Which collets to buy, never had my own before

Hi All,

I am hoping to get my new lathe at the end of this month and wil be needing to do some work on smallish (up to 10 mm diameter and below) turning for seating bearings. I really want to challenge myself and the machine, after settingup, feeling that collets may be the best means of work holdoing.

In the past I have been loaned various collets of several types from generous friends. I rarely took any interest in the sort of collet, only in its performance in my early ML7, which I no longer have.

My new m/c has a 4MT spindle of 26 mm bore.

I have seen some discussion on hrer but I'm not clear on the conclusions.

Which collets should i buy, ER type perhaps ER25, seem commonly available but what about others,

Opinions most welcome.

Jerry

I think it's probably fair to say the balance of users on this forum prefer the ER series, because they hold odd sizes well and securely, aside from a few 5C diehards. Specialist toolholding collets like Clarkson are just that, and not very flexible for workholding instead.

ER25 will hold up to 16mm, but if you have a lathe that big, consider ER32 or even ER40. Costs more per colllet, but you don't have to buy the bigger ones unless/until you want to.

Neil

Good luck choosing, I'm still undecided which ones to go for !

I use 5C purely because I obtained 2 chucks and a large selection of collets at a reasonable price.

Having imperial collets in 1/32 steps and metric in mostly 1mm increments covers most eventualities.

A few spare collets and some 'emergency' collets, one can be made to size for one off jobs.

The other advantage with 5C is that they are available in square, hex and round.

CB

The decision depends partly on how deep your pockets are and partly on the maximum and minimum diameters you want to grip.

For all components (chucks and collets) ER40 costs significantly more than ER32 which costs significantly more than ER25.

ER25 has collet ranges of 1 - 16 mm dia

ER32 has collet ranges of 2 - 20 mm dia

ER40 has collet ranges of 2 -26 mm dia

The collets can generally accept diameters up to approx 10% or so smaller than their nominal diameter but not significantly larger. (Rule of thumb is they will take 1mm smaller but that's doubtful for the very small sizes).

The chucks of the larger sizes take up more room (of course) and have larger through bores.

Edited By OMG on 05/09/2013 16:59:30

I need er40 really but can't make my mind up which brand !

I have ER32s they are great for holding cutters and tools on the mill, I use 5C's on the bigger lathes and DA200s on my Cowells. The choice all depends on the accuracy you are looking for. Spindle fitting or nose fitting will restrict the length of work they can hold.

Most people are not looking for the sort of accuracy that a precision collet set can provide. The cheap lower tolerance ERs meet most modelmaker's needs.

Jo

Thanks to everybody,

I'm still not sure of the best way to go. For me precision is what I am lokking for. ER types seem most popular but I take Bogstandards comments to heart. I have looked at his link and the holder he makeswith more than a little interest.

Looks like I shall have to do some more studying. As yet I don't understand the reasons for Jo's use of 5Cs but I hope to find out.

Jerry

One of teh advantages of 5C collets is that they allow one handed tightening due to the fact they fit into a chuck that is worked by a tee handled key in much the same way as the usual 3&4 jaw versions. The good ones are also made to a higher accuracy than cheap ER collets. Biggest disadvantage is that you can't really use them on a mill so need a second set of collets for that.

Good ERs and a good chuck for them will give good results and with a suitable holder can be used in the mill as well. You will need a C spanner and a means to stop teh spindle rotating when you do them up so not quite as easy as 5C. I would go for ER40 so you can make maximum use of teh 26mm spindle bore and reduce having to change to a 3-jaw so often

You could get a short MT4 to MT3 reducer and then use MT3 collets but they need a drawbar to pull them tight into the spindle so you can't hold long work.

Having said all that I rarely use collets just a good 3-jaw or 4-jaw.

J

I've made two ER25 collet holders, the latest from an oversize MT3 blank arbor from Arc Euro Trade. The runout using one of tyehir standard collets is within the spec for the collet itself.

Neil

A number of reasons I prefer to use my 5C's in a lathe:

1, Yes they only operate over a very narrow window but then most of our drawings are to the nearest 32nd of an inch, 5C's as standard can be brought in imperial sizes (and metric) so they will fit the work perfectly . ER's operate over a wide range of sizes typically for the cheap ones 1mm that means that most of the time they hold on 8 points not all the way around. Only on one size will the curve on the inside of the collet match the work piece. So most of the time as Jason says a good three jaw will be as good.

2, If you look at Neils photo you will see that most of the ER collets have a chamfer on the inside of the nose, that limits the minimum depth you can hold on. I often hold small work on less than 1mm in a 5C without any worry.

