Thread Rolling CNC Turret Lathe

[Rick Finsta]

The Kennametal/Erickson thread roller attachment just caught my eye. I was handed some shaft work this week and had to work around a 0.007" taper from thread start to thread end on both ends. I know this is a part that could be much more economical to have done at a place with thread rolling machines, but it is short run stuff so who knows.

Part was 8.5" long 0.500" OD stainless round bar of unknown grade, but cut more like 316 than 304 and was nonmagnetic so I doubt it was 416. Each end had a 2.25" long thread, one side 1/2"x13 and the other 1/2"x20. I didn't have time to switch the barfeeder over so we saw cut blanks and hand fed to a turret stop, threaded one end, then flipped for the other side.

Are there any tools that will go into a boring bar holder on a turret lathe and allow threads like this to be rolled instead of cut? If this was 304 I bet I would have been chasing the deflection number constantly. Or would something like a geometric threading tool take care of this? I've never used one of those, either.

 

[Vancbiker]

Back in the 70s when I started working in a machine shop we had a handful of W&S turret lathes, each with a couple Landis thread rolling heads and Geometric thread cutting heads. Your job sounds perfect for either one of those tools.

We made lots of rolled thread studs from HT 4140 rod. 2" long 1"-12 threads on each end with about 3" of relief in the middle. Feed the stock out and cut the relief, then feed again to length and plunge chamfer. Roll threads on first end then move across the relief and roll the next. When the rolls got to the chamfer the roller pulled off and opened. Retract the turret back and part off the finished stud.

Do a couple hundred of those a day and you went home a pretty tired young man.

To do your parts similarly would require two heads.

 

[Rick Finsta]

Thanks, they used to do stuff like this on a Warner-Swasey (Spelling?) but that is dedicated to a single product nowadays. We got rid of all our other screw machines and turret lathe when we moved all the legacy work from them to a CNC swiss. I'll dig around and see if we sent all the geometric thread tooling to the scrap truck.

 

[Ox]

At first read - I took it that you were to intentionally put a .007 taper on your thread.
Like it was s'posed to tighten up into the mating part.

But maybe that is not what you meant?

I have no experience with Landis products, and know them mostly as a stand-alone type machine name.
Not so much for attachments.
I wouldn't be looking for that name brand in 2019.
I would not want to try to cut 304 with Geometric at all! (or NAMCO)

A Fette or NAMCO model 1 or 2 end working head would work good.
Need to check what helix will doo either pitch.
One head may or may not run both of those threads.

One catch with those is that you normally need to reset those by hand each cycle, unless you get an auto style unit that uses a bronze yoke to open/close.
Those get to be a long set-up tho, and don't lend themselves all that much better to a single spindle CNC lathe.

The Manuel close units can be made to close on index if you mount a pc of UHMW or some such somewhere on the machine superstructure, and index past it in a mannor that will close the head. It will make some noise, but ....


If you WANT to put on the .007 taper, you doo NOT want to use an endwerking head at all, and then need to come in from the cross slide with a completely different attachment.


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Think Snow Eh!
Ox

 

[DDoug]

Landis Home - Landis

 

[Ox]

Landis Home - Landis

Yeah, they were advertising that EZ-Roller when it first came out.
Those would save you from having to go buy a whole head for one thread, but they don't look to be all that economical beyond that.
???

Would need to check for sure.

I've never heard from anyone that has used them so far.



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Think Snow Eh!
Ox

 

[DDoug]

Yeah, they were advertising that EZ-Roller when it first came out.
Those would save you from having to go buy a whole head for one thread, but they don't look to be all that economical beyond that.
???

Would need to check for sure.

I've never heard from anyone that has used them so far.



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Think Snow Eh!
Ox

Huh ?
I just dropped the linky to the company, they have self openers too.

 

[Vancbiker]

Huh ?
I just dropped the linky to the company, they have self openers too.

The ones I used were self-opening. They may well have dated back to WW2 as that was the vintage of the machines they were used on. The ones in the link from digger doug look exactly what I recall the ones I used looked like.

Never used a Geometric on stainless. Cut a lot of threads for ag equipment wheel spindles that were pre-hardened 4140 or 4340 and they worked fine. Smoke from the cutting oil probably shaved several years off my life tho..

 

[Rick Finsta]

Ox, the deflection resulting from the long stickout was causing the thread to cut as a taper, so I cut an opposite and equal taper in the program to have no net taper.

That alone wouldn't be too bad but if we had to make any large number of these the cycle time would suck with the small depth of cut to avoid even more deflection. Any more than 0.005" per pass and I was getting visible chatter marks in the threads, and I had to run a spring pass after every change in X or the chatter would show up.

 

[Ox]

OK, so this doesn't hep you on Part 1, but you could pull out with the sub and then thread your part by the front collet.
Then part off after both threaded.
That would help your deflection, but if it's a swiss, I've had issues with threading chips wrapping up in 304, and muckin' up the works when it pulled back into the bushing.

Maybe you can thread from rear turret in stead?



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Think Snow Eh!
Ox