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

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

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

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

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

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

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

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

Tony

And the dimensions of the Chinese ones to compare with

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

Given the effectiveness and relatively low prices of ER collet sets I'm surprised that Model Engineer market machines are not made with native ER spindle tapers. Most especially the round column breed where the inability to raise and lower the head without loss of alignment constrains the user to fit both cutting depth and tool change space within the quill travel range. Seems to me that the complete coverage of a considerable size range would allow larger drills to be held in the collet rather than having to find space for a bulky chuck. Smaller drills would do fine in an appropriately sized chuck needing rather less depth. With an ER native spindle, but still through bored, spindle mounting the milling cutters in side-screw holders with relatively long parallel shanks would provide a bit more freedom in vertical position. Especially with smaller cutters. This approach would seem very advantageous in jobs where relatively large, and so long, drills need to be used on one part of a job and small, short, cutters on another.

Returning to the original topic I would disagree with Ian's statement that the Model Engineer has a wide range of work holding options. In practice the interests of domestic harmony and, probably, adequate nutrition means that every hobby £ spent needs to do the work of 5, preferably 10, so equipment constraints are a fact of life. What the Model Engineer does have is freedom to adjust the manner of working and approach to the job. This freedom can range from creative circumvention of the limitations of multi-purpose equipment when compared to more specialist counterparts though activities that the proper engineering books would consider cheating and on to outright fraud. Whatever works. It helps to have a really good understanding of exactly how the equipment being considered for creative exploitation works and what it was designed to do. It being somewhat depressing when creativity runs out on the second to last cut.

In retrospect the most economic approach for me on replacing my BCA with an R8 spindle square column machine would have been to get a set of side-screw cutter holders rather than the ER32 collet set as I had already decided to purchase a spin-dexer and 5C mount chuck. If my lathe had been fitted with a screw nose spindle a matching thread on a 5C blank allowing chucks to be shared would probably have done just as well. Given the relatively limited range of milling cutter shank sizes used by the average ME i'm inclined to think the flexibility of collet systems is perhaps over-rated and that more consideration should be given to proper exploitation of parallel shank side-screw cutter holders. Main disadvantage is the need to grind flats on the cutters for the screw to grip.

Clive

I wasn't thinking so much in terms of multitudinous bits of (expensive) equipment for the hobbyist Clive – so much as the many 'methods' of work holding available to us – many of which can take a good deal of time to set up perhaps but not necessarily cost money.

For business 'Time is Money' of course but the hobbyist is generally making one off parts and can usually find some creative way to hold the work if necessary – even if it involves making something else to do it. But from your comments I don't think we actually disagree too much on this. Of course, I will admit to having quite a lot of "engineering stuff" – far more than I really need (or use that often to be honest) but it has been gathered over quite a long period of time, so hasn't really cost a fortune (at least not one that my wife has noticed fortunately).

What else to say? My shed (and all my treasures in it – which my wife sometimes unkindly refers to as "all that scrap"  )  gives me a great deal of enjoyment. You could also point out to your wife (as I frequently do to mine) how much cheaper a 'Shed' is when compared to Golf Club Membership. It doesn't entirely work of course but it does seem to help reduce the general level of 'comment' about my engineering purchases.

Regards,

IanT

Edited By IanT on 02/12/2014 00:47:00

Edited By IanT on 02/12/2014 00:47:26