Thread: collets : to chuck or not to chuck

The ER32 collets will hold stock of varying sizes (generally 1mm range per collet size) whereas the MT collet will only hold the size specified. So if you are holding a mix of imperial and metric items the ER32 will cope (a 13-12mm ER32 will hold 1/2" whereas a 13mm MT collet will not).

The ER series collets clamp more securely than the MT collets due to the architecture of the slots in the collet.

Using the ER collets in collet chuck makes it quicker and easier to change collet sizes as the drawbar stays in situ.

The ER32 chuck uses more of your mill's headroom though.

On balance the ER collets and chuck are more useful and flexible than the direct MT collets in my opinion. They can be used in the lathe and the mill.

You would have to be out of your mind to buy the Morse collets.

Seriously, ER is so much better with easy insertion, quick release, no stuck collets, cheap, accurate, that other system is stone age.

Rob

Thanks for the replies.

Job done will order the collets plus chuck.

Bill

Originally Posted by steamingbill

OK ............ following advice given in another thread (flycutter caused chuck to jam tight on headstock) am investigating collets. (birthday soon)

This collett ER32 COLLET - IMPERIAL #F6300

has to be mounted in a collet chuck and then a drawbar is attached to the collet chuck to secure it - a metric or imperial set of collets is available from CTC for approx $75ish and a chuck for $20ish

This collett C136 | 3MT Collet | machineryhouse.com.au sits directly in the taper on the headstock and needs a drawbar to secure it

Could somebody please kindly give me some pointers as to why and in what circumstances one of these would be preferred over the other ?

Thanks

Bill

Advantages of Morse collets in a Lathe:

- fits directly into spindle.
- no need for a collet chuck that can add runout.
- minimum overhang
- cheap


Diadvantages of Morse collets in a Lathe:

- MT collets are NOT SELF RELEASING. Need to tap collet/workpiece out.
- Need a drawbar. A hollow drawbar will limit through spindle diameter. A plain drawbar will make stock feeding through the spindle impossible.
- MT collets only have a very narrow clamping range. They essentially only fit the nominal diameter, plus zero mm and minus maybe one or two tenths of a mm before loosing precision.


ER collets were originally designed for toolholding. But are successfully used in home shops also for workholding. Key advantages are low cost and a large clamping range of typically 1mm, except the very smallest diameters below 2mm. This means that only half as many collets are needed to gaplessly cover the entire size range, compared to the typcal lathe collets like C5 or Schaublin etc. Making ER collets even cheaper. And in a home shop even more savings are possible because the same set of ER collets can be used for the lathe and the milling machine.

For lathe use, the choice of collet chuck makes a difference in cost and in usefulness.
- The cheapest is to use an ER milling collet that mounts into the lathe spindle taper and is retained by a drawbar --- BUT this means forfeiting through spindle feed capability. Its an acceptable choice for milling in the lathe to hold an endmill. But not a very good idea for workholding.
- Next up is a solid one piece collet chuck (plus the nut) that mounts to the spindle nose and allows through spindle feeding. But such collet chuck is of dubious accuracy if it was not made on the lathe it is to be used on (except if the spindle nose is fitted with a standardized and accurately registering mount such as camlock). It is easy to home made such a collet chuck, the hardest part is the nut (because of the internal retaining excenter) but ready made nuts can be bough for very cheap on eBay.
- ready made lathe collet chucks for ER collets do not use a normal castellated nut, but a purpose made taper shaped nut which is tightened by tommy bars. This is because with a collet chuck, you often work very close to the chuck and at very high rpm, for example when polishing something. A castellated nut is dangerous if a polishing rag get caught, or if your knuckles touch the nut. Being able to safely work very close to the chuck is one of the key advantages of a collet chuck, beside the ability to re-chuck without undue loss of alignment, and of course low runout overall.

EDIT: you originally ask about an imperial ER collet. Note that ER collets where invented by RegoFix in Switzerland. Thus they are a metric collet system. Single split collets have 0.5mm clamping range, double split collets have 1mm clamping range. For example, a 10-9mm ER collet has a nominal size of 10.00mm. It has it greatest accuracy and clamping force at 10mm. You damage it if you try to clamp any larger. But you can use it down to 9mm. So to cover gaplessly a range of say 1 to 20mm, you need 20 collets. That does not work with imperial ER size collets, because the size steps are not linear. Also watch out, some are selling "fake" imperial collets. 1/4" is 6.35mm. Some makers mark a 7-6mm collet as 1/4", but you got to close that collet by 2/3 before it can hold a 1/4" endmill, and you got to undo that collet nut quite a bit before it releases that endmill again, and accuracy and especially clamping force are compromized. Whereas serious makers make a real 1/4" collet that has 6.35mm nominal size. But use of such "real" imperial collets will need more pieces to cover gaplessly, are hard to get, and do always cost more. Hope you get what I mean: if you think and work in Inches, then ER collets may not be the ideal answer for you.