ER25 v 5C Collets

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Conventional wisdom appears to be that ER Collets are better than 5C collets because they are more versatile.

5C collets are for specific sizes only.

However can anyone advise me if there is any difference in accuracy or concentricity between the two collet systems?

Edited By JasonB on 17/02/2019 07:14:09

Hi Adrian.

5C collets are available for Hex and square bar also, not so in ER
Also it is easy to make a nose piece and draw bar for the lathe. If you do a lot of precision bar work on longer lengths.

As seen here:
**LINK**

However ER is a little more stable holding cutters straight due to the longer gripping length. normally you cannot pass long work through an ER collet.

If the budget is tight I would consider ER first.

Cheers
John

John,

You can pass long work through an ER collet - provided the chuck is of the right type. The ones on a morse taper shank are (usually) solid, but the ones which screw on the spindle nose, or fit on a backplate, are (usually) capable of passing long work.

I have both types; the MT shank one is ideal for holding milling cutters in a milling machine, the others are ideal for use on a lathe.

I would certainly agree that the ER ones are more versatile (apart from the square/hex bit); I certainly use mine a lot more than the 5C ones.

David

Edited By David Littlewood on 08/05/2013 14:23:09

I understood that ER collets were originally designed for hold tooling, whereas 5C collets were intended for work holding. Of course there's nothing to stop you holding what you like in any variety of collet.

In theory I suspect that ER collets can be bought that are better than 5C collets. A quick 'google' found ER collets with TIRs of 0.0002" or better, whereas the best I found for 5C collets was 0.0004". However, none of the suppliers operate in the ME market. For the ME user I expect that where the collets are purchased from will have a far greater impact on accuracy and concentricity than any theoretical accuracy standards.

Regards,

Andrew

Edited By Andrew Johnston on 08/05/2013 14:40:30

hi David

Yes.... I should have been more specific. and I use 5c in the lathe and a little indexer as well. ER on the mill.

Cheers

John

I have never had any issues with using my 5C's they are excellent. The mounting of my 5C collet chuck has zero run out and I have Collets up to 1 1/4" (and28mm) in all the sizes that my drawings use. Whilst I have a ER32 holder I see no point in buying any collets to go with it as it is restricted to a much smaller maximum diameter than the 5C's.

I would recommend that you support long pieces of work which stick a long way out of any collet: It is not the inaccuracies of the collet that will be your problem but flex in the material as you machine it.

As for accuracy: The more you deviate from the standard collet size you will find that the collet is holding over less and less surface area as the bore of the collet is a specific size so effectively at the extreems it is holding on only three points, which is why it is possible to buy two standards of ER collets.

Cost wise I paid the same for a full 29 piece 32nd inch 5C's (up to 1" ) as you will pay for a 12 piece ER25 set (up to 5/8" ).

Jo

Edited By Jo on 08/05/2013 14:55:42

Add in the fact that 5C ( and 16C !) are available in "emergency" format to bore to required profile rhis allows a certain amount of flexabilty beyond ER

This may be so - but how many of us have machines which can actually take a 5C collet in its spindle?

David

You did ask; they're a bit small for both lathes and one of my mills, and too large for the other two mills. I use 5C collets on the 4th axis of the CNC mill.

Andrew

Thanks for the help gentlemen; I am a little closer to a decision.

The lathe has a 4MT spindle so I am committed to some form of chuck but I do appreciate that accuracy is only as good as the fitting of that chuck to a backplate.

All of my work is Imperial due to the inability of the Model Engineering world to move into the second half of the 20th century.

ER25 should work fine but very often the metric collet will be closed considerably and I do wonder if this can effect accuracy. e.g. 1/4 inch or 6.3 mm needs a 7mm collet.

Therefore I will probably go with 5C as most applications are on a fixed imperial size ground shaft.

regards

Adrian

Or 21st C

I'm not sure if I should apologise for re-opening an old post as many forum users seem to apologise for doing just this, but it seems better to me to keep related topics together - it makes searching for help so much simpler.

Anyhow.....some time ago I bought a threaded pull-through device from a local supplier for 5C collets (nothing to do with arceuro I'm happy to point out) to use in my lathe.This turned out to be an abortion of a thing, Slow to use when moving stock forward for the next item and prone to unscrewing in the wrong places.

I then read a forum post where it was suggested that a Stevenson's Collet block could be set up in a 4-jaw chuck and used as a collet chuck that was opened and closed from the front end of the lathe. This idea worked absolutely brilliantly for me. Fast and convenient.

Problem solved - except how can I hold square-section bar?

In another thread by the late,great, Earl of Bridgeport and Sumpwater he commented that Jason B had proved that an ER collet could be used to hold square and hexagonal stock, but I am unable to find that reference.

Alternatively is there a way of holding my existing 5C collets from the front of the chuck i.e. by compressing the front of the collet into a taper, in the same way that ER32 collets are closed?

Regards to all, Chas

Charles, you don't need the reference. ER collets have 4 slits from each end, offset by 45 degrees. You simply find a collet slightly bigger than your square bar and tighten it down so the corners fit in the slits. Maximum gripping length is rather less than the length of the collet since the slits can't go the full length (collet would fall apart).

You can probably hold hex too but it won't fit in the slits so may not be so accurate.

I doubt this is very good for the collets.

Charles why not just get a 5C chuck then all you need as a chuck key the same as a 3-jaw or 4-jaw and it's a one handed job. Less overhang than a block in a 4-jaw too. 

There are also 5C chucks that have a large handwheel an them to close the collet,

.

Yes I've held sq in an ER, will did out the pic later.

Edited By JasonB on 17/02/2019 07:34:18

I have both but prefer the 5c collets, I like my 5c collet chuck and the ability to hold short length that you cannot do in ER collets without a support piece. I wouldn't be without either system both have there own advantages.

about 70% of my lathe work is done in a 5C collet chuck

Unless there’s a particular reason I’d go for ER32 rather than ER25 as there are more fittings available for them. I use ER32 on my Lathe and Mill and use them with square and Hex collet blocks and with a spindexer. I often hold square stock in a collet. Agreed about closing down to 1/4” with a 7mm collet so I don’t do it! As well as a full set of metric collets I also have 1/8”, 1/4” 3/8” and 1/2”.

It actually works perfectly well with square, hex and octagonal