3, My 5C's go up to 28mm, my ER32s only 20mm. But 5C's don’t limit you there as you can also get expanding collets and oversized soft ones that let you make special sized collets go up to 3". Also brass and nylon ones that are designed to let you do clever things with.

4, I have not got a face mounting ER collet chuck so if I used them on the lathe I would be limited in the available depth.

5, I have got a Stephenson’s spin indexer which takes the ER collets but most of my work is in imperial sizes so I might as well continue to use the 5C’s in the head to hold them. One day I might find a need to use the ERs in the spin indexer if so they are available.

6, The 5C collet chuck is very nice to use, faffing around with a spanner to tighten the ERs on a lathe without a headstock lock is a pain: I tried it once and didn’t bother again.

But If I am doing smaller stuff I will opt to use the Cowells which means that I will be using the DA200’s which start at 1.2 mm and go up to 10mm in 0.4mm steps, so in many ways the 5C’s are more accurate than even these ultra precision collets, but the Cowells is so nice to use when working to extremely small tolerances. If I want to go smaller then the watch maker’s turns come out and that is a totally different ball game.

Jo

Edited By jason udall on 05/09/2013 22:40:41

Forgot to mention: I use Clarkson Autolocks on my mill for cutter holding, the ERs are used for parallel shank tooling except FC3s which have their own chuck. What is interesting is that only 3 of my set of 21 ER collets have ever been used (the rest still have their plastic wrappers on).

I also find that as the ER collet chuck is shorter than a standard drill chuck sometimes I use them to hold a drill when head height is short. If I am even tighter on head room then I use Morse taper collet. And if you get a 2MT ER collet chuck you could use it in the tailstock of the lathe, or in the rotary table.

Jo

I would start with ER25 as the smaller ones take less force to do up and you want to start at 10mm. Then you can add ER40 later for bigger sizes if you like them.

If you start with a Plate mounted collet chuck you can get it true.

Get a nut with rotating inner as it takes less force to get things tight.

You can them add a morse taper holder to use in tailstock to hold drills etc, much less prone to slipping than a Jacobs type chuck.

WNT do nice collets at a reasonable price

Steve Larner

Hi to all contributors, with thanks,

It looks as though the advice tends to a choice of 2,

ER perhaps 25 or 32 relatively cheap but not the most accurate, or

5G much greater accuracy and cost.

As I have a particular job in view for when my soon to be machine is set-up and levelled, (as discussed in another thread perhaps I really mean aligned?) and this has bearing blocks (brass) to be turned to an accuracy of +- 0.0025" with a mating shaft 105mm long x 20 mm +- 10 microns diameter I might invest in a 5C collet and see how I get on.

Note to self: I must convert 0.0025" to metric!

But in my industry we have to be familar with both systems as often a lab. will work in microns, mm litres tonnes etc when production works with older machinery much dating from the 20s and driven by line shafting still in imperial gallons , and in cu.ins as well as in real money like feet, inches and thou. Our Amerian cousins in the same industry use the US gallon and mils. No wonder we are still confused.

I gather this 20 mm diameter is at the top of the ER capacity range. I don't seem to be able to find an authoritative source of collet dimensions. Not even Tubal Cain's last edition of Model Engineer's Handbook (2003) gives much detail.

Hey Ho!

Jerry

Arc's site give sthe basics, the two ranges against the sizes are because the smaller sizes go in 0.5mm steps and the larger in 1mm steps.

For accuracy on a shaft then turn between centres or just buy PGMS (prceision ground mild steel)

For accuracy on bearings turn OD and ID at one setting and then part off, no need for collets

Also look at the accuracy of the collets you are buying as Jo pointed out earlier, for example J&L/MSC sell three qualities, on teh ER32 these are standard 0.01mm, Super 0.005mm and Din 6499 0.02mm. As you can see with the Din ones you will be hard pushed to get your 10microns. Thats why some ER32 collets sell for £4.99 and others £30plus

Edited By JasonB on 06/09/2013 20:48:52

Don't forget you also need to consider if your lathe can meet the standard of accuracy that you are asking of your collets. I know that one of my lathes doesn't .

Jo

The tolerances quoted are on dimensions, nothing is said about concentricity? Collets may help on concentricity but they'll have little bearing (!) on the accuracy of a dimension. May be the problem needs to be better defined before settling on a solution?

Andrew

The figures I quoted were for "collet runout accuracy" not very well placed out on the page as the title is not next to the table. Note the little clock image on the drawing.

J

Edited By JasonB on 06/09/2013 21:42:57