ID workholding for small, long bore in sub side of Swiss turn center

thunderskunk · Oct 15, 2021

That title was a mouthful…

We make copper parts with an ID feature. Currently, ID feature is made on subside in collet, which has its… hiccups. But we do stupid high volume, and it works.

Is there a common provider for ID workholding? Bore is .275-.325 ish, and is 1.5”+ deep. Features usually need to be held to .005” for runout, but typically we’re looking at all OD features including datum.

Nerdlinger · Oct 16, 2021

So you want to hold the part on the .275-.325ish ID so you can work on the OD in the sub?

thunderskunk · Oct 16, 2021

Nerdlinger said:
So you want to hold the part on the .275-.325ish ID so you can work on the OD in the sub?

Yes. Main side does ID work, rough turn, and back end features, sub side does front end flats, blind hole, finish turn, and o-rings. Maybe… honestly having a tough time conceptualizing it myself, as there’s pros and cons to either direction.

Mechanola · Oct 16, 2021

What lathe do you have? Tornos offers them, Citizen, others.

The point is that the earlier you can make an inner cylinder to clamp on the better you will be off. Turn ID and one side, then move over to do the rest.

EmGo · Oct 16, 2021

thunderskunk said:
Is there a common provider for ID workholding?

I think LeCount had the original patent on hydraulic expanding mandrels. Positrol, and there were a few others in the Detroit area making them. Five thou is nothing, most of those hold a couple tenths. Five sixteenths is pretty small tho, that might be a problem, I never got anything that dinky.

thunderskunk · Oct 17, 2021

Mechanola said:
What lathe do you have? Tornos offers them, Citizen, others.

Citizen L20’s, several different generations. Mixed bag of barfeeders.

TeachMePlease · Oct 18, 2021

Just get any of the major brands to make you an extended nose sub collet with a step on the face the diameter of the ID, close the sub collet, insert it into the part, open the sub collet, you've got an ID chucking sub collet.

wmpy · Oct 18, 2021

TeachMePlease said:
Just get any of the major brands to make you an extended nose sub collet with a step on the face the diameter of the ID, close the sub collet, insert it into the part, open the sub collet, you've got an ID chucking sub collet.

Is this really something that's done? Unless you have a different clamping mechanism than I'm used to seeing on a Swiss machine, won't you only have the spring tension of the collet providing the gripping force on the part? It seems to me that it wouldn't hold the part strong enough to do any type of machining.

TeachMePlease · Oct 19, 2021

wmpy said:
Is this really something that's done? Unless you have a different clamping mechanism than I'm used to seeing on a Swiss machine, won't you only have the spring tension of the collet providing the gripping force on the part? It seems to me that it wouldn't hold the part strong enough to do any type of machining.

It is indeed something that's done. Generally only for fairly light secondary finishing ops, the milling would have to be fairly light, but I have indeed seen it applied in special cases with no issue.

The 2nd option that I can think of is to make yourself a custom ID mandrel that's fed with high pressure coolant (on my machines that's up to 1000 PSI) that can slip inside the part and be expanded with 1000 PSI to provide gripping force. But it'd take me some trial and error to design such an item.

thunderskunk · Oct 20, 2021

We use servo collets. It may still be a spring, but pressure is a lot more adjustable.

Having more trouble than I thought, but I’ve found a few possibles at a trade show.

TeachMePlease · Oct 20, 2021

thunderskunk said:
We use servo collets. It may still be a spring, but pressure is a lot more adjustable.

Having more trouble than I thought, but I’ve found a few possibles at a trade show.

Please share, in case any of us are in a similar quandary in the future!

EmGo · Oct 20, 2021

TeachMePlease said:
The 2nd option that I can think of is to make yourself a custom ID mandrel that's fed with high pressure coolant (on my machines that's up to 1000 PSI) that can slip inside the part and be expanded with 1000 PSI to provide gripping force. But it'd take me some trial and error to design such an item.

There are places that do this, but they mostly don't use machine coolant. They are filled with a hydraulic oil or grease in a closed cavity, you slide the part on then tighten a plug in the oil cavity which expands a sleeve and grips the part. Wish I could remember some names, they are commonly used for gripping internally splined parts, so you can turn the o.d. concentric with the spline. Also used for other stuff but that's where I came across them.

Internet search is just about useless these days, all it turns up is some amazon shit

wmpy · Oct 20, 2021

thunderskunk said:
We use servo collets. It may still be a spring, but pressure is a lot more adjustable.

Having more trouble than I thought, but I’ve found a few possibles at a trade show.

What are servo collets?

Maybe you've already seen these...
https://www.floydautomatic.co.uk/products.php?cat=208
If you can't find a dealer in the US, Floyd will ship here.

Nerdlinger · Oct 21, 2021

My machines have a dual acting pneumatic cylinder for use with an ejector pin….if yours has that you might be able to make an ejector pin that has a taper on it that could spread apart your tiny little ID collet with the “retract” pressure? You probably wouldn’t get much travel on the piston so you’d have to adjust your position sensors accordingly (assuming yours has them.).

Any chance you want to throw up a print (or sketch?) so we can look at it?

Good luck!

thunderskunk · Oct 21, 2021

wmpy said:
What are servo collets?

Maybe you've already seen these...
https://www.floydautomatic.co.uk/products.php?cat=208
If you can't find a dealer in the US, Floyd will ship here.

I didn’t meet Floyd but I saw someone selling their stuff today. That’s exactly what I’m looking for, it just doesn’t come standard for a .300 ID.

EmGo · Oct 21, 2021

Brain finally came up with a name or two.

These guys are cool, and closer than england

Jerry Tools - Arbors

Their hydraulic nuts are spiffy. Website sucks balls.

Not sure if their automatic chucks go this small but the manual ones do, probably not what you want, but another choice

Special mandrels | TOBLER-WORKHOLDING

England, don't know if they go small enough

Acugrip - Hydraulic arbors & chucks

Useless website but I thought they had small expanders

Precision Arbors and Chucks from Hydra-Lock : Solid and Split Steel Expanding Sleeve

(Amazing how bad most websites are at actually showing product. Great about telling what their cat ate for breakfast, though)

thunderskunk · Jan 21, 2022

Just to follow up: iSwiss makes an arbor that fits right into a TF25 spindle; comes like an emergency collet so it needs to be turned down. Expensive little toy, but we’re giving it a shot.

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