Collets

I fully realise this might open a can of worms, but what are the comparative benefits of selecting C5 collets over ER32s?

I realise that C5 collets are one size whereas the ER32 can close down 1mm to the size below the marked size.

So, bearing the above in mind, is there any appreciable (measurable) difference in workpiece holding or retention between the two standards?

Cheers, Barry

5C go larger upto 1 1/8", you can get square and hex ones, you can tighten the chuck with a tee shaped key rather than C spanner and means on stopping the spindle turning, 5C will take a backstop for repetative work. 5C adaptor will take your ER32 collets from your mill.

J

I have a variety of both C5 and ER32 tooling Barry.

All that Jason says above is correct and is an objective view. My (very subjective) view is a little more nuanced.

Generally I use ER32 to both hold work and tooling, which they do well within their limits - which I am unlikely to exceed I might add. I have a number of ER32 collet chucks - both back-plate mounted and on MT tapers and a full metric collet set (plus a few Imperial ones that are at the lower end of the metric 'closing' size). This generally suits my size of equipment (both lathes and mills) all of which have MT tapers ranging from MT1 to MT3 - although I use an ER32 back-plate mounted chuck for the MT1 lathe.

I also have a 5C spin indexer and the JS 5C 'blocks' plus some home made 5C holders. So generally my 5C bits are just used for work holding and indexing. I have a few accessories that I've made to be held in them (3 jaw chuck, small faceplate). I only have a few 5C collets but as these are generally for larger/awkward work holding - I don't need too many as I always have the JS ER32 '5C adaptor' as a get out of jail option..

This all might sound very complicated but was really a matter of workshop evolution. I started out with a simple 5C collet holder for the mill and then acquired the spin indexer - and I think this was all before 'ER' was generally affordable. At that time I was using MT tapered collet holders but when ER started to be more commonly available (at a price I wanted to pay) I decided to standardise on ER32.

If I was starting over - I would chose ER32 as my 'primary' work and tool holding system as it works well for the range of equipment I have and for the work that I do. However, I do believe that 5C is potentially the more robust (heavier duty) and more versatile system (particularly on larger machinery) and that for some (very occasional) applications it would still be my preferred choice.

So, without knowing the size of your equipment (or the work that you want to do with it) it is hard to say but for most "hobbyists" I think an ER based system would meet the majority of their needs.

Regards,

IanT

An oft overlooked disadvantage of ER collets is the substantial tightening torque needed to ensure that the grip and accuracy specifications are met. ER32 are supposed to be done up to 100 ft lb! Which is a lot and probably impossible with the usual sheet metal spanner supplied in Model Engineer affordable kits. Its also fairly risky in many Model Engineer sized machines which tend to have modest, but generally acceptable, spindle lock arrangements.

In practice less than book tightening torque is usually acceptable especially if your collet set matches the nominal dimensions of the materials and tools you use. Although nominal imperial and nominal metric sets will cover each others size range working in the non native system can involve use close to the extremes of the holding range where problems are more likely. Convenient and effective though the loose cap nut of the ER series is objectively its an imperfect system and due consideration is needed. Its important to ensure that the parallel gripping portion of an ER is filled. As ever one can successfully break the rules if you know what you are doing and think things through but get careless and you will end up in the kitty litter.

ER collets were designed for tool-holding and 5C for work-holding. Although both will do double duty the gremlin attack rate tends to be lower when used at their design task so its probably best to select on the basis of usual use.

I have a set of imperial ER 32 and 5C sets in 1 mm and 1/16 increments along with a couple of hexagon ones got for specific jobs. Also a spin indexer, vertical mount and a 3 jaw chuck on a 5C carrier. My lathe is also 5C native in the spindle. The ER collets get very little use and I'd not miss them if I didn't have them. For milling cutter holding I mostly use either a Clarkson type chuck or weldon style side screw holders. For me the ER set is a historical accident. It was a good idea at the time but the way my workshop evolved changed things. Having been bitten several times by the "good idea at the time but no longer right" bug I'd say only get an ER set if you are sure that is what you need. If unsure get the odd 5C and carriers as required accepting that if ER does turn out to be the way to go later you will probably need to get an ER to 5C adapter. Any surplus 5C collets are probably easier to sell too.

Clive

Barry,

I use both. ER25 in the mill and although I have an ER25 chuck for the lathe, I almost always use the 5C collet chuck. I find the 5C much quicker to clamp and release a work-piece. Also, something I find very useful, is that un-machined, "emergency", collets are available. And everything said above.

