to check flatness before I grinded something on the surface grinder. Saw the instructor use it on the mill vise, and also on a part in the lathe chuck to see if it was perfectly round. I never knew it could be used to measure length. I will google around to see if I could find some examples.

No digital readout. Some of the kids actually had the toolpost slide on an angle. I have no idea how in the hell they measured the parts.

Thanks for the reply.

[RICHARD ZASTROW]

deji, Lathe compunds are often set at 29 1/2 deg. for threading. Ask your instructor about measuring rods and hard stops. (He may not be old enough to know about them) Before DRO's they were used on jig boring machines, jig mills and precision lathes. They are time consuming compared to DRO's but are quite accurate. That may help in your machining education. Good Luck.