Can't Find Thread Milling Accessory Thread

[adh2000]

A few years ago I recall someone discussing, with pics, a milling machine accessory that allowed you to do thread milling on a manual mill. It was a rotary table looking thing but as you cranked the table around it sort of unscrewed and moved up. I don't know how different pitches were done, I suppose some sort of gearing had to be changed out. I think the device may have dated from the 1960s or even earlier. Not overly popular I guess but I have an application now where something like that might work. Does anyone know what I am talking about or the name of this device?

 

[sfriedberg]

I recall that thread, but cannot locate it myself at the moment. I'll do a bit more hunting as time allows.

If memory serves (it might not!), there were multiple (fixed) helix guides to control the vertical advance. No gear ratios involved. Sort of like helix angle on a Fellows gear shaper.

 

[Yan_b]

ROTARY TABLE - Vetcoa 6, Rotary Thread Mill 12" Table | eBay

 

[adh2000]

That's it! Thanks a million. The previous threads all died pretty quickly. Anyone ever actually used one of these?

 

[Brian@VersaMil]

I have one and used it in the past. It does require a leadscrew for every pitch of thread you need to mill. For certain size of parts, it's an effective tool, but once a person gets into cnc's this table loses it's appeal. They may advertise it as being effective with a Bridgeport mill, but the biggest problem is you run out of daylight under your spindle so quickly when you stack a rotary table on the mill, a cutter in the spindle and then the part you're trying to thread mill. Pretty much forces a person to put a riser on the Bridgeport to get enough room to use this tool. By the time I had my Sip jig bores, with FOUR FEET of daylight, I'd already gone to CNC milling of threads.

My Vetcoa has been sitting on a shelf for over ten years! For certain parts however, it IS a viable and fairly simple way to machine threads.

 

[wesg]

I seem to recall a post by some 'kid' that had figured out a way to do it without one of these. I'm a complete blank on how, but I remember thinking it was damn clever.

 

[adh2000]

I have one and used it in the past. It does require a leadscrew for every pitch of thread you need to mill. For certain size of parts, it's an effective tool, but once a person gets into cnc's this table loses it's appeal. They may advertise it as being effective with a Bridgeport mill, but the biggest problem is you run out of daylight under your spindle so quickly when you stack a rotary table on the mill, a cutter in the spindle and then the part you're trying to thread mill. Pretty much forces a person to put a riser on the Bridgeport to get enough room to use this tool. By the time I had my Sip jig bores, with FOUR FEET of daylight, I'd already gone to CNC milling of threads.

My Vetcoa has been sitting on a shelf for over ten years! For certain parts however, it IS a viable and fairly simple way to machine threads.

Thanks for this. If you don't mind sharing more on the use, it seems it might be difficult to set up. Did you mill the thread in one pass? Seems like you'd like to, but how would you get the pitch diameter right on? Seems you'd have to creep up on it, each time checking with a plug gauge. What a pain especially with limited head room as you point out.

Can you retract the tool without moving the unit so that the cutting tool is off the work? I guess that would require zero back lash, but wondering about that.

Looks like the lead screws are steel and the nuts bronze. Did you make any yourself? Square thread?

Thanks.

 

[Brian@VersaMil]

Yes the thread was milled in one pass. At first with a three tooth thread mill- all the teeth in line, which meant my part had to rotate enough times to get the
thread length correct. But later I got a Kennametal thread milling tool that had eight to ten teeth using an insert. This one would cut the entire thread in ONE revolution, with the rotary table feeding up one thread pitch. ALL of my parts used 16TPI so I didn't have to worry about not having the right leadscrew.

Setting up for milling was not too hard, but with the Vetcoa in it's fully lowered position at 7 3/4 inches, and my parts either being six inches or EIGHT inches, I was really out of room. Even with an Indicol for finding center it was tight. Since I was running the same parts I could make a plug to go in the center hole of the Vetcoa, to line up my part. Getting thread depth wasn't hard. Find the position where the cutter just touches the surface, zero out the DRO and then move over the depth of thread. Do a couple of parts and you're off to the races. My mating parts for the threads, a bearing retainer, were so thin I could use one to check threads without moving anything. After my thread was cut I would move the table over to clear the cutter. Nothing to it. If you weren't deep enough you DO have to allow the Vetcoa to lower, and NOT move the spindle of your machine, or you will lose the lead. The Vetcao is a DC drive machine, and I would bet you could pick up your lead if you were careful however.

