Myford ML7 Chucks – Which one?

[Mike PooleParticipant @mikepoole82104]

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

[Dr_GMJNParticipant @dr_gmjn]

Posted by mgnbuk on 05/02/2021 17:13:02:

I was surprised the jaws weren’t stamped 1, 2 & 3;

In your top photo of the new chuck showing the outside jaws, I can see 1,2 & 3 stamped in the bottom of the darker grey un-ground slot at the LH end of the jaws.

Nice looking chuck, but probably beyond the depth on my pocket. I have a £38 (delivered) Sanou K11 100mm 3 jaw sat waiting for the lathe to get a replacement inverter fitted & I thought that was pushing the boat out !

Nigel B.

I was just about to post this when I read your post there:

I take it all back, they are marked, just not very clearly:

well spotted!

[Dr_GMJNParticipant @dr_gmjn]

Posted by Mike Poole on 05/02/2021 17:28:41:

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

Thanks Mike, yes I understood that about 3 jaw chucks.

[SteviegtrParticipant @steviegtr]

Posted by Dr_GMJN on 05/02/2021 17:52:21:

Posted by Mike Poole on 05/02/2021 17:28:41:

There is a school of thought that says leave the register undersize and then the chuck can be centralised with a bit of judicious tapping and then finally tightened, the late Commander Barker who advocated this said he never had a chuck move after adjusting. Of course a heavy interrupted cut could test this and if it did move it may spoil a job. I have said a few times that I was taught to expect a 3 jaw scroll chuck to not be accurate or repeatable, if it is necessary to replace the job in the chuck and concentricity is important then use the 4 jaw independent and indicate the job true.

Mike

Thanks Mike, yes I understood that about 3 jaw chucks.

Unless you have a griptu 3 jaw. They are pretty good once adjusted. But not cheap to purchase. I found a new 100mm one for £550 so out of reach for most. I was lucky to have one given with the lathe when purchased.

Steve.

[DiogenesIIParticipant @diogenesii]

I think the numbers are stamped in one of the jaw's slots – there should be a four-figure serial no., and the jaw number er, somewhere close by..

Apropos tightening, I guess I mean, the emphatic one – I don't find there are too many degrees of tightening down with this size chuck – I don't seem to find much movement in the second or third pinions, and I don't insist on finding some – enough pressure to hold the work, but I don't wring it 'til it cries.

[Dr_GMJNParticipant @dr_gmjn]

So I got the chuck fitted – first time I’ve machined a backplate. I got it from Arc Euro – seemed pretty tough material and it was tricky to get a good finish. Anyway, after testing with a finger gauge I’m getting just under 0.0005” runout on the main body, and between 0.002” and 0.004” on a mill shank gripped with the jaws. As mentioned it depends which pinion is tightened:

The irony is, the 0.002” is identical to the best runout on my old chuck, but the worst in that is 0.005”. Of course the new one grips the workpiece all the way to the jaw ends, the old one I could see daylight for about 10mm from the ends.

The booklet with the chuck gives target runouts for the spindle and backplate spigot (which we’re ok), and goes on to say that runout on a test piece should be as per the spec. sheet for the chuck. Unfortunately there was no spec. sheet…

I’ve not tried rotating it on the backplate yet; might try tomorrow if I get chance. I suppose in theory I could find about another 0.0005” if I could rotate it to get rid of the body runout. Either way I think it should be ok.

[Dr_GMJNParticipant @dr_gmjn]

So to complete the thread – I tried the chuck in all three backplate positions, and tightening all three pinions a couple of times for each position. In the end I’ve ended up with consistently around 0.0005” runout with the best pinion in the best backplate position.

[Del GrecoParticipant @delgreco45469]

Good choice. I have the same chuck. Got mine from Myford.co.uk. They supplied a backplate too. I went with the one with the dividing holes. Never used them, but it'll be future proof if I want to use them in the future.

Re chuck removal, I have a large diameter Hex bar which I secure in the chuck, then use a spanner on it to loosen, after engaging the spindle lock on my Myford Super7. Works quite well for me so far with no issues.

So to summarise, great chuck. Slightly pricy from Myford, but I wanted to support a British company. Even if they're not fully made here any more!

[Dr_GMJNParticipant @dr_gmjn]

Posted by Del Greco on 09/02/2021 15:09:04:

Good choice. I have the same chuck. Got mine from Myford.co.uk. They supplied a backplate too. I went with the one with the dividing holes. Never used them, but it'll be future proof if I want to use them in the future.

Re chuck removal, I have a large diameter Hex bar which I secure in the chuck, then use a spanner on it to loosen, after engaging the spindle lock on my Myford Super7. Works quite well for me so far with no issues.

So to summarise, great chuck. Slightly pricy from Myford, but I wanted to support a British company. Even if they're not fully made here any more!

I admit that’s what I thought – made (or supplied!) from just up the road, and ‘reassuringly expensive’. Right or wrong I’ve got it, and it seems fine. A few burrs on the peripheral machined ring, but there we go.

I went for the Arc back plate based on looks alone – it seemed much better finished. I considered the Myford/RDG drilled version, but couldn’t really think I’d ever use it. As I said, the Arc backplate was pretty tricky to machine – lots of tool grabs even with new inserts. Tried all speeds too. Anyway, it’s done.

Well worth trying all 3 backplate positions and pinions, with different test piece positions at each setting. I was amazed at the difference in runout. I would