Wire edm'ing 5C collet for 3/4 stainless steel tubing

I will have about 3000 ( more in the futur) of these 3/4 stainless steel tube to machine, inside and outside.

My problem is that tubes are not seemless tubes so they are not really 3/4 but kind of an egg shape, maybe 0.746 for the smallest dimension and 0.753 for the bigger dimension.

My question is, can I buy a couple of 0.625 5C collets and have them wire edm to the shape of the tube?

They will be machined on a small CNC lathe with bar feeder.

Thanks for any help, Jeff

Won't the tube deform to round when the collet closes?

ostie01 said:

I will have about 3000 ( more in the futur) of these 3/4 stainless steel tube to machine, inside and outside.

My problem is that tubes are not seemless tubes so they are not really 3/4 but kind of an egg shape, maybe 0.746 for the smallest dimension and 0.753 for the bigger dimension.

My question is, can I buy a couple of 0.625 5C collets and have them wire edm to the shape of the tube?

They will be machined on a small CNC lathe with bar feeder.

Thanks for any help, Jeff

Click to expand...

How thick is the wall on that tubing?

If not too thick, I suspect a 2J collet could MAKE the + / - three thou go to proper round for the section of it in the grip zone.

5C, mebbe not, but even so, it might be cheaper to wear-out a passel of rather ordinary 5C than to make custom ones for so small a deviation, coz one might not be enough, even so.

"Day Job" usta shop-fab 3C and 5C for that sort of imperfectly round. Rod stock, not tubing, and very much smaller diameter - under 1/4", even under 1/8", usually.

Brass collet instead of steel sometimes, but shop-fab rather than store-bought 'emergency' so we could split them to four or even six-way 'petals' rather than just three. Straight bore, just more flex points.

Got the job done, were 'expendables' even when we bothered to carefully heat-treat them to a decent springiness. EG: Not always.

Might try that trick, too, to get your grip. Should be able to slice stock collets at normal hardness with something 'modern' and coolant enough they do not overheat and draw spring temper.

ADFToolmaker said:

Won't the tube deform to round when the collet closes?

Click to expand...

Not sure about wall thickness, I know that the finish inside dimension is
0.623 +.0015 and -0.000.

I don't think the tube would deform as the clamping pressure of a 5C collet is not enough and 5C collet won't allow dimension over 0.750, at least not the ones I tried.

Jeff

ostie01 said:

Not sure about wall thickness, I know that the finish inside dimension is
0.623 +.0015 and -0.000.

I don't think the tube would deform as the clamping pressure of a 5C collet is not enough and 5C collet won't allow dimension over 0.750, at least not the ones I tried.

Jeff

Click to expand...

An Ortleib Quadra that can use current-production rubberflex as well as steel pad and steel sub spring-collet would be serious spendy, but if it fit your spindle, might make lots of work easier.

Power operated, of course, so it plays well with CNC cycle times.

Among the several advantages it could bring is ability to hold a matched pair of rubberflex, back-to-back, reversed taper-cone direction.

That gives you extra grip against push-back - rather a LOT of it, compared to even a perfectly fitted 5C - and whether the tubing deforms to better roundness or not. or remains at a no-longer critical matching 'clock' position.

I have 'manual' Rubberflex but would not tackle 3,000 piece runs with it unless I also got to magically be 20 years old again as part of the deal.

Good TIR, forgiving fit, good grip, but RPITA to open and close.



BTW .. you've cited:

.. maybe 0.746 for the smallest dimension and 0.753 for the bigger dimension.

Click to expand...

As it HAS that variance, I'd expect variance within variance, so with any 'spring' collet, you'll have to align the stock by hand and/or metrology, hope it stays within range of your custom 5C, self-aligns as the feeder cycles.

Trust that to a three-leaf 5C? I do not.

You can appreciate why I'd assign my Rubberflex or Burnerd Multisize to this sort of tasking, as neither of them gives a damn about that mere nuisance-level variance.

Shorter life of more 5C segments and less concern as to how the stock feeds might be more sustainable, overall.

Turn a 3-lobe into a 6-lobe, suck it and see. You'll have an answer faster than you can get a custom grind or EDM done.

JM2CW

3 jaw chuck with soft jaws bored to near enough a full circle ?

Limy Sami said:

3 jaw chuck with soft jaws bored to near enough a full circle ?

Click to expand...

Powered TWO-jaw would be my pref for CNC throughputs.

Mine is a Hardinge manual one. No powered workholding OR CNC'ed gear under my roof, but retired ain't quite the same as 'virgin', so...

Hi ostie01:
Sure a 5C collet can be wire cut to suit your tubes.
I do this all the time for odd shapes on my 5C chucker.
The thing you need to determine is if you want the bores you turn to be round when the tube is unclamped.
If so you make the collet the same shape as the unclamped tube.
If the tube will be forced round in use , then you want a round collet in which case you can just bore a pot collet or emergency collet to a diameter that will allow you to get the tube in and clamp it.
Any wire shop can do this; it's nothing special.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com

What Marcus said...

You might check into the cost of centerless grinding the whole bars. We had a problem with bars slipping in collets and we sent them out to a company called long bar grinding in Santa Fe Springs California . The bars were 12 ft long and after grinding we had no more problems. I am sure there are more grinders out there doing the same.
Jimsehr