|Luke Mitchell||05/06/2020 17:06:36|
39 forum posts
I am re-tooling a Myford ML4 which I have been restoring (thanks to many on this forum for guidance there!). I've now got the spindle running somewhat truer and the lathe seems to be in very good shape, which I'm happy about.
Unfortunately, the 3-jaw self-centering chuck that came with the lathe is rather worn and it is almost impossible (for me, at least) to re-chuck work with any repeatable accuracy. One of the jaws is marked with a cross but my experiments using this alone, all jaws sequentially, etc. for tightening doesn't seem to make much of a difference. As such, I have been working using the 4-jaw independent chuck recently and getting much better results.
Whilst a new chuck is definitely on my to-buy list I am quite interested in purchasing some collets. These will give me the best accuracy for the machine and I will be able to hold smaller and more delicate workpieces safely and without marking them.
I am currently weighing up the options and have come to the following three:
The first option is the easiest but perhaps the most limiting. I hope to purchase a mill over the next few years and, in the event that the mill does not come with collets, it would be easier to re-use the ERC collets.
Also, I have read that it is quite easy to jam the collets into the spindle by over-tightening the draw bar. How much of a problem is this in reality?
Concerning the ERC collets, am I likely to lose a lot of precision in using the taper-mounted chuck? Is there any real disadvantage to using this over the spindle-mounted version, which will require me to make up a backplate?
Finally, is there any disadvantage to opting for ER40 over 32? Obviously I can only go as small as 3mm using an ER40 but the collets go considerably larger than the ER32 ones.
Any thoughts or experience welcome.
|John Haine||05/06/2020 17:28:35|
|4170 forum posts|
Before long you'll want to chuck a bit of bar longer than an MT2 finger drawbar collet will take - remember that the standard drawbar is 3/8 too so that's the max size of the hole. Myford pattern collets are better but very hard to find and expensive, though you can make them (see recent thread on here somewhere). They use a closing nut that pushes them into the taper socket, they are bored to nominal size right through. Any finger collet of this sort only works on a very small range of stock diameters near the nominal size.
The same limitation on diameter/lengthapplies to ER (what are ERC?) collets on a taper shank. Save those for milling. They also stick out a lot for turning in my experience.
Easy to make a backplate for a front-mounted ER collet chuck - actually you can make the whole chuck in situ yourself for precision, only have to buy a closing nut.
If you go for ER40 it'll take bigger stock, but except for short bits you'll be limited by your spindle bore. Which is more useful for you - length or diameter?
I have a set of Myford pattern collets built up over the years; a full set of imperial and metric MT2 finger collets I bought rather mistakenly but sometimes are useful; and an ER40 chuck I bought from the old Myford (I have a large bore S7 so the larger diameter is useful, and for smaller stock I have the MT2 collets. I probably use the ER40 more than the MT2 Myford collets, and more than the 3 jaw chuck.
Edited By John Haine on 05/06/2020 17:32:10
|Martin Connelly||05/06/2020 17:33:02|
1888 forum posts
Stevenson's block in the 4 jaw?
The 2MT in the spindle takes up least room but is limiting if you want to pass long items through the spindle. The same issue arises with the ER32/40 collets and 2MT chuck.
|Thor 🇳🇴||05/06/2020 17:40:58|
1411 forum posts
I would recommend an ER chuck that mounts on a backplate - something like this. I made an ER 32 chuck that mounts on the spindle of my small lathe, ER 32 because I already had some ER 32 collets. The chuck can take long bars up to 20mm dia. and has good repeatability. With an ER chuck that mounts on a backplate you can easily move the chuck to another lather if you decide to upgrade the ML4.
|1895 forum posts|
I have ER32 chucks mounted on backplates for my lathes, they work very well - although I do have a couple of MT2 collets brought for specific purposes and one of which now acts to hold a depth stop when I need one.