Regards Barry

I too have both types of collet. A point worth noting is that 5C collets will grip short lengths right at the nose of the collet, where ER collets need a fair bit of shank to grip. Makes each type have advantages!

Rgds,

John

Hi Guys,

Thank you all for your interesting comments - they are really appreciated.

Perhaps I should state that I have the full range of 5C collets and accessories which I use in conjunction with my Warco WM280V-F lathe. As John said the C5 collet will grip short pieces of work which I have done intuitively.

About a year ago I dumped the R8 Clarkson Tool holder fitted to my Naerok (old but still useable) mill as I found them to be too fiddly and awkward to use.

I began to use a Chester Tools ("ER" style) set of 8 collets in the mill with the supplied R8 tool holder.

The Chester collets are to their own design I believe. The set arrives with 3,4,6,8,10,12,14 & 16mm collets. Spare collets from Chester are very expensive and it really makes it untenable to make up a full set.

I started to realise that the ER32 collet range would (seemingly) fulfil my needs complimenting the C5 collets, and the existence of a C5/ER32 adaptor clinches the deal as this can be used in the lathe, spin indexer, Stevenson's blocks etc. In effect a no-brainer!!

Those were my thoughts, and although it sounded reasonable, I still couldn't fathom out the reason for having both sets until I read Clive's answer when he said that ER collets were designed for tool-holding and 5C for work-holding.

So, this has resolved my reservations and hopefully Santa will be reading this!

Cheers, Barry

Now I know what you want them for I would agree that ER 32 are the way to go.

I too had one of the slightly obscure MT3 collet holders that came with my Mill and did manage to get a few extra collets from ARC when they were clearance items. About this time last year I had just about decided to get an ER32 Flange mount chuck for my 280 when I was offered a new 5C chuck for £20 so changed my plans. I use the 5C on the lathe with a set of 1/32" increment collets as most of my work is imperial, they also fit a JS indexer that I got at a good price.

I also got a MT3 ER32 collet holder with imperial and metric collets (common sizes) and that is what I now use for all my tool holding and if working on metric use the adaptors for the 5c chuck and indexer. Go for one of the bearing nuts from ARC or RDG as they allow them to be tightened with less effort, I've not had a tool move in mine.

J

Fully agree with all above but what constitutes work holding to tool holding both spin at high rpm?

Used to 'have' to use Chester and proper German made ER32 I couldn't tell the difference by eye and wouldn't recommend either. Your old Clarkson easier to change cutters and collets plus the actual cutter wont drop as would those ER things. Serious and or critical work used to take in my MT3 collets and never had any move except in the Chester supplied ones, fully recommend ARC.

I wouldn't read too much in to ER being able to clamp up to 1mm less than size, it seriously has less and less clamping force than size which is not all that great when 'excessively' tightened up.

Clincher for me in op position since already has a full set of 5C is adapt mill fitting to take 5C collets or opt for finger type MT collets that are not widely marketed and don't induce unnecessary load on bearings.

Jon

Tool holding involves gripping a hardened shaft with the full or nearly full length of the parallel holding portion of the collet. Hardened steel on hardened steel is not a very grippy combination so needs considerable force to grip properly but is a very solid fill on the collet. ER collets exploit the high forces and full fill to improve accuracy and stability but they are potentially unstable at lower forces and partial fills. Where potential becomes actual is probably incapable of any meaningful general definition and in practice heavily dependant on how the user approaches the job.

Work holding involves gripping "any" material tightly enough to prevent it moving under cutting forces but, preferably, without marring the surface. This latter is most especially important as collets are often used to accurately grip machined to size parts of components so that work can be done on other parts without objectionable loss of concentricity. Its convenient if work holding systems can hold relatively short components in an adequately satisfactory manner so long as suitable adjustments are made to machining techniques to compensate for lesser grip. Short in this context is probably down to about half the length of the gripping portion of the collet. Its unreasonable to expect anything shorter to be held adequately.

5C collets are able to hold shorter components because the collet is generally fully stabilised by the spindle bore and does not generally rely on the component being held for anything other than the necessary reaction against closing force required if grip is to be produced. However if the component is too short the collet jaws will tilt and both concentricity and grip will be lost. In extreme cases the collet will be damaged.

