An ER collet chuck will hold most cutters, the threaded end cutters are the Clarkson Autolock design, the Posilock and Dormer Fastloc were other versions. With some care in positioning the cutter the ER will hold any typical cutter, the thread and whistle notch are not useful parts for the collet to grip so position in the collet needs care.

Mike

Lets' step back, or rather, vertically upwards, first….. Finding INT30 tooling at reasonable prices!

"Ours" – ARC Euro, RDG etc. – stock mainly R8 and Morse taper fittings, but ARC has some INT30 and INT40, ER-collet chucks explained below.

Cutwel might sell INT-taper holders, though not listed on their web-site – most of their stock has other types of spindle tapers, mainly for modern NC machines with tool auto-changers.

Please if someone else can suggest a suitable dealer, do so!

I would be wary of e-Bay because you want decent-quality tooling and you've no idea what you are actually buying on such sites. If you have to search second-hand, as well as advertising here you could do worse than – as I have done – try Home and Workshop Machinery, and G&M Tools. Both firms advertise in ME, and though second-hand most of their stock is ex-industrial, college, etc.

…..

Right, now step back down the spindle and shank, to the cutter.

There are three basic ways to hold a milling-cutter: 1) collet-chuck for screwed-shank cutter, 2) plain-shank direct collet, 3) plain-shank side-holding.

1) Of the screwed-shank collet-chucks the best-known is probably the Clarkson 'Autolock' but I think other, similar makes are/were available. The difficulty is finding collets for these and you would probably have to think second-hand.

The Autolock style chuck has a cylindrical body whose blind bore has a large central point that locates the centre-drilling in the top of the cutter. The tool is screwed into a collet of the right shank size, then this assembly is screwed into the chuck body by a special "nut" with tangs that drive the flats on the collet. As it is tightened the collet's coned inwards end is pushed into a taper that closes it tightly onto the cutter shank.

The beauty of this system is its repeatability of setting and the positive location and gripping.

Its disadvantage is the depth of the chuck below the spindle, limiting space for taller work-pieces and set-ups.

'

2) The Plain-shank direct collet come in two forms, and they can hold screwed-shank cutters with some provisos because the thread is slightly smaller over its crests than the shank diameter.

– a) A long, split unit pulled into the spindle by the draw-bar, tightening onto the cutter shank by its taper engaging the spindle taper. Type vary. The Morse collet is tapered for its full length. R8 collets have a short taper at the nose end only. I don't know if there is an INT-n version.

Their advantage is in holding the cutter is held as closely as possible to the spindle nose, maximising rigidity and work-height range.

Disadvantage – I have had cutters slip in such a collet, but that may be a result of wear. Slip, part from being bad for the collet, can make the tool retreat. Worse though, and I have had this happen, it can make the cutter think it is a self-acting drill and plough down into the work.

'

– b). The ER-collet. This is a short, multlple-split cone held in a matching chuck by a closing-nut. The chuck shank is pulled into the spindle by the draw-bar, but the tool is gripped separately, by the collet. The collets are through-bored so can also be used with a suitable nose-piece, as precision work-holders on the lathe (NB – good-quality material with decent surface finish, only).

Their size ranges are designated by numbers – I've not managed to establish the number's meanings, but as a guide, an ER32 chuck's collets range from 3mm to 20mm diameter capacity.

The ER collet-chucks are compact but do reduce the day-light a bit. A big advantage is that a lot of tooling is easily-available to use these collets as work-holders.

Note that the ER collet does not just post itself into the chuck but is held via an eccentric washer, so there is a simple but definite procedure to using them. They are tightened and loosed by a special spanner that should be supplied , or certainly bought, with the chuck. And use that, not makeshifts giving the results so sadly shown on so many much-used machines and accessories!

ARC does list ER32 and ER40 collet-chucks with INT-n shanks.

'

3) Plain-shank side-holding. ARC calls it just an " End-mill Holder ", but not in INT-n sizes. It is a simple body with a grub-screw to engage the flat on the cutter, and shank to fit the spindle. It used to be possible to buy a miniature version with a screwed shank to hold in an 'Autolock'-pattern chuck, for the very small, short-shank cutters often described as " throw-away " in industry, due to the difficulty and cost of re-sharpening. I am not sure of the wisdom of holding such cutters in an ER collet, which is really intended to hold over its full length.

'

So… let's sum up.

All your cutters can be held by any of the above but if you cannot find an 'Autolock' pattern chuck and its collets the ER system is probably next best and very versatile.

Though I suggest not using an ER collet for a cutter shank shorter than itself, no doubt someone will come here and say, " I do! No problem ! " . He may be right, but I prefer to play safe with expensive tooling.

You could turn a simple grub-screwed holder from ground-finished steel for the smallest cutters, to hold in a larger ER collet. Ream the bore.

The use and action of the Autolock chuck differs from what has been posted.

The collet is placed into the screwed sleeve, with driving flats engaged. The collet can float axially a little. The assembly is screwed into the chuck body, until the sleeve's flange meets the chuck body's face. It does not have to be tight. The cutter is screwed into the sleeve, until it bottoms out. Its centre is then engaged with the centre point in the chuck body. The sleeve is then nipped tight with the spanner, for security. Note, this is not to tighten the collet (read on).

When cutting torque is applied to the cutter, it tries to screw the collet out of the sleeve, whilst pushing against the centre point. The male taper on the outer end of the collet then engages progressively more firmly with the female taper in the sleeve, thus tightening the collet.

The beauty of the design is that the chuck is self-tightening, and the cutter cannot work out of the chuck.

I thought like the Osborne version you have to go up a chuck size after 5/8" or 16mm?

Hi Me.

I am surprised that there isn't any Morse collets hidden in the tool collection.

In any event a quick sort and survey will help guide your choice of investment. If the majority of tools have standardised diameters then the choice gets easier. Equally if you know you are only going to do small stuff.

Before you make your mind up, have a close look at your cutters, they often look sharp from a distance. Also the size range, as I said, the er25 goes to 16mm, and the er 32 goes to 21mm.

I have a cantilever toolbox with about 500 threaded shank milling cutters from 1/16" to 7/8" and every one would require sharpening before it was any use on a mill.

They don't but may need a different length drawbar. In another thread I mentioned that bt30 finger collets are available.