Standardise on a single size of ER - ER40 is larger but I have other ER32 devices such as collet blocks, spin indexer and MT mounted chuck (for the mills) - so one set of ER32 collets fits all.
|Clive Brown 1||05/06/2020 18:01:45|
|706 forum posts|
Not answering the actual question, but I'd put purchase of a decent 4" SC 3 jaw chuck as a far higher priority than collets. Much more versatile for general work IMHO and avoids the hassle of changing collets at frequent intervals. Accuracy for 2nd. ops. should be good enough for most work and there's always the 4-jaw as a fall-back.
If I did eventually go for collets, I'd not be keen on 2MT with drawbar, as being too restrictive in workpiece length.
|540 forum posts|
I am no expert, and I am sure someone more experienced wil have better arguments, but here is my pennies worth.
Re 3 jaw chucks, don't get your hopes up about new chuck accuracy. From what I gather from this forum and books is that 3 jaws in general are quick and dirty. If you want to re-chuck, use a 4 jaw. The exception to this is if you have an adjustable 3 jaw, where you can re-center the work by moving the whole chuck.
Re collets, it all depends on what you make. If you are likely to often work with bar between 33mm and 41mm then go for the ER40. I don't have lathe collets, but am looking at getting them. For me I would be interested in smaller sizes than large. I more often have trouble holding small items than large. I already have ER25, so will use them, but if buying new I would go ER32.
After looking at the same options as you, I have decided on a backplate mounted chuck. I will probably make it myself and buy a nut. That way I have the same access to the spindle bore as a normal chuck.
|Howard Lewis||05/06/2020 18:59:22|
|5298 forum posts|
A 3 jaw self centering chuck is unlikely to provide concentricity much better than 0.005"
It will probably hold a wider range of round or hexagonal material, reasonably concentric, than an expensive range ER collets.
A 4 jaw independent chuck will allow you to centre work (or to deliberately run it eccentrically if you so wish ) as accurately as you are your DTi can measure.
This will hold square, octagonal or irregular material concentrically, if that is your wish. Again the maximum size that can be held will be greater than ER40 collets.
No matter what chuck you fit, the 2MT bore will limit the maximum size of material that will pass through the Mandrel to about 1/2".
Buying both a 3 and a 4 jaw chuck is likely to be less costly than a full range of ER 40 collets.and a Backplate.
A conventional chuck will allow you to hold larger work than you can in an ER 40 collet chuck.
ER collets will allow you to hold Metric, or |Imperial material, as long as the difference in diameter does not exceed 1 mm (0.5 mm for the smallest collets )
The choice is yours, dependent on the budget. All three types have their uses, and so are present in my shop, The ER collets are used in the Mandrel, and the Tailstock of the lathe, as well as on the Mill, for work or toll holding, when the need arises.
|old mart||05/06/2020 19:14:30|
|3345 forum posts|
Spend some of your money on a lever indicator and stand and you will get to appreciate how good the four jaw independent is. The er32 on a plate does give you the deeper through hole than any other collet system, but you will have to buy the full set of collets to go with it which will cost more. Assuming your old three jaw is on a backplate, a new one of the same size would be cheaper than the collets and easy to set up.
21435 forum posts
You could do a lot better than 5thou but not if you buy cheap chucks, I get less than half a thou runout on my 3-jaw, less if I use the soft jaws.
I would get a decent 3-jaw SC before looking at collets.
|Former Member||05/06/2020 19:42:36|
[This posting has been removed]
|Luke Mitchell||05/06/2020 19:43:21|
39 forum posts
Many thanks for the responses.
I'm happy with my 4-jaw and the indicators I have - I've got a few that I have picked up 2nd hand, including a Mitutoyo lever-type, and they all seem to agree with one another so I deem them reasonably trustworthy!. I am able to get work held in the 4-jaw to the same accuracy as my spindle, about 0.015mm (~0.0006" ), within 5 minutes or so.