I was running my castings on an Excello double end boring machine for the bearing journals and thread ID's and then thread milling. Didn't take very long to realize it's faster and easier to thread these in my CNC lathe after making arbors to match my casting, and the Vetcoa was put away forever. It DID work, it's a VERY nicely made machine. If I didn't have CNC capablities, for certain applications, it's a great tool. I BOUGHT a riser for my Bridgeport, but changed my process before I installed it. If you have parts MORE than eight inches high, figure on a riser or another way to do your threads.

Leadscrews are a VEE thread, I never had to make any.

 

[adh2000]

Thanks for that write up. CNC or not once you have the part on a mandrel on a lathe you're good to thread. Alas CNC is not on my radar. I have a lot of one or two off random castings that need large diameter threaded holes, some close to the edge so that mounting and balancing on a lathe face plate is a pain.

I'm thinking with the Vetcoa it would be easier to fixture. It would be a single pass, possibly a single revolution (thanks for that cool idea) and it would be easier to thread to the bottom of a blind hole. From your description it sounds like these are all good assumptions. I would need 4 or 5 leadscrews. I guess the last question would be: Do you want to sell your Vetcoa?

 

[Zahnrad Kopf]

Alas CNC is not on my radar.

So... you don’t know anyone with a machining center or two that can fit your castings...?

 

[adh2000]

Are you volunteering? I tried a couple places but they wouldn't run cast iron. Most people aren't going to want to screw with this, I'm sort of a do it yourself that way it won't be screwed up kind of guy.

 

[Zahnrad Kopf]

Are you volunteering? I tried a couple places but they wouldn't run cast iron. Most people aren't going to want to screw with this, I'm sort of a do it yourself that way it won't be screwed up kind of guy.

Veterans know better than to volunteer for anything that doesn't bring fortune, fame, or glory. But I might be inclined to assist an acquaintance in need if it didn't overly interfere with work flow.


Lucky for you we just got done running a bunch of CI, so the table is open and the machine still needs cleanup...

Even did some thread milling, too... The tool might even still be in the magazine...

Shoot me an e* with the details of what you need. Or not. I understand one wanting to do things for one's self.

 

[Zahnrad Kopf]

Waited as long as I could. Machine is cleaned up, vices back on the table, running more work.

 

[Mebfab]

Problem with the vetcoa,

Out of business (at least I couldnt find them) and leadscrews are rare. Anyone have any?

 

[rickseeman]

Is there a gizmo such as this that can thread grind? I have some inconel alloy bolts and some titanium bolts that I would like to thread but don't know how. I don't think my Leblond will thread inconel alloy bolts.

 

[adh2000]

After a year and a half of searching a Vetcoa finally turned up at a local auction. Amazingly I had some competition on it but got it for $200 with 5 lead screws. Came with 5, 6, 7, 8, and 18 TPI lead screws. Not the most useful pitches. I need 16, 20, and 24. Before I get to making them maybe someone, Brian perhaps, would want to sell me his table and screws. Assuming I make them what is the recommended bronze alloy?

 

[johnoder]

Assuming I make them what is the recommended bronze alloy?

C936 would machine like butter
C954 would last forever, lots tougher to machine
C932 is the less free machining version of C936

 

[sfriedberg]

I had some competition on it but got it for $200 with 5 lead screws.

Awesome deal if you have the use for it!

 

[Brian@VersaMil]

A rare day for me to look at PM- interesting to see an older thread resurrected. I still have the Vetcoa on the same shelf as when I posted. Don't think I'd sell it for 200 bucks however. I don't remember what pitch screws I have for it. I KNOW I have a 16TPI. I am thinking of retiring so everything will be leaving at some point, but enough stuff left to keep me entertained until I start drooling. Congrats on finding one. They are pretty rare.