Need some advice on turning a 1.5 316L SS round

[GlennW]

When I make parts like that (meaning two similar parts) I cut the stock to a length that will make two and leave a little extra.

The I hold it in the chuck and turn one of them and then flip it and turn the second one.

Then just part them and face off the parted end to the proper length.

[heavyg603]

When I make parts like that (meaning two similar parts) I cut the stock to a length that will make two and leave a little extra.

The I hold it in the chuck and turn one of them and then flip it and turn the second one.

Then just part them and face off the parted end to the proper length.

I'm heading in that direction I think. Was just hoping to do an operation or two on the stock piece and waste less I guess.

[GlennW]

The only waste when doing it that way is what is needed to part the two pieces, which in my case is with a .078" parting tool.

[heavyg603]

The only waste when doing it that way is what is needed to part the two pieces, which in my case is with a .078" parting tool.

Provided I can get a good quality profile cut that's all I'd waste too I'd guess.

[heavyg603]

Ok a little more on this. While I'm still building my bering fingers, I finished up the piece of stock I was on and started another 12" long 1.5" diameter piece. I decided to try and use my 3 jaw chuck and a dead center in the tail stock this time, trying to get it held better during turning. First time trying this for me!

What I did in this case was to mark the center of the stock with a center finder, chuck up the piece, indicated it to within +/- .001 on the far unsupported end, brought the tail point to rest on the center, checked it with an indicator that I had it close ( .001), center drilled it on my press, remounted, lubed and tightened up the center, checked it on the indicator which showed I was now about .002 off (errrrr!) but figured I'd fix that during the turning to the diameter I needed.

Now this is the first time I ever used the center, and I wasn't totally happy with my work result. While I had no slippage in the center, and I did get a much better finish, it still wobbled a bit especially when parting it. Guess I just expected it to be a little more rigid, specially since I was only parting off about 1.5" from the center end.

[Harold_V]

Some things to consider.

Centers should NEVER be drilled outside of the setup in which it will be used (assuming you're chucking the material). The center should NOT be relied upon to cause the material to run true. That causes eccentricity between the center and turned part, as some of the crazy motion that results translate to oscillation of the tailstock quill, as well as the body of the tailstock.

It is not a good idea to part when a center is engaged with the material. That is an invitation to disaster.

Harold

[heavyg603]

Some things to consider.

Centers should NEVER be drilled outside of the setup in which it will be used (assuming you're chucking the material). The center should NOT be relied upon to cause the material to run true. That causes eccentricity between the center and turned part, as some of the crazy motion that results translate to oscillation of the tailstock quill, as well as the body of the tailstock.

It is not a good idea to part when a center is engaged with the material. That is an invitation to disaster.

Harold

Thanks for the tips! That makes sense with a lot of what I experienced. Some follow on questions based on your advice:

- since I can't fit the stock through the spindle, can you suggest an alternate method of doing drilling the center? Only other thing I could come up with was using my steady rest just to drill it.

- if parting with a center is a bad idea, and I can't do it within close proximity of the chuck, are there some known good alternatives? Was considering just profiling with the center and then just using my chop saw for cutting to the approximate length.

Thanks!

[Harold_V]

- since I can't fit the stock through the spindle, can you suggest an alternate method of doing drilling the center? Only other thing I could come up with was using my steady rest just to drill it.

The whole idea is to drill the center on location, not to drill it and then re-install the part later, in the hopes that the center runs true. The real problem isn't in drilling the center, as that can be done unsupported (with the material held only in the chuck). The problem is the face. If the part isn't square, centers can be troublesome. If the part must be faced, first, then you must grip the material in a four jaw (so it can be dialed true), then a steady employed to face the material. I'd even go so far as to suggest that the steady be removed before drilling the center hole. Once drilled, you'd do the work without removing the material from the chuck. That way the center is on true center, eliminating any oscillation potential at the tailstock.

- if parting with a center is a bad idea, and I can't do it within close proximity of the chuck, are there some known good alternatives? Was considering just profiling with the center and then just using my chop saw for cutting to the approximate length.

A very nice way to machine parts is to use soft jaws. That's assuming your chuck is large enough, and has master jaws. In that case, you can start with sawn material, slightly too long, to allow for facing. The part is roughed on one side, then the other, then finish machined. That's a little extra work in setup, but the end result is well worth the effort, especially if multiple parts are in order.

That said, I commonly use soft jaws for even one-off parts, as the advantages of soft jaws are hard to beat. Parts are held well under a thou in run-out, are square (depth stops in the jaws ensure perpendicularity) and are held at a given orientation, so linear dimensions are easy to control. Best of all, parts are held without any damage. That's assuming you understand how to machine the jaws properly.

One thing you can do if you intend to start with long pieces of material is to make the part on one end, or even both ends, assuming you can grip the first piece without damage, then part the pieces near the chuck. You grip the piece being parted, with the excess material hanging out of the chuck. That presents the best possible scenario for parting, as you can part very close to the jaws, which presents the maximum rigidity.

Harold