Collet confusion.

In article , "Kevin(Bluey)" writes

The great advantage of ER collets is that their double taper means they can close down by 1.0mm (0.5 for the very small sizes) and still maintain excellent grip and concentricity. Collets with a single taper will only work efficiently for material of the exact diameter of the collet; even normal mild steel (usually a few thou under nominal) can be a problem with single taper collets.

This means that a set of ER collets will grip anything within their range - you don't need a metric set and an imperial set, for instance. They will grip milling cutters effectively. The collets themselves do not need a drawbar as the double taper holds them in; it is the collet chuck itself that needs a drawbar, at least when holding milling cutters.

The different numbers are just sizes. ER25 (the set I use) goes from 1.0 to 16.0 mm; the larger sets have a correspondingly larger range.

David

David , Thanks for clearing that up . I thought it was some evil conspiricy to extract more folding green from our pockets by having to buy a set of each because of some manufactured difference.

In article , "Kevin(Bluey)" writes

Just to make sure there is no confusion, I should explain that the different sets are different in size. They are not interchangeable between sets. I think it would be unfair to say this is done to extract more money, just that there is a set appropriate for your equipment. Thus, for my lathe (S7) and milling machine (Emco FB2) the ER25 size is about right; the holders for the larger sets would be inconveniently large for the 2MT spindle. The "25" in ER25 refers, I think, to the widest part of the chuck taper, the actual collets are about 26mm at their widest point.

Don't let the profusion put you off, just find the right size for your machinery and buy a set, you will find them invaluable.

See, for example:

David

All clear and understood.

I had that link bookmarked , and will check it out again.

Not sure I'll buy a set just yet ,I still have the Myford collet set ,But these below would be able to fit my drill press and a future mill with the MT 2 chuck. I have some other tooling I want to get first

Found this set on the Bay ,price is good ,not sure on the quality , made in the Peoples Republic of C .

Thanks again

In article , "Kevin(Bluey)" writes

Well the price is certainly attractive. Some of the cheaper sets have been reported to have slightly higher run-out (lack of concentricity) than they should, but for the holders at least it is possible to clean them up in the lathe you will be using it on (see correspondence here a few months ago). Not much you can do if the collets are out of true. Try looking at the seller's feedback to see if anyone has complained, or asking around.

David

AET stuff is nice, but for ER25 collets

(satisfied customer only)

-- Peter Fairbrother

I'm not sure that it's the double taper so much as the fact that there are eight gripping segments, rather than three in a normal collet.

In a three-segement collet the inside of the segments is round, and if it is used to grip a tool which is slightly smaller than the hole then each segment will only touch the tool on a thin line.

With eight (or perhaps sixteen) segments an ER collet will grip on 8 or

Also, as there are 8/16 gaps, they can close up more than i=f there are three gaps.

-- Peter Fairbrother

Missed this post.

The cheap ones can be pretty good, I bought an ER25 set all of which have a TIR within a single 1/100 mm division on a normal dial gauge.

Which is pretty darn good.

YMMV,

-- Peter Fairbrother

The eight slits help improve grip, of course, but I believe it is the double taper and the fact that the slits are alternately from front and back. This means that on closing down the collet grips the work or cutter at front and back (indeed probably all the way along) instead of just at the front. Some text books even show this diagrammatically.

David

David , Thank you for your in informative explaination ,its has been most helpful. This news group is one of the best on usenet , and the people friendly and helpful.

Yes, it's most helpful having the contact surfaces go all along the length (rather than squeezing one end of the tool shaft at the point where it leaves the collet, and leaving the other end inside the collet wobbling about).

This happens because the inside of an ER collet remains parallel to the tool when compressed, because the main taper acts along all the length of the collet. Move the collet in a bit and both ends move in, rather than just one.

A collet with a single taper would do this too.

I'm not sure what the second, front taper on an ER collet does? Makes the front end grip hardest? angles the compressive force properly?

Anyone?

-- Peter Fairbrother

Some text books even show this diagrammatically.

You read the instructions?

In article , Peter Fairbrother writes

It may be that it allows easy changing of collets from the front without need for a drawbar (apart from the one on the collet chuck, of course). But I think the front taper, as you say, improves the grip at the front.

Well, more that I just noticed it somewhere. Actually, there is a little subtlety in loading an ER collet into the closing nut, so RTFM is not a bad idea in this case.

David

hello Kevin, just one thing to point out - although each closes down by up to 1mm - it a good idea at the outset to decide if you are 'imperial or metric' - it isn't true to say that a set will hold all cutting tools within the range of the set. If you look at the link below, you will see that the 14mm collet will close down to 13mm, but the next one down is a 12mm collet - so there isn't a collet to hold a 1/2" tool - ditto 1/4". So you might need to buy extra collets to fill in - or go one way or the other from the start!

Hugh

Correct for the "part" set that you provided a link for but the normal "full" set for ER32 includes 18 collets and does cover the full range and the ER 25 full set includes 15 collets and does likewise.

Regards

Keith

from "Hugh"

It will cause confusion in-as-much-as the information is incorrect (I'm sure many others on the group will also reply). ER collets are made to cover the complete range of potential capacity. In the case of ER32 that is 2mm to 20mm.

The eBay item cited is a set of 12 whereas the complete range would be a set of 21.

JG

Henry

Dammit! That must mean that my 13mm-12mm ER32 must have been incorrectly laser marked then , as it grips 1/2" perfectly.

One point worth mentioning, although each collet has a full 1mm range, they have more gripping power close to the larger end of the size than the smaller end. There is information relating to this somewhere on the Rego-Fix site.

Peter

Given that I've go 65 imperial 5C collets and 25 metric ones and would still struggle with off sizes, one could stump up for a set of half sizes and still be ahead of the game (if anyone sold them)

Mark Rand RTFM

I was scratching my head wondering how you were using 5Cs on a Myford, then I remembered that you bought a CVA didn't you?

Peter