Clearly in a practical world there is considerable overlap in the regions where a work holding collet like the 5C and a tool holding collet like the ER series will do equally well at holding cylindrical objects but ultimately design tells and one or the other will be superior for specific purposes outside or close to the boundaries of the overlap region. Given that such boundaries are invariably more than a little fuzzy experimental exploration is something to be avoided unless its the only way. Especially as, in my case at least, collet work tends to have a good deal of time invested before it gets anywhere near the collet.

Clive

Edited By Clive Foster on 30/11/2014 22:39:44

Further to Clive's excellent notes ...

This article on 'Workholding Collets' is worth a look.

MichaelG.

Just seen your latest post Barry.

From comments here, some might worry about using ER collets for work holding. Used sensibly, in my experience they will perform perfectly well in this role. It should be remembered that the Hobbyist usually has quite a range of work holding options available to them and that each tends to have its own advantages (and disadvantages). Personally, I wouldn't try to hold really short work pieces in my 3 jaw either for instance. So ER collets are not a cure-all but certainly can be very useful for some applications.

You also mentioned 'Chester' collets. Several of the Asian importers sold these sets and they were generally referred to as "Chinese" collets I believe. They were slightly longer than their ER equivalents. I had a boxed MT2 collet chuck using these collets at one time. They worked just fine but I decided the advantages of going to ER (wider choice of chucks and accessories - as well as collet sizes) outweighed keeping them - so sold the set on.

BTW - I was a bit surprised to see that you found your Clarkson collet holder awkward to use. In addition to the ER32 & 5C collets I mentioned earlier, I also have an MT2 Clarkson. I always use this in preference to other holders whenever I have a threaded cutter to fit my (limited) Clarkson collet set that will also suit the work. It's not that I don't trust the ERs to hold but simply that I view the Clarkson as being the superior system (albeit less flexible - in terms of my available cutter type/sizes). I know that the cutter will not 'walk' in the collet if properly set.

Not that I've had any problems with ER's holding work or collets but then (as stated earlier) I'm not pushing them really hard. I have had a collet walk when I was working with a Bridgeport many years ago using a 'simple' collet holder and a 19mm cutter. Over a 12" cut, the cutter was pulled in by about 0.25". Of course, I was being aggressive and having taken quite a few roughing cuts was probably trying to hurry things along. The work was ruined.

Moral - use the best holding system you have, take it easy and (above all) pay attention!

Regards,

IanT

Thank you for your comments Ian.

I think the attitude in the home workshop should be along the lines of 'this is not piece work' so taking both more time and lighter cuts will tend to produce the desired result. I have taken on board your Bridgeport experience for when I get to use the ER collets!!

I'm going to purchase the ball bearing type ER32 nuts from Arc Euro which seem to have better closing qualities than the regular nut.

Regards,

Barry

Hi Barry,

This is just for clarification.

About 14 years ago, most of the importers were offering the 'Chinese non-standard ER style' collets. They are not unique to any specific importers design. We just refer to them as Chinese 'non-standard' ER, which are a little longer than ER. the REAL reason why they were sold instead of ER, was that 'in theory' they were cheaper than ER . However as years went by, it transpired that the non-standard ER were more expensive than ER collets.

Some Chinese exporters, importers and users still hold the belief that the non-standard ER are cheaper.

Ketan at ARC

I second the use of the ball bearing ER32 nut, they make life so much easier. For some jobs I've even closed it by hand when making light cuts on small stuff!

Holy collet confusion batman! How is one meant to know if we are buying the standard ER or ER style collets?

Tony

Just found that the Rego-Fix website has dimensions of the ER collets, as they invented them I believe that would be a good place to start.

Tony

And the dimensions of the Chinese ones to compare with

Jason,

Very interesting, and a little worrying !

Compare with the Arc drawing of [presumably] standard ER dimensions

I wonder if the difference in both angle and length means you can [unfortunately] put ER collets in a Chinese pattern holder ... If so, it might explain why some people have problems with grip. [*]

[forgive me if this is drivel ... I'm full of dental anaesthetic]

MichaelG.

.

[*] Edit: Looking at the numbers, I don't think it should be possible to mix them up.

Edited By Michael Gilligan on 01/12/2014 19:01:49

MichaelG,

Dimensions of standard ER collects as shown in your ARC link are correct. I don't think it is so easy to put the ER into the non-standard Chinese, but I could be wrong.

We moved over to ER - when I got to understand the difference, around 2004. Demand for non-standard Chinese has been reducing heavily over the past ten years. Enquires for them are rare nowadays. Still semi-popular in East European countries who have connections with Russia, as non-standard Chinese and Russian engineering share common interests.

Ketan at ARC