MC2 collet on myford

[davp1971Participant @davp1971]

Hello, does anyone here have experience with mc2 collets in the spindle of a myford super7? I am still in the discovery phase of the myford? I want to try everything.
I do know that the collet is tensioned with a drawn bar. How hard do you have to tighten it? I have also read that sometimes the collet is firmly fixed in the spindle. It is then recommended to ‘knock’ on the drawn bar with a hammer. Doesn’t this damage the bearings of the spindle? is it a good tip to add oil to the collet before mounting? Any tips are welcome. THX

[John HaineParticipant @johnhaine32865]

I assume you mean MT2 collets.  Yes you can use them and you need a drawbar.  The latter is conveniently made fro a length of studding of the right size to fit the collet thread, usually 3/8 whit for imperial or M10 for metric collets.  Make sure socket and collet tapers are clean, a drop of oil a good idea.  Don’t over tighten.  Release with a light tap on the end of the drawbar.  Don’t leave the collet tightened in place after use to minimise sticking. Not so good for long stock as you can’t pass it past the end of the drawbar. If you can get hold of a Myford closer nut it will fit the front of the collet but nut give the release feature.  Proper Myford pattern collets are like hen’s teeth but very good.

[Clive Brown 1Participant @clivebrown1]

More correctly MT2, (morse taper). Tighten firmly but not excessively is my best description, enough to prevent the workpiece slipping. You may have a problem stopping the collet rotating in the mandrel as you attempt to tighten the drawbar. Myford marketed a different system, without a drawbar, which avoids that.

Note that MT collets will only grip a workpiece that is close to the nominal size, within a very few thousanths of an inch. A trace of oil is good. The “knock” to release should only be, at most, a light tap, a piece of wood might be more benign than a hammer.

[John HaineParticipant @johnhaine32865]

If you put the work in the collet and press the collet in with finger pressure it should give enough friction to lock to allow tightening.  TBH I’ve never had a problem with the collet rotating.

I think the Myford bearing design should be pretty robust against axial shock loads, but as Clive says using a bit of wood or a rubber mallet might be kinder.

One think you should make (5 minute job) is a “top hat washer”, say 1/4″ long with a 1/8 spigot that is just a loose fit in the spindle bore and a 1/8 flange at least the spindle OD, drilled to clear the drawbar.  Use this to centre the drawbar at the outboard end of the spindle.

I did use MT2 finger collets in my S7 with a drawbar for a while but then lucked on a collet set which I’ve expanded over the years so I now have a full set of metric and imperial collets.

There was an article in MEW about making “Myford pattern” MT2 collets including making the closer nut that fits on the spindle nose.  It does look to me like one could modify off-the-shelf finger collets to fit a closer nut though it would involve probably grinding the required groove.  Myford collets are pulled in by the closer ring but it also extracts them as it’s unscrewed.  There’s a few sets advertised on eBay right now if you want to shock yourself at the prices.

[davp1971Participant @davp1971]

Thanks for the reactions. I was also thinking about making something on the end of the spindle to center the drawn bar. This is what you mean John, right? I know there is a lot to buy in UK, but i live in Belgium and the taxes that come with it are not small. so i try it this way.

The article from MEW was indeed interesting

I also had in mind making a closer nut.

THX

[Clive FosterParticipant @clivefoster55965]

Remember that, if everything is in good order, its not necessary to heave on the drawbar spanner for the collet to get a good grip.

MT collet jams are almost certainly due to over-tightening and / or distortion due to trying to grip outside the nominal range. MT collets are for tool holding an expect a shank very close to nominal size. Bridgeport R8 collets which cover a similar range and are also single ended have nominal tolerance range of round 10 thou, 0.25 mm (ish). Don’t have to be very far out before the collet starts to distort in a attempt to grip things.

For what it’s worth Bridgeport reckon something between 25 and 35 ft lb is fine for R8 collets.

I imagine that an MT collet will be happy at similar torque levels.

Clive

[Chris CrewParticipant @chriscrew66644]

FYI, the MC range of collets is a Burnerd product that would fit the LC15 chuck. The MC2 collet is nearly as big as your fist so absolutely not suitable for a Myford!

[DiogenesParticipant @diogenes]

Maybe a Morse collet will be happier at lower torques than BP quote, as the angle is much shallower than an R8 collet?

I use a ?100mm ring spanner with the my thumb right next to the ‘head’ and three fingers against it’s neck and it’s more than adequate.

When ‘knocking out’, I was taught that a short, sharp rap with a light brass or copper hammer is more likely to shock the collet out whilst inertia damps the spindle than heavy blows from something softer.

[Clive FosterParticipant @clivefoster55965]

Diogenes

Morse taper is significantly longer than the R8 closing taper which, with coupled with the shallower angle, means more friction losses. Different drawbar thread pitch too.

For practical purposes things probably more or less even out to end up with a similar working torque range.

25 to 30 ft lb really isn’t very much. It’s instructive to calibrate your spanner pull estimate against a torque wrench. Like most folk I’m way over down the bottom end if I don’t concentrate. Ex car or motorcycle valve spring gives a nice load.

True work holding collets like the 5C series run even less torque. The hand wheel closer for the collet set on my S&B 1024 is only about 7″ diameter. Plain semi-polished aluminium rim is all there is to grip it by. No way is that getting seriously heaved up.

Bottom line is if a single ended collet doesn’t hold at moderate torque it’s time to investigate.

Clive

P.S.   ER are double ended and different. Regofix, the inventors publish (relatively) hefty torque specifications for a good reason.

[davp1971Participant @davp1971]

[davp1971Participant @davp1971]

I lean these things.
<p style=”text-align: center;”>Best regards</p>

[davp1971Participant @davp1971]

<p style=”text-align: left;”>I mean these things.</p>
Best regards

 

[davp1971]

On davp1971 Said:

Thanks for the photo, I was getting confused!   MC2 as a typo for MT2 made sense until Chris mentioned Burnerd and then I found this beast, also MC2:

 

An ER25 collet chuck working hard enough to heat damage the machine is new to me!  But production being brutal, there must be times when it makes sense to cool the chuck.    Obviously every Myford owner should have one!

🙂

Dave

 

 

 

[noel shelleyParticipant @noelshelley55608]

I have seen home made Myford type collet nuts, but my recollection is that the original Myford unit had a hardened face as a separate part held in by a crimped/rolled edge. Myford/ RDG do a ER32 collet holder to screw onto the spindle nose and the 2 piece one can be set/trued to best run out.

There is always the Myford Lever operated collet chuck for rapid production ! Followed by the cut off slide and then go the whole hog and fit the 6 station bed mounted capstan.  Good Luck, Noel.

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