ER collet size help

Hi All,

I have been given a large collection of ER collets (sandvik 393 series) but they are a non standard size according to the Spec. the OD is 25.45mm (Nom ER25) but the length is 40.0 mm (Nom ER32). Heaven knows where id get a collet holder.

Has anyone any idea if these are of any use or should i just bin them.

Regards

Paul

Probably too good to bin.

First find someone with a 25 collet holder and check that they might fit (say this because there was 6 or 7mm clearance in the back of the ER32 holder I use.

Otherwise, just make a collet holder to suit your requirement, seen some drawings in one of the threads here for basic dimensions, obviously you will have to make radial dim to suit 25s and axial to suit 32s checking to see if there is any change to angular tapers. If the nose angle is as per standard you can save work and just purchase a 25 collet closer.

Edited By Martin of Wick on 11/12/2020 15:13:34

Hi Paul,

If you want to use your "special" ER 25 collets in an ordinary ER25 collet chuck with a MT or R8 shank you may be lucky and find a chuck that will accept your special collets. You will probably find that some machining is necessary, a carbide tipped tool should be up to the job. I have a slightly larger ER 32 chuck and it would be possible to make room for longer collets. If you want to use the collets for workholding in your lathe you could just make your own collet chuck. That is what I did for my small lathe, and the chuck is used quite often.

Thor

Edited By Thor on 11/12/2020 15:37:40

Have you measured the angles? 30 degree front and 8 degree back. If not the same why not make your own holder to suit? Sounds as if an ER25 nut could be used as a closure if the front angle is 30 degree. Seems a pity to waste such a gift horse and if they are SKF manufactured they would/should be pretty good.

I happen to have some new er25 collets. They are 34mm long and at that length, the diameter is 19mm. This is the free diameter, and if you set calipers to 19mm and the diameter of yours is about that at 34mm from the front end, they might fit an er25 holder.

I tried googling Sandvik 393 collets and the result was very different from an er shape.

Edited By old mart on 11/12/2020 15:36:22

I never even considered making a collet holder myself! i have a set of ER32 collets and holder for the mill but nothing for the lathe.

I will check the angles tomorrow and then try to think of a a way to make the useful on the lathe.

Thanks all for the suggestions.

Regards

Paul

If you have some er32 collets, you could compare them against the mystery ones, all er collets look similar and their angles match.

Making a holder is fairly trivial, I made one successfully quite a few years back when I had very little idea what I was doing! (Not that I do now mind you...)

• Make a backplate to closely fit your spindle nose with a suitable spigot on the front on which to form the holder. Make sure it can go back in the same position on the nose so you can get repeatability in use.
• Set the topslide to the taper by chucking a bit of ground bar that's a close sliding fit in one of the collets, sliding on the collet, then using a DTI in the toolpost set the topslide to get a zero-zero reading on the tapered side of the rear taper (being careful to avoid one of the slit grooves).
• Mount the assembly on the spindle and turn the spigot to size, make the closer thread to suit a standard collet closer nut (of course this assumes that the front taper and groove suits)
• Bore out the spigot for the minimum diameter and bore the taper to fit the back collet taper. You're done!

Could you have a look inside the collet, specifically at the back.

These ones:

https://www.sandvik.coromant.com/en-gb/products/pages/productdetails.aspx?c=393.14-20%20d060x049

are for tapping and the extra length may possibly be for the square at the end.

Thank you John.

I'll check the angles tomorrow

The bore through the collet is round. Here are some photos,

the part number yields v little info

Looks nice quality

They are definitely not er collets.

I have some similar, came with 'multi machine (lathe/mill) I bought from a friend who was getting divorced (paid him same as he paid for machine, felt sorry for him)

It's closer to a Morse taper but doesn't match MT3

No idea what standard they are but interested in finding out

Edited By Peter Jones 20 on 11/12/2020 18:19:34

The characters after the dash on the first line of the part number are the LETTERS 'O' (for orange) and 'Z' (for zebra).

If you put that part of the part number into Google, you get to:

https://www.sandvik.coromant.com/en-gb/products/pages/productdetails.aspx?c=393.01-oz%201825

which gives a reference of DIN6388.

They are likely OZ collets.

http://www.collet.com.tw/en/product-c109321/OZ-System.html

That's impressive searching, my 'Google fu' isn't strong like yours

I think they could be EOC16 collets, the size looks right. **LINK**

Din 6388 is the classification, as DC31k says.

Edited By old mart on 11/12/2020 19:32:56

Big difference in the back taper angle for the EOC collet - 2.52 degree versus 8 degree for an ER - they must be high precision collets and are worthy of being used - even if you have to make a collet holder. As I said in my earlier post if the front angle is 30 degree then an ER25 nut may be a nailed on bet for a closure nut.

I believe they are for woodworking routers, the industrial type.

I think we have a winner!

The Spec says its a EOC16A collet, and the front angle is 30°

Since they are split from both ends, they will be flexible, like ER collets.

Being Sandvik, the quality will be good

If an ER clamp nut fits the front end, I would be tempted to make a collet holder for them, so that they can be used.

Not being skilled enough to make them, I buy my Clamp Nuts.

The pitch for ER Clamp Nut threads is 1.5 mm. I have made holders for ER collets for various jobs, (Tap holders, Collet Blocks, drll / end mill holders for grinding ). If I can do it, you surely can!

Howard