Operating a Myford 254 lever collet chuck

I am puzzled by the operation of this chuck and I can find nothing on line. It appears to have been made by Pfander. This is what I have been doing:

- load collet (163E)

- fit closer loosely

- place workpiece in collet

- tighten closer so that the lever has about about 1/4" of slack

- push lever to right - this locks the collet

To remove the turned article:

- push lever to left

- undo closer with spanner

My expectation was that a collet would be mounted and closed to a sliding fit over the workpiece. The lever would then lock it in place and subsequent operation of the lever in the opposite direct would release the article.

Am I doing something wrong, or am I expecting the chuck to do something for which it was not designed?

Edited By Chris Pearson 1 on 20/09/2019 10:29:20

Edited By Chris Pearson 1 on 20/09/2019 10:29:51

I last used a Burnerd lever collet in a Myford Super Seven 45 years ago, which should work in a similar way. The object of the mechanism is the speed of use, so when the closer is set for a little slack, then operating the lever should clamp the work, or release using only the lever. This should work if all the workpieces are the same od.

Edited By old mart on 20/09/2019 14:35:48

I am having another go at this one please.

I have had the chuck in pieces and there is no possibility of assembling it wrongly. The sleeve which holds the collet is a very firm push fit in the body of the chuck.

Pulling the lever to the right squeezes 6 ball bearings inwards, which pushes the sleeve and collet away from the headstock and on to the closer. Pulling it to the left releases the ball bearings, but there is nothing to push the sleeve back towards the headstock so it stays where it is.

As mentioned previously, one option is to unscrew the closer. Another one is to give the workpiece a sharp tap with a leather hammer, and the third is to use the tailstock to push the sleeve back.

It still seems odd and I wonder whether anybody knows any more please.

Hello.

I am used to the Myford lever operated collet chuck for the ML7 & S7 lathes.  Old Mart’s description of how the chuck is used / operated matches my experience for successful loading and unloading of turned parts.

My experience of the 254 and its accessories is very limited, so I am not aware if Myford (Beeston) made their own collet chuck, or this was provided by another company. The name Pfander is not familiar to me. May I suggest a couple of pictures of the unit. This may initiate a response from someone with more knowledge.

best regards. Alan

Edited By Alan Donovan on 31/10/2022 19:55:18

Just in case it will help, here is an exploded diagram of the ML7 lever-operated collet chuck:

This diagram isn't very good at illustrating how the operating lever is connected to the lathe head-stock.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 31/10/2022 20:18:09

Hi.

After re-reading your enquiry, and studying the ML7 / S7 collet attachement drawing, my first thought is that you should not be loosening the closer to release the part from the collet. Are you sure you are not tightening the closer too much in the first place?

I still think it makes sense to load a couple of pictures onto this enquiry so the forum members can see what the equipment looks like!

All the best Alan.

I purchased a Myford 254 in 1997 and remember seeing the chuck as an option (that I didn't get). Can you post a picture of it?

The 163E series collets are dead length collets so intended for operation where speed of operation is paramount. As old mart says it should be lever one way clamps the work in the collet, lever the other way releases the work from the collet. During operation the collet should not move axially. It should be possible to clamp work, machine, release work and insert next workpiece without stopping the spindle.

If the above isn't true then either something is missing, is misadjusted or is damaged.

Andrew

I think you're on the right lines, I have two collect chucks (different collet sizes) from the same manufacturer for my lathe, and have two thoughts:

1. my suspicion is that Chris is tightening the collet closer to be a very close sliding fit on the parts before actuating the lever, it's worth trying it a bit looser before actuating the lever.
2. My collets have little cylindrical rubber bits in the slits, which act as a sort of spring, if Chris's collets are absent these, or they've perished then it may explain the lack of spring back. (These could be non standard additions by my lathe's former owner, but they work)

I tend to put the collet in my chuck and screw up the collet closer until it just touches the face of the collet, and let the lever do all the closing, and it grips and releases fine.

As Andrew says the 163E collets are dead length and don't move. They rely on the natural spring of the collets to open them against any frictional forces in the mount when the closer is released.

