What tolerance should you accept for a bought ER25 collet chuck?

[Metal Mickey]

Since refurbishing my Myford ML7 I have learnt not to trust tooling and now measure everything (including finding the toolpost on my nearly new tailstock out of true) so when a new ER25 collet chuck from a well know UK tool supplier I tested it for running true with a stainless steel bar in the collet.

It came out with a 0.008" variation. I thought at first it may be the bar but I started and put the dial indicator on the nose of the ML7, which was fine. I then tested the finished outside of the chuck itself and that was running true! SO I thought that I would test the inside of the chuck and it repeated the error (less a thou) found on the bar.

So if the outside of the chuck runs true and the inside doesn't to what I think is a significant and unacceptable amount (say 0.007" to be fair). Before I phone the supplier on Monday I thought I would ask members here for your views. Is that amount of runout acceptable or no. If no, what would be acceptable.

Many thanks. MM

 

[Bluechip]

Hi MM

I have a set of Vertex ER25 collets that run at > .001 TIR with an Arrand direct mounting chuck, ( not mine unfortunately ).

The same collets run at about .0015 in an Axminster 2MT chuck.

I had one chuck that ran about .005, direct Myford fixing, allegedly UK made. Crap. Gave it to a mate who sorted it.

Ask Arrand what they guarantee theirs to run at .. Expensive though, forget the price, sorry.

Some chucks are absolute Ess, Aitch One Tee.

IDIOT Should be < .001 : :

Dave

 

[Metal Mickey]

Thanks Dave, I will look forward to seeing other replies but your coments help to start making a judgement. Mike

 

[BobWarfield]

If you indicated the inside taper without a collet in the chuck, then you're on the right track to knowing what's wrong.

I had bad runout on one I thought, but it turned out to be the collet. I replaced it.

I have had good luck with all 3 of my ER32's. One is a no-name, and 2 are Bisons. I just bought an ER16 from Maritool.

I don't think I'd put up with one that wouldn't run 0.001" or better. The trouble is, if you use one to hold small endmills and it has more than that, it breaks the endmills. Think of that runout as a percentage of the endmill's diameter and you'll see how that happens. The poor thing just gets flailed about on small endmills.

Cheers,

BW

 

[Jasonb]

Worth checking with a few other collets just to eliminate any error with the collet nut which may be pulling the collet(s) out of true but unlikely

Heres a pdf of the vertex collet tolerances in mm so thats about 5/10ths thou

http://rotagriponline.com/datasheets/C01.pdf

Jason

 

[Bluechip]

MM

I've edited my post ... The Arrand chuck has LESS THAN .001" TIR

Need more beer ... Brain drying out, could be fatal ..

Dave

 

[Metal Mickey]

Thanks for the comments. I should have made it clearer, the inside runout is the taper part without any collets. This compares with the outside of the chuck itself (which runs true) so I am happy that the central taper part of the cuck is not concentric with its body.

I will contact the supplier tomorrow and ask for a replacement. I will let you know how I get on.

Heres a pdf of the vertex collet tolerances in mm so thats about 5/10ths thou

http://rotagriponline.com/datasheets/C01.pdf

Jason

Thanks Jason.

 

[djc]

...a new ER25 collet chuck... It came out with a 0.008" variation.

Presumably this is direct mounting on the spindle nose?

Have you checked the register diameter on the lathe and the register diameter on the chuck? Should be 1.250".

In answer to your question: you have to pay for quality.

If you want something you can dial in for minimal runout, buy one that mounts on a backplate, use slightly oversize mounting holes and 'adjust true' with a percussive device.

 

[rake60]

A .008" run out WOULD be considered "excessive" in some camps.
I'd want to investigate it further.
First I'd check the TIR (Total Indicated Runout) of the lathes spindle taper.
If it runs out that will be a condition you'll have to learn to live with.
No collet chuck can run any straighter than than the spindle taper.
If that taper is running concentric, mount the collet chuck and check it's
taper for run out. At the chuck taper the run out should not read more
than the spindle taper did.

Now when your actually machining, a run out in the machine will double
in a two end cutting operation. Chuck up a short piece of brass in the
collet. Center drill it and turn a length of it back far enough to be held
in the collet chuck. Flip it around chucking only on the pre-machined area
with the collet chuck and center drill that end and turn a length of it.

Put a dead center in the spindle and a dead or live center in the tail stock.
Set that test piece of brass between the two centers and check the
eccentricity of the turned portions with an indicator.
If the run out between the two is higher than .008 but not over .016"
you have a run out issue.
If it is less than that you have a set up problem.

But are any of those issues a problem at all?
The only time I use a collet chuck is for turning very small parts.
Those parts are machined complete in one set up and parted off the
parent material. If I'm making a .125" diameter part from 15.000" material
the collet could run out 14.875" and the part would clean up and and be
parted off as a perfectly round and concentric piece.

That's a hell of an exaggeration but I think it makes my point.
Accuracy in machining doesn't come out of a box.
Accuracy comes from the determination of a machine's operator.

Rick

 

[Metal Mickey]

Thanks for all the commments.

I used a dial indicator and tracked down the error to be the relationship between the ER25 inside taper and outside of the chuck. I phoned the UK supplier today and they are sending a replacement to me and are going to check the new one before sending it too me (according to the chap on the phone) so I will let you know.

The supplier didn't quibble over a replacement or even query my method of finding the error. I have since checked my other ER 25 chucks (I have 2, one on a MT2 and the other MT3). Both were bought from Singapore if memory serves me right. Neither shows any significant error and both were 'reasonable' prices, less than UK suppliers.

 

[BobWarfield]

I have seen this kind of error with several of my imported bits of tooling. For example, my 5C collet chuck has a beautiful ground finish outside, but the outside is nowhere near concentric with the taper. Fortunately in that case I was able to recut the mounting shoulder in a way that eliminated that error:

Always pays to think about how to machine based on how the thing will be used when making your own tooling.

Best,

BW

 

[steamer]

My Bison 5" 5C runs out less than a .0005".

Was this a Bison unit or of eastern decent?

Dave