Thread: Correct way to make this

You used a three jaw chuck?

Stuart

Yep.

Do you have a 4 jaw small enough to grip it and a DTI?

Originally Posted by Stustoys

Do you have a 4 jaw small enough to grip it and a DTI?

Got the standard 4 jaw chuck that came with the lathe but it's a pain to use, I do have a Dial indicator.

Hi Tiger,

I'm assuming the runout has come from the fact that you turned one part and then removed it from the chuck, re-chucked the newly turned part and turned down the other sections?

If this is the case then that's the issue. Once you turn something in a 3 jaw and remove it, you will loose concentricity. On some parts where the tolerances are "big", it will not be an issue but when you are turning small diameters to within "reasonable" tolerances, you need to re-think you order of operations.

There are a couple of ideas, you can turn the large diameter part, and then hold that end in a collet, in the lathe. This will hold your workpiece within greater tolerances (less runout) and then go about turning the smaller, longer diameter. I think you will still need to support the end with a tailstock since it's very small and will otherwise flex. Even so, you will need to take relatively light cuts to avoid this all the same. If the tool post is getting in the way, maybe start with a longer piece of material, turn down to required diameter and to length and then cut to length.

Other option is to do all operations with it in the 3 jaw and without removing it. You will need more material to allow the amount of "stuff" held by the chuck. The other benefits (although minor) to the above ideas are that the workpiece will not be marked with the 3 jaw chuck.

Others here may come up with a better idea, I'm still learning, but these two ideas were the first that came to my head.

Good luck!

Simon

I would always try to turn something like this between centers. If the tail stock or live center is getting in the way, overhang the tool some more, or grind a hss tool or buy a diamond shape insert tool so you will clear the live center. Or you can make the part 1/2" too long, and when you drill your centers turn the first 1/2" down to a little less that the finished size. That way your center clearance is not a problem. Once all the turning is done you can cut the extra bit off. As long as your centers are clean and have no run out the job should be perfectly concentric.

Ew

Thanks all, must have been a bit of flex, cutter is pretty short so couldn't extend it much. You've given me some ideas though about what i can do and appreciate that.

It just so happens i was faced by this problem this arvo, making a 1/2" tapered mandrel. Drilled and turned the ends down to .480" for .750". Plenty of room for the cutter and the drive dog.

Ew