Old collets get "tired" after long therm production use and may not have enough spring to self open as per specification when mounted.

Old collet mounts do wear which again may increase the opening force needed.

The system is much more heavily engineered than you might think at first sight. Everything has to be right. But when it is the results are very durable and very accurate. When it isn't. Nightmare.

Jacobs Rubberflex versions have resilient inserts between the collet fingers to permit greater collapse range and, incidentally a bit more opening effort. Sounds like Jelly has a sort of shop-bodged version. Hate to say it but if his collets need the extra spring of the rubber they are passed their sell by date and objectively scrap. Even if they still appear to work OK. Life is way too short to futz around with misbehaving collets. The Jacobs version has the rubber bits bonded in. Not a pretty sight when coolant and time eventually degrade things to failure.

Clive

I'm open to this possibility, but looking at manufacturer's pictures on the web, it would appear that (admittedly in sizes larger than 163E) the little rubber things do seem to be standard equipment.

Links to Kitagawa collets size: 173E & 185E by way of illustration.

Unsure if this is a foible of that particular manufacturer or of the larger DIN 6343 collet sizes.

​​

That said, even if they are objectively worn out, as long as they're holding concentricity properly, I'm not sure I could call them scrap given that new collets are between £84 and £100 each, with a complete set of 185E's coming in at £3411.48.

In a production environment sure (and I'd expect to build the cost of tooling into the job), but I don't get sufficient use out of collets to justify the outlay of replacing them whilst they still function even if imperfectly.

Edited By Jelly on 01/11/2022 10:30:02

Jelly

Interesting links to the Kitagawa collets.

I'd not seen that style before. Presumably having the resilient blocks lets the collet cover a little more range to easily accommodate material tolerances by driving it a touch past its natural spring open position.

I use 5C collets so its a bit less painful to bin a suspect one than when dealing with more professional, production level, systems. But not springing open properly is always the first sign that poor holding power and other issues will soon surface. Heaving on the handwheel to get a weak collet to hold gets old fast.

Anyway who in the home workshop is set up to properly evaluate whether collet performance is up to specification? Or even do jobs that really need collet capabilities. Mine come out when thats the most convenient way of doing a job, the extra accuracy being mostly a nice but unexploited thing. Not having to worry about a big chuck wizzing round holding a small job is, um, nice. I guess that generally applies to most home workshop folk.

Clive

Looking into it a bit more it seems like certain sizes within the specification for Dead-Length Collets do use the resilient blocks, but others don't; without buying the standard it's hard to know which is which.

​

I did notice that for my 185E chuck, a DIN compatible knock off of the rubberflex collets is available, offering a 3mm rather than 1mm clamping range on parts over 8mm in size... Although at £309 a collet, they would end up working out slightly more expensive for the same range.

Looking into it a bit more, it turns out the appeal of the rubberflex type DIN collets is apparently being able to grip black bar (as opposed to bright/centerless ground) for first-op machining on a production lathe with a bar feeder, thus saving money on raw materials.​

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I've done quite a bit of making smallish parts where concentricity and surface finish were key meaning I needed the ability to both move between setups without losing concentricity, and run at max speed (3500 rpm); injector cones, nozzles for atomising liquids, and a replacement spindle for a high speed engraver to name just a few.

The collet chuck was/is definitely a major quality of life improvement over doing work like that in a small 4-jaw chuck dialling it in with a "10ths indicator" (actually a 2μm indicator), especially with thin wall parts which are susceptible to being crushed... that sort of work could drive a man to madness done too often.

Edited By Jelly on 01/11/2022 15:44:10

Edited By Jelly on 01/11/2022 15:49:23

Thank you to everybody for your contributions - it has been a busy week and I did not expect so many after the lack of interest in my original posting.

I am not sure how much use photographs would be because they do not show the innards. However, if push comes to shove, I could disassemble again.

Instead of photos, here is a diagram, which is certainly not to scale, but I think does show the operation of the chuck.

