MT3 collets

[Peter G. ShawParticipant @peterg-shaw75338]

Both my lathe and my milling machine have a MT3 taper, and as a result, I have bought almost all the metric direct or finger collets I can find eg 3-6mm, 8mm, 10-14mm, and 16-18mm. However, what seems rather surprising is that I cannot find 15mm. Same with 7mm and 9mm except that so far I haven't encountered a need for those.

I have looked at imperial collets to see if there was one of a similar size and found that the nearest are 9/16in (14.29mm) and 5/8in (15.87mm) neither of which are going to be suitable.

Does anyone know where 15mm collets may be obtained? Or am I going to have to attempt to make a sleeve to fit inside the 18mm collet bearing in mind that this will require a wall thickness of 1.5mm?

I suppose another idea might be to attempt to make my own collet, but this really would test my skills.

Peter G. Shaw

[Peter G. ShawParticipant @peterg-shaw75338]

[RichardNParticipant @richardn]

If it's just a one off job I would think about a quick split sleeve to hold in the 18mm, I'm trying to think what the wall thickness is like on 3/4" copper plumbers pipe…

Or there are some 15mm MT3 collets around, but can't see them in any of the normal online shops I use.

http://www.ebay.co.uk/ulk/itm/131173200327

[Speedy Builder5Participant @speedybuilder5]

In the old days, we used a thing with three lumpy bits called jaws – I think the whole thing was called a chuck.

[JonParticipant @jon]

Never seen certain sizes ie 15mm and have to ask why?
No cutters are that size and you wouldn't want to use them MT3 collets in a lathe unless don't want them out again. Unless head stocks a small bore with MT3 up the spout you would need a draw bar making as well.

Fine choice for mill work next best thing to R8 use em daily and would not dream of going ER.

MT3 in tail stock require a tang to stop rotation and ejection whether wedge or by hand wheel.

[Peter G. ShawParticipant @peterg-shaw75338]

RichardN,

Never thought about copper pipe so been to measure some old 3/4in stuff. 21mm od so too big. And no it's not the new 22mm stuff. But thanks anyway.

Looked at the reference – rather expensive, roughly twice those from the usual suppliers.

SpeedyBuilder5,

On this particular project I've used: 100mm 3-jaw self-centring, 80mm 4 jaw independant, 160mm 4 jaw independant and 12mm MT3 collet. So I'm certainly not averse to using chucks, the major problem being the requirement to use a time consuming DTI to set up the work. A 15mm collet would have made life somewhat easier.

Jon,

No cutters are that size and you wouldn't want to use them MT3 collets in a lathe unless don't want them out again. Unless head stocks a small bore with MT3 up the spout you would need a draw bar making as well.

I find having the collets handy and quite useful at times as long as the work is the same size. Extracting is reasonably easy. Drawbar exists so no problem there.

Before I got the milling machine, I eventually found that the best, most reliable way of milling was indeed to hold the cutter in a collet in the lathe headstock.

Not being made of money, I deliberately bought my milling machine with MT3 so that I could use these collets in both machines.

Tailstock is MT2. Furthermore, my lathe has no provision for a tang to stop rotation. I have had to remove tangs on two adaptors yet ejection still occurs via the handwheel. I have never experienced slippage on the MT2 tapers yet I have had slippage between the drill chuck and drill bits.

Overall, I work in metric, and find the collets very useful. Any designs I do are always in metric. Often, I end up turning down to a collet size, and then I change to the collet for 2nd, 3rd etc operations where possible. A good example would be when using 6mm. I have a quantity of s/h free-cutting 1/4in stuff which tends to get initially turned down to 6mm in a chuck, then transferred to the 6mm collet and further turned down or drilled as necessary.

Probably the biggest, maybe the only, snag is that I can't hold long lengths of material, but for up to (guess) 75mm inside the collet, they are fine.

I think that when the present projects are finished, I might have a go at making one, just to see if I can. A quick glance at the 12mm collet shows that although it looks as if it is MT3 for the full length of the collet, in fact, only the gripping end, about 50mm or so, is going to engage with the inside of the mandrel. The rear portion, although tapered, is slightly less in diameter. Which means that I can turn it in two sections and thus it is within the travel of my topslide.

Thanks for the comments,

Peter G. Shaw

[Howard LewisParticipant @howardlewis46836]

If you can/are prepared to, stand the cost, you could go for an ER system. ER 25 will take up to 16mm, ER32 to 20mm.

Costs can be reduced, a little, by making your own Collet Holder, (Quite simple, cut a 32 x 1.5mm, or 40 x 1.5mm thread, an 8 degree set over for the Topslide, and buy the clamp nut and collets) Since it was turned on the mandrel, rather than in a 3 jaw chuck, it should run pretty true next time, AND you can make it through bored to allow longer material to be turned. The handy thing about the ER system is that the larger, (>3mm), collets have a range of 1mm, so are literally flexible on size, and can accommodate Imperial material.

From memory, I think that a 3MT Mandrel is 29mm bore, and ER40 will hold up to 26mm, if you want to turn larger material.

Just a thought!

Howard

[Roger HeadParticipant @rogerhead16992]

Posted by Jon on 30/06/2016 14:59:18:

… No cutters are that size …

You can buy anything in this world… The seller in the following link has endmills from (I think) 1.5mm to 20mm, in all integer values, and many with x.5 values e.g. 5.5, 8.5, etc. I've no idea how good they are, some of the brands illustrate parts showing HSSAL marking, but who knows?? I'm contemplating getting a couple, and a T-slot and dovetail cutter, now that CTC seems to have disappeared forever.

http://www.aliexpress.com/store/product/Brand-new-5PCS-4F-M15-0-full-grinding-mill-Milling-cutter-High-speed-steel-end-mill/1724275_32358769434.html

Roger

[JasonBModerator @jasonb]

I think I would just pop a bit of bar into the 18mm collet, bore to 15mm, mark it's position before taking it out and sawing down the side. I've used this method a couple of times when I did not have the size collet I wanted and it held the work/tool no problem.

[AjohnwParticipant @ajohnw51620]

I think I would just make a few collet blanks copying the designs that do come in a lot of sizes. The length of the taper looks to be shorter and a parallel section on the end. Setting up for the first one may take some time but making a few more no time at all really. The parallel section should make it easier to slit them after they have been bored to size but emergency collets usually come with a small bore and slit.

I'd make them taper towards the tailstock so that it can be checked with a morse sleeve using blue. My dore westbury came with one made like this and I can't help wondering why the person who built the machine didn't make more.

John

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