lathe work question

guys, how can i make a holding tool to keep my piece im makeing to be true , ( my piece im trying to make is similar to a head button ,but with a longer neck, to place set screws in neck , but when i face cut the piece off of stock, remove the bolt and put the neck in the lathe to face the other side, my center hole, is off center now, what did i do wrong,

A picture of your setup would be helpful. The easy way to keep everything true on the important side of a head button is to chuck a piece of bar stock and finish everything at the same time. You can then cut it off and use the flange area against the chuck jaws to hold the piece flat to finish the back side. You can use ground shim stock or feeler gauges to space the part out to avoid chucking on the radius. If you have a decent chuck, the piece should be centered within .002" as well. A Bucks type adjustable chuck will allow you to get even closer if needed.

If you have to chuck an existing disk shaped part that is finished on the back side, it gets harder. I use parallels to space the part out from the chuck face. An even more accurate method is to face a piece of heavy tube on both ends to the correct length and use it as a spacer. That assumes your part is bigger than the hole in the chuck. Light rubber hammer blows as you tighten the chuck jaws keep the part against the spacer and the chuck.

All this assumes that your lathe and chuck run at least an order of magnitude better than the part you want to make. Measure them first, then check your part after it's in the chuck.

Lohring Miller

For small parts I will machine a piece of stock into an arbor with a nice slip fit to the hole. As long as you don’t remove the arbor from the chuck it will spin true. Frequently the friction of the fit is enough to drive the part, or I will just masking tape it to the arbor. In your case you could use your set screw.

ok thanks guys, now i see what i need to do , thanks guys,

When I really want something to be accurate, I use soft jaws or a soft collet. Either one will give great results.

Bob

like has been said do all you can except for the cutoff and finish on the other side and then you can indicate it back in if you don't have an adjustable chuck but probably not necessary .

Im a big fan of collet closers for turning stuff accurately......you can remove the part to test fit it, put it back and it will still be true.....I make wheel hubs for my r/c cars, and they end up less than .0002 out. Cant use collet closers for everything, but they sure are handy when you can! Also nice for cutting the back side of a part, and its close to the head, as jaws can get in the way!