MT4 collets

[John HaineParticipant @johnhaine32865]

[John HaineParticipant @johnhaine32865]

Does anyone know of a source for MT4 collets please?  I’ve got a large-bore S7 with MT4 taper, I can use MT2 collets with the MT2 adapter but these only go up to half-inch.  It would be nice to hold a few larger diameters, but I don’t fancy forking out for a 5C chuck, so the ability to buy the off MT4 collet as required would be nice.

 

John.

[Keith LongParticipant @keithlong89920]

There are a number of places selling MT3 collets, go up to 3/4 inch 16mm. You could use those with at MT3-4 sleeve.

Keith

[HasBeanParticipant @hasbean]

ER40 collet chuck any good? Generally stop at 26mm but collets are available up to 30mm.

 

Paul

[John HaineParticipant @johnhaine32865]

Thanks for the responses.  I’d thought of MT3 but that only gives a limited increase on max diameter from my MT2 set, and the max size I have seen is 18 mm, not 3/4.  ER is another possibility but would need an adapter – nice to have collets that close in the native taper because much shorter overhang.  I think I might have a go at making one, see how it turns out.

 

John.

[Richard ShuteParticipant @richardshute14275]

You can get MT4 collets via J&L in the US, but with the current Sterling Rouble they will be very expensive, especially as J&L charge a surcharge on them as they are not standard UK stock.

You can also get them via ebay.de note DOT DE that’s the German version of the site

Search for “spannzangen mk4”, mK4 = Morse Konus 

eg item 350308785084 is a set of 3~25mm, a snip at Eur239 😐

Good hunting

Richard

PS I gave up and made mine, but then, although my pockets are deep, my arms are very short

[John HaineParticipant @johnhaine32865]

Thanks Richard – looks like making them is the best option then.  Any tips on how you went about it please – what material especially?

 

John.

[Richard ShuteParticipant @richardshute14275]

Hello John
I did all the turning work on a slightly less than optimally big S&B Sabel (Southbend clone-ish). It’s a super machine, but the top slide travel is a bit marginal for this job. However, the outer diameter is ‘accurate’ only over about 2/3 of the length, the upper portion is reduced by 010~020 so that the collet can close with out risk of nipping the solid shank in the quill bore so you can turn the OD in two goes. Obviously make sure you turn the accurate OD and the bore without moving the work from the chuck or you will loose concentricity and it won’t be a very useful collet…
I threaded the shank before taper turning as it’s quite hard work being 5/8 Whit and holding the work might risk damage to accurate surfaces doing it afterwards. I used a MT4 dead centre between centres in the lathe and a DTI on the tool post to set the compound slide to the angle.
After all the turning I held the collet in the dividing head and split it with a slitting saw. If I did it again I would make a tapered bore socket to hold

the collet on the reduced diameter while doing this op. as the Heath-Robinson scheme I used had a bit too much pucker factor for comfort.

Material wise I used some ‘tough stuff’ I had in the box. It came from some scrap MT5 dead centres I reclaimed and tempered in the woodburner overnight, but you don’t need to go overboard. It depends a bit on your use, but you can make pretty servicable collets from mild steel, but something hardenable would be nice. A chunk of En8 would be a fairly cheap and easy option and as a simple carbon steel is pretty straight forward to heat treat at home if you want. Some En19 if you are feeling a bit extravagant. En24 would certainly do well, but is a bit OTT for home use. The ‘usual suspects’ really.

Richard

[mgjParticipant @mgj]

John – might you not be in danger of getting in a bit technical.

 

Certainly if you are planning to use these collets on an industrial/production basis, then you would be well advised to make them out of a good hardenable steel. Take your pick – I don’t use the old EN numbers. And if you want to do it right, you should machine, harden and then finish grind.

 

But if genuinely you are a model engineer, and you want, as you indicated, collets for occasional use in larger sizes, – particularly as plain drawbar collets which don’t have to accommodate much compression (unlike ER collets) – then I am surprised that you would consider anything other than dear old free cutting mild – 220M07.

 

I have various fittings and holders, some for a GHT VDH, which I use pretty regularly which are still absolutely sound after nearly 30 years. All from free cutting mild – they remain true, to size, release well and don’t mark the job.

 

I accept – wouldn’t stand up to production wear and tear, but most of us model engineers don’t even have machinery that would stand such loadings?

 

Another case of the best being the enemy of the good?

 

[John HaineParticipant @johnhaine32865]

Thanks for the replies….definitely free-cutting for me, and I won’t bother with hardening.  As my lathe now has CNC this will be an interesting test of its capabilities.  I already have a set of Myford MT2 collets with the closing ring that threads on the spindle nose (with an adapter of course), and I plan to use a similar approach but with a larger ring so that long bars can be accomodated rather than use a drawbar.  I won’t bother to make them self-extracting (like the MT2 ones are) but use my trusty bit of broom handle to knock them loose!  The most useful thing is knowing someone has successfully made them.

 

John.

[mgjParticipant @mgj]

Are you sure its wise not to make them self extracting?

 

If you are going to hold long bar, then to remove said collet you will have to tap the bar, unless resorting to long and complex sleeves. You run the risk of damaging the soft  collet bore. You only need an unseen nick in the bar and that could possibly be the end of that collet.

 

I’m all for keeping it simple, and the broom handle or an ali or brass drift will work fine under  normal circumstances. But not always.

 

One of those no free lunch scenarios.

 

Edited By mgj on 07/04/2010 22:58:26

[John HaineParticipant @johnhaine32865]

Well, maybe use a bit of tube rather than a broom handle…..the h/s bore is an inch, so max material diameter can’t be more than say 7/8 allowing some meat at the back of the collet, so a bit of pipe 7/8 bore and 1 in od ought to go over the material and sneak up the back of the collet to knock it out.  Just looking at the Myford pattern collets, there seems to be some tricky dimensioning of the groove in the end that the closing ring engages in to make sure that the collet is held properly to extract it but can close up enough to be able to be fitted into the ring.  My worry is that if they are not hardened then closing them to fit the ring could deform them.

 

[mgjParticipant @mgj]

Soft ali tube might be best?

[chris stephensParticipant @chrisstephens63393]

Or perhaps just case-harden the end of the collet, if you feel there is a risk of damage from  ejection. Personally I would counter bore the none business end slightly and likewise reduce the OD , so that there is room for damage, no matter how unlikely.

chriStephens 

[Ian WelfordParticipant @ianwelford58739]

I made a ram rod out of steel tube with a nylon plug in the ned about 1/2 thick and domed slightly. Won’t dmage the collet and the nylons expendable.

 

Just a thought

 

Ian

[Ian WelfordParticipant @ianwelford58739]

I made a ram rod out of steel tube with a nylon plug in the ned about 1/2 thick and domed slightly. Won’t damage the collet and the nylons expendable.

 

Just a thought

 

Ian

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