The ease of a decent 3-jaw is rather appealing and perhaps I should heed some of the advice concerning that. Jason, do you mind if I ask you the maker of your chuck and what you'd consider to be a decent, not "cheap" model? I'm aware that you can get new Chinese chucks from eBay/Banggood and such for around £100 but I'd rather buy something used, reliable, and preferably European.
Speaking of Chinese tooling, there are fairly complete ER32 collet sets available for sub-£100. Are those suggesting the collet route will be expensive of the opinion that these are not trustworthy?
There is a lot to consider as a result of this. It sounds like a spindle-mounted ER32 collet chuck would be the best approach. I may hold off a while longer and look into replacing my 3-jaw, however.
Edited By Luke Mitchell on 05/06/2020 19:48:36
|Clive Brown 1||05/06/2020 19:52:23|
|706 forum posts|
Just a brief point. I'd be very cautious about buying any used 3-jaw of any make, European or other. It could well be for sale due to losing its accuracy from abuse.
Edited By Clive Brown 1 on 05/06/2020 19:57:49
21435 forum posts
I run a 125mm Bison 3274, Another member tipped me off a couple of years ago for some NOS selling for £100 which was a bit of a bargain, Rotagrip will want £500 for one at the moment, I did get the soft jaws from them. It is mounted on the original Warco backplate that the supplied 3-jaw came on with no modification and the dti shows just over one division of a 0.01mm dti.
Also have a 160mm Bison slim bodied 4-jaw that was second hand.
When I do use collets on the lathe I use 5C mostly unless I don't have the size then use a 5C to ER32 adaptor.
Like most things you get what you pay for, very cheap can be pot luck, mid range should be OK and top shelf stuff should be good.
|1895 forum posts|
Just reading your initial post again Luke and want to just address this issue of three-jaw chucks. I have a few, some old and some virtually new - however, I don't expect any of them to re-chuck 'true' on second operations - e.g. once I've removed the work for some reason and then have to rechuck it.
I wouldn't expect any of mine to do so and it is best to make this assumption from the get-go and simply plan your work accordingly. It is often possible to think of ways to re-order work - or in some cases just to keep work in the chuck and remove the whole thing (work and chuck) from the lathe to drill or mill a feature.
Sometimes, you just have to accept that perhaps the work needs to be re-clocked in the four jaw - or just turned between centres (which seems to be a bit out of fashion these days) if you are going to need to take it in and out often as you progress. As mentioned, I do have collet chucks - but I do not expect to go from 3-Jaw to Collet and have absolutely zero runout afterwards, in theory there should be none but in my experience there is often a little.
Finally, a 3-Jaw - even a worn one (provided it can securely grip the work) will turn work true and to size - it just needs sufficient 'spare' material to turn away to get rid of any 'eccentricity'.
Good luck with your new lathe!
|Nick Clarke 3||05/06/2020 20:58:50|
1253 forum posts
2MT collets - in a small milling machine these provide lots more headspace compared to an ER collet chuck, but this may not be such a good thing on your ML4 - a classic British gap bed lathe.
Small work may not project far enough from the nose of the spindle to be machined without the saddle hanging in mid air over the gap.
ER collets of either size will project more in their chuck and be more useful, and they also allow a (limited) range of sizes to be held in each collet unlike a MT2
Edited By Nick Clarke 3 on 05/06/2020 20:59:41
|Thor 🇳🇴||06/06/2020 10:38:09|
1411 forum posts
I bought a cheap Chinese ER32 collet chuck (with MT3 shank) and a few collets from Chester several years ago and the collet chuck had a run out less than 0.01mm on the inner cone. The collets had a bit more run out than the Vertex ones I bought later from another supplier. So you may be lucky and get a good one. I didn't buy a collet set, just the collets I have needed for my various projects. Both the chuck with MT 3 shank and the ER 32 chuck on the lathe are used often, I wouldn't be without them.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.