The dark green is the spindle and the light green is the fixed portion of the chuck. The collet (grey) is held in position by the closer (yellow) and if it is not moved, then clearly the collet remains in the same position. Operation of the lever (black) moves the blue sleeve to the right and the taper pushes the balls (6) inwards. This in turn moves the red sleeve to the right. 1 inch of movement in the blue sleeve results in about 50 thou of movement in the red sleeve, and perhaps 10 thou radially of the collet. So as the red sleeve is moved rightwards, the collet grips the workpiece.

When the lever is moved to the left, the pressure on the balls is removed and the red sleeve is free to move to the left and release the workpiece. However, it seems fairly obvious, due to the taper, that springiness of the collet will not exert much force on the sleeve. Moreover, the red sleeve is a push fit in the light green one so there would have to be some positive force to move it to the left.

I cannot see how the chuck could have been assembled wrongly and I do not see how anything could have gone missing. Whilst there are witness marks to show the force of the balls to the right, there are none to the left.

Further contributions will be much appreciated.

Edited By Chris Pearson 1 on 05/11/2022 19:05:39

Edited By Chris Pearson 1 on 05/11/2022 19:07:09

Hi. Chris.

My request for a photo only needed to be an outside view, but your sectional view gives me the information that I need.

I still feel that you are over tightening the closer. If the closer (yellow) is over tightened it pushes the collet (grey) further in to the collet housing (red) thus closing down the collet. Try slakening off the closer (say one eight of a turn at a time) and then closing, and then opening, the collet with the handle mechanism.

I feel fairly confident you will come to a position where you can open and close the collet to load and unload your component without having to further adjust (unscrew) the closer to release the component. The handle mechanism will / should take up the additional slack in the collet and should still provide the necessary force to grip the component for machining.

I hope this helps. Please let us know if this solves the problem.

Best regards. Alan.

Alan, thank you. I have tried your suggestion, but unfortunately, it did not help.

If the closer (which isn't really the closer) is too loose, the red sleeve will reach the end of its travel to the right without closing the collet. If it is too tight, the red and blue sleeves are pushed back to the limit of their travel to the left and the lever becomes fixed.

The chuck works nicely for gripping the workpiece, but I can still not see any means of moving the red sleeve to the left.

This is v. frustrating, but I was only using it to obtain the best possible concentricity for a grinding wheel arbor, so I think that I can live with it.

I cannot even find operating instructions for any similar chuck. Surely there must be something out there!

Edited By Chris Pearson 1 on 06/11/2022 12:43:28

Given that these chucks work well and reliably for long periods in industrial use is it possible that the vibrations inherent to fast spinning stock and machinery provide the extra impetus needed to release the collet when opened. I imagine the balls jiggle around a bit too which may help.

Clive

Hi Chris.

Your collet chuck problem has been bugging me, so I am back with another possibility (maybe ? ?).

You say the internal sleeve, that holds the collet (red in your diagram) ..... is a very firm push fit in the body. Is it possible that the internal sleeve has a couple on 'bruises' on the OD that is causing this tightness. I feel this should be very close fitting but a 'free sliding fit' in the main body. If there is slight bruise present causing tightness, this may be a contributory factor.

Secondly, is there a circlip groove, in the bore at the nose end of the main body (green). If 'yes', then it may be a circlip has been lost / ommited. This circlip limits the forward movement of the internal sleeve and may make it possible to adjust the clamp / open setting of the collet correctly. If you look at the arrangement drawing of the Myford Collet assembly - as provided by Swarf, Mostly - there is a circlip fitted in this area to limit the movement of the internal sleeve.

That's it. Alan.

Alan, thank you for giving the matter further thought. I was beginning to think upon similar lines so when I have some spare time, I shall strip it down again and try measuring with a micrometer. I rather doubt, however, that an ordinary micrometer would be precise enough, but we shall see.

IIRC, there is no circlip groove.

I have the set including 16 collets from 1/16 to 9/16 in the original Myford case. I intend to sell the set but I need to know how to list it and roughly what to ask for it. The items ive seen on ebay are'nt complete and are on the British ebay. I dont know if this is appropriate for this site but im hoping some one will know and be able to let me know. Thank you