Swiss machine turning threaded stock

[tea hole]

A friend and I were discussing some parts and the question was posed how we would individually go about making them. After thinking for a bit, I answered that I'd consider trying a swiss machine if the conditions were right. I've never tried this, but i'm curious. If I had, say, centerless od ground threaded stock of some sort, say Acme or Ballscrew type, is there any reason why one couldn't make one diameter for a bearing on one side, cut a keyway with live tooling, then feed the bar through to turn a similar cut and mill a similar keyway on the other end. Think Bridgeport mill X axis lead screw.

What do you think?

[MikeMc]

I have run threaded stock in my Swiss machines. SO the answer for me would bve "Why not?" A few things you would have to consider is the length of the part, the diameter of the part, and the precision of the cuts versus the OD tolerance of the stock.

[tea hole]

for arguement's sake, if the tolerences on the bearing section were, say, +/- .001 leaving material for grind, there is really no reason a swiss couldn't hold that on any given tuesday, and the addition of the threads would add a certain amount of error, but even on a Bridgeport type thread length, at 40 some inches, as long as the sub spindle was thru, there isn't really any reason it wouldn't work, is there. That was my thought, but I've less swiss experience then the opposing party, and didn't want to "talk out my ass" if you will. Maybe I will re-visit the arguement and if all else fails, find a swiss I can borrow to test my theory. Thanks.

[MikeMc]

If the tolerance of the bearing section had to be held at +/- .001, and the OD of the thread was +/- .001 then we could easily hold the tolerance of the bearing section. The threads would not really add any error as long as the OD was consistant. "Borrowing" a $200K+ value machine might be an issue.

[tea hole]

My apologies, I should explain.
I am an applications engineer. I have access both at work, and at two different learning institutions if I can give a reasonable explaination as to why I would want to use the machine.
It was a hypothetical part, so I was just *assuming* it would need a high enough surface finish that it may need to be ground. my largest fear was threaded barstock OD consistency causing a binding condition in the guide bushing and/or the bar wanting to thread itself out or back in assuming the machine is a stationary guide bushing machine.

I appreciate your conversation about this subject.

[tea hole]

I have run threaded stock in my Swiss machines. SO the answer for me would bve "Why not?" A few things you would have to consider is the length of the part, the diameter of the part, and the precision of the cuts versus the OD tolerance of the stock.

I spoke to another apps guy who specializes in swiss and he seems to believe that "you would only get chatter that they've tried before and it didn't work".

Respectfully towards him, I'm not convinced. Without divulging too many particulars, could you clarify what kind of thread you turned and what sort of operations you were doing?

I will be getting a machine in the showroom next month and will try exactly what i'm thinking just to see and let you know how it works for me if you are interested.

[MikeMc]

We ran 8-32 threaded rod, and also a small Acme thread. The 8-32 just needed a fine turn from a needle point up to the thread OD about .200" long and a cut off. The Acme thread required a turn, a milled flat, and a cutoff. It amazes me how many things I have done with both cam and CNC Swiss machine that apps guys said I couldn't do. Most apps guys never had to make a profit from actually turning parts on a machine......no offense.

[tea hole]

None taken. I was a machinist for 8 years first. This is my first year in apps. I agree whole heartedly with that as a general statement. Like I said, I agree with you on the turning a thread. I will simply give it a try and either prove he is right, or you are. Simple as that. I obviously put more stock into your word than his (I did check out your company website), no matter how much I respect him as I'm willing to take a (as you pointed out 200k+) machine for a test drive to find out. Some people see things aren't an *ideal* cutting condition and won't even try. I hope to not fall into that. Thanks for the input. I'm glad I found someone who has a different opinion then the "norm".

[glenthemann]

I have to agree with Mike, if you can imagine it, then you can do it, dont let anyone tell you otherwise until you prove it to yourself.

If like you said, you had your threaded stock centerless ground then you should have no problems. Centerless ground it should be bang on size throughout the entire length of the bar. There would obviously be a little less inherent rigidity depending on the pitch, but personally I cant imagine any problems if it is not something too large.

I've not done such a thing, but I have had jobs where i needed to produce a fairly long thread which exceeded the guide bushings land where the max major diameter was slightly smaller than the materials od, and I had no problems with it, I just made sure every pass but the final did not skim the crest of the thread so I was rigid. Different application but a similar circumstance.

I cant imagine you having any problems as long as you take it easy, and perhaps even support the part with the sub when you are milling the flat etc. One thing I could think of is if the pitch is so large that your cutoff can fit inbetween crests you could maybe have some issues if it just happens to bite the right way, but I dont have any experience with this off hand I just think its always good to think of potential issues.

Glen