How to use direct collets?

[cidrontmg]

I bought some M2 taper direct collets to use in my mill. They would save quite a lot of vertical space, which is always at a premium, small mill (Quantum BF 16 Vario). Problem: how do I hold the collet (and cutter) when tightening (or loosening) the drawbar? I also have some tools with an M2 shank (a dovetail cutter, for instance), with exactly the same problem.


The collet extends below the quill almost exactly 5 mm when itīs tightened (as in the picture). There are 3 equispaced cuts in the collet, 1.5 mm wide when not tightened. Iīve put a bit of 1 mm spring steel into the cut, and worn a thick glove, to be able to use the collet at all. But thatīs too complicated. There must be some sort of a tool for this. How does it look like?

BTW. The obvious solution would be to drill a hole to the collet, and use a bar. Except the collets are hardened. And in the 12 mm collet, which would need the most torque to tighten, the wall thickness is just 3 mm at its thickest point. And, a hole would introduce imbalance, and thatīs exactly what I donīt want...   
 

[Bluechip]

Not quite sure what the other end of the draw-bar is, but

The arrangement seems to be like the one I had on my first Myford ML7T
I tried a long hex headed bolt to draw the collets in, but it didn't work. Bit like yours maybe?

Then, on advice from someone who knew of these things, replaced the bolt with a draw-bar screwed 3/8" BSW at the collet end, and a sleeve nut threaded 3/8" BSCy, (26 tpi), at the other. This nipped up straight away. No need to hold the cutter at all. Never came out un-heralded as it were.

Not Myford collets, Crawford IIRC. Was 2MT.

Not sure why it should be any better, but it was.

Dave BC

Edit

Just remembered ... did give the collet/cutter a light tap with a small lead hammer to seat it, after that they stay in while the nut is nipped up.?

Tried that ?  You should be able to hold the doins with the spindle flats then.

Not sure whether this has any relevance whatsoever ..    Zebedee calls   

[John Hill]

Can you 'wring' the collet into place? That might hold it while you screw the draw bar in and tighten it,  to get it out loosen the draw bar then give the head of the draw bar a bit of a tap to loosen the collet.

Thats how I manage tapers on my lathe anyway.

[Bogstandard]

You should be able to spin the drawbar down into the collet by hand until it starts to grip in the spindle. If it doesn't check below.

Take out your drawbar and make sure that the collets screw onto it very easily. If they don't, run a tap down the collet threads until they do. Be careful though, MT fittings can have a choice of two different threads, some are metric, some imperial. Either M10 or 3/8" Whitworth, both very close to each other in pitch/tpi.

A friend had the same sort of problem, and he found he could easily recut the threads in the collets from Imperial to metric with no ill effect on the grip. That choice would have to be yours.

It might be that the threads on the end of your drawbar are just too long for the collets, in that case just make up a collar that sits under the drawbar head, say 3/4" long.

Been in this situation with my old mill, but in MT3, I ended up with two drawbars (two different threads) AND a collar just for the sake of it.


Bogs

[cidrontmg]

Thatīs what I have now.


The collet set has 3/8 x 24tpi (UNF) threads, I made a drawbar for them, the rightmost one.
The extra collet has a 3/8 x 16 tpi (BSW) thread, the drawbar for it is in the middle. That drawbar also works with lots of other tools acquired from England, of course.
The original drawbar is M10 x 1 (fine) thread, on the left. It fits most of my stuff, drill chuck, ER25 collet chuck, etc.
Donīt you just love standardization...
All the threads are very easy fits in their resp. tools, "tuned" with split dies.
Thereīs also two brass washers in the middle drawbar, to adjust the length of any of them. I can fix any tool I have, easily, securely, but without unnecessary force - except the collets. I just canīt hold the collet tight with only 5 mm protruding from the quill, without doing awkward contortions.
Iīve been thinking about something like the tools used to extract oil filters, but in miniature. The collets are 18 mm dia. at the end, and of course, slightly tapered (M2). So thereīs not much for the band to grip on. But such a tool would have also the advantage that it would close the collet around the cutter, and prevent it from falling down when it is being tightened. Something like this.


