ER Collet Sizes

Hi I'm new to ER collets and have just bought one marked as 6-5 which I assume should cover the range 6mm to 5mm. However while a 6mm silver steel rod fits ok when the collet is out of the nut, it is an extremely tight fit when mounted in the nut, so much so that I worry that trying to get a 2mm rod in a 2mm collet would be near impossible without bending the rod. My question is, should these collets cover the complete range quoted eg 6mm to 5mm, or does the range mean 'slightly less than 6mm down to 5mm', in which case a 6mm rod would be a better fit in a 7mm to 6mm collet? Would the alternative of using a 1/4" collet (if such were available) when the 6mm rod would be in the middle of the range be a better solution?

Any thoughts?

Pat

Reply to
Patrick
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It should hold a 6mm rod fine but there are differences in the nuts being supplied with some of the chucks / adaptors that cause the collet to be held undersize. Can you borrow another collet nut from a different source / friend etc to check this ?

There are rumored to be some imperial collets where say 1/4" is the top end but I have never seen them. All the imperial collets I have bought still come marked 5-6, just differently priced ?

-- Regards,

John Stevenson Nottingham, England.

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Reply to
John Stevenson

You don't say which ER size ;) Both the ER16 and ER25 sets I have fit fairly loose in the nut, so I would not expect a difference unless your '6mm' bar is a little over size already. A 6mm drill should fit in or out of the nut, but a 6.1mm would be tight, if it fits at all, which would depend on the flexibility of the collet.

Reply to
Lester Caine
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Can you be more specific John? ie. are nuts from ArcEuro better than those from (say) Cronos or whomever?

I'm considering making a chuck body but buying in the nut and your answer could affect my decission!

JG

Reply to
JG

All the ones I've used work exactly to their quoted range, right down to

1mm.

Bear in mind that you need to put material of same diameter all the way through the collet. You can sometimes bodge a short piece into the collet by putting a matching short bit of scrap in the other end.

- Nigel

Reply to
Nigel Cliffe

It is an ER16 collet and nut from Arc Euro. I have measured the rod as

5.95mm.

Pat

Reply to
Patrick

Well my ER16 collets are from Arc Euro, but the nut is on the Taig spindle. I will have a look when I get a chance, but I'm not finding a problem so perhaps the Arc Euro nut has a little less 'room' :( I'm running 6mm tools into the spindle with no tightness ;)

Reply to
Lester Caine

As my other post, the rod I used measures 5.95mm and is longer (actally about 100mm) than the collet. With the collet out of the nut the fit is loose, with the collet in the nut the fit is almost impossible.

Pat

Reply to
Patrick

Pat

......and you sure that you are fitting the internal lug on the nut into the annular recess on the front of the collet? (Well, *somebody* has to ask!) --

Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

Reply to
Chris Edwards

I am often quite stupid but not often quite that stupid.

Pat (in deepest Dorset!)

Reply to
Patrick

Nigel,

I found that out last week when I tried to grip a short stub of 3/32" in the appropriate ER25 collett. I finished up using a Myford 2MT collet which did the job.

Jim.

Reply to
Jim Guthrie

No, it means 6mm downto mm. A 6mm rod should need a bit of force to go in. But not a hammer. If you have problems getting the rod in, the collet might have fallen down onto the floor and slightly bent. If things change with the nut, get a new nut. Recently, I bought a new collet nut and I had to return it, because it was too tight.

Nick

Reply to
Nick Mueller

WHAT!? :-))

Nick

Reply to
Nick Mueller

at:-

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Interestingly (well I thought it was interesting anyway..) My set of vertex ER-16 collets are dual marked, though only the metric is a range, eg the 6mm is marked 6-5 and 7/32" and the 7mm is marked 7-6 and 1/4", guess there are no true imperial ER collets.

Dave

Reply to
dave sanderson

In article , Patrick writes

Pat,

While I would not disagree with the previous comments, it is worth adding that I have often noticed that my ER25 collets start to tighten at the lightest screwing-in of the closing nut. Thus if I fit the collet and screw on the nut to the point where I didn't think it was closing, it actually is, a little, and material of the largest nominal size will not go in (or only goes in with difficulty). Unscrewing the closing nut a little - not enough to have it fall off, of course! - will allow the material to go in.

David

Reply to
David Littlewood

The Collet nut came from Arc Euro. I contacted them and Ketan kindly went through his stock and picked out and sent me another nut. This one is much better and 6mm rod slips into a 6mm-5mm collet quite easily, although it's obvious that you couldn't go much larger than 6mm.

I consider that to be extremely good service from Arc Euro but it does show that these nuts do vary is size, possibly very slightly but enough to make life difficult.

I bought the nut because I wanted to fabricated a collet chuck (ER16) on the lathe it will be used on.

The taper was cut at 8 degrees by setting the cross-slide over to produce a

2.78mm deflection in 20mm slide movement, which should correspond to 8 degrees. The taper run-out was measured at effectively zero, which is as expected.

The collets I have are 6-5mm, 5-4mm and 2.5-1.5mm. Covering the range of each with drill rod eg 6mm, 5.5mm and 5mm, I measured run-out of the rods. In all cases I am getting in the region of 0.02mm to 0.04mm run-out.

My question is - is this expected for inexpensive collets not sold as 'precision' items and with no quoted accuracy figure?

Please note that I have been careful to not make 'silly mistakes' ie keeping everything clean, fitting the collets into the chuck correctly and fitting the rods into the collets correctly etc.

Pat

Reply to
Patrick

Too late now, but here is a simple and precise way: Turn down some rod that is a tad over the nominal size of a (the biggest) collet. Slip the collet over it. Now, with a dial indicator on the compound adjust it to read zero if you traverse the collet with the dial indicator.

Nick

Reply to
Nick Mueller

Yes, I did precisely that initially and had problems with run-out. I thought setting to 8 degrees may be a more accurate way of doing it.

Pat

Reply to
Patrick

Thanks for that tip Nick.

Obvious when you think about it but coming to that conclusion from first principles is what separates the men from the boys :)

JG

Reply to
JG

Oh, there is one "small" trick to pay attention to: That rod has to be dead cylindrical. If you can't get that, make a recess in the middle and turn the two precise lands to the same diameter. If you can't do that, put some ground bar into the chuck. But then you have to measure 180° apart (rotate 180°) and use the average.

Pay attention that your dial-indicator is a center-height, or you get distortions (different radii).

Nick

Reply to
Nick Mueller

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