That is for diameters from 50 mm up, so maybe not usable with 18 mm... But the idea seems worth experimenting. Is there something like that, but small, ready-made, or should I cobble one up myself?

[kwackers]

If you look at the middle drawbar (as an example) it has a square head.

So what you'd do is this, drop the drawbar in, and spin it into the collet by hand (thereby engaging as much thread as possible). Next you'd use two spanners, one on the nut to tighten up whilst holding the top of the drawbar still with a spanner on the square head.

When making drawbars, I put two nuts on, one to tighten it and another right at the top which I pin to the bar to hold it stationary ( a small 'tommy' bar can be usefully fitted here instead of the nut).

If the cutter is loose in the collet, then I nip up the collet a little first until it's tight enough for me to slide the cutter in and it not to slide back out.

(Hope this is what you mean)

[Bogstandard]

I have never come across collets other than the two threads I mentioned.

Have you tried pushing the collets up into the quill with no cutter or draw bar? The rounded end should only just protrude out of the quill, with none of the taper showing. If that isn't happening, there is either something wrong with the MT standard used on the collets or something inside your quill stopping it going all the way in. There should be nothing protruding to get a grip on with anything.

A MT taper is classed as self gripping, that means it should lock itself up and grip as soon as it has full contact over it's length (with a cutter in of course), that is how fitting one with a cutter works, as soon as it is pushed in until it can go no further, the cutter should be gripped and and not fall out, and the drawbar can then be tightened up.

BTW, MT collets are exact size fit only, that means they can only hold the one size as marked, they cannot reliably be used to grip any other size, so say if it is a 10mm, it cannot be used to hold a 3/8" shank imperial cutter, even though very close.


Bogs

[cidrontmg]

Hello Bogs, kwackers,
the collet set is this (the metric one)
http://www.rdgtools.co.uk/acatalog/2_MORSE_TAPER_COLLETS.html
and like they say, they have 3/8 UNF (=24 tpi) threads. Thatīs no problem, the 3rd drawbar has that thread. I hope I donīt have to make any more drawbars, though.
When the collets are pushed in, they protrude some 4.2 mm from the quill, with no cutter. The slits in the collet close at that point. With a cutter tightened, itīs 5 mm. The same with the "extra" collet (3/8 x 16tpi) from another seller. 5 mm is not much to get a grip on, for sure. Thatīs why I wasnīt over-enthusiastic about the oil filter tool-lookalike.
All the drawbars have a square 8 mm head. With the mill came a tool that looks like a lathe chuck tool, except thereīs an 8 mm square hole where the lathe tool has a square head.
Iīve been thinking about this, and one possibility would be a piece of tube, with a hole the size of the cutter (might need several tubes for various cutter sizes), and a length somewhat more than the cutter. Put the cutter in the tube, with "something" to keep it in there (styrofoam or such) against the business end. Then push the cutter in the still loose collet (with the styrofoam), keep the end of the tube against the collet, and whack the other end of the tube, so the collet closes, and grips in the taper. And then tighten the drawbar. It might even work, if you could follow the thinking...
All my cutters except one ballnose are metric. The one exception is a German Guhring with a 1/4" shank... I bought it from Germany, as a 6 mm. Oh well...
And as they say, one manīs light tap is someone elseīs almighty blow...
 

[Jonny]

Been using these type of collets for over 11 years plus R8 before hand.
Theres no way i would use anything else.

Simplified- Each collet has a tapped internal thread, you need a draw bar with that thread to match and screw up.
Small Clarke aKA RF25 mill i have three draw bars M10, 3/8 BSW and M12. Larger just buy everything M12.
To remove cutter or change collet, slacken approx 1/4 to 1/2 a rev and tap with hammer- out pops the cutter.
Simples

On the RF 25 i just used to leave the top cover off, its still in the loft 11 years on. I grab the pulley whilst tightening or undoing the draw bar- can change cutters over within 6 secs, so easy.
6 year ago upon buying a Super Lux the first thing i did was make a spindle lock, again simple push button in to vertical splines. 16mm spanner and hammer can change cutters within 8 seconds even quicker on the other mill.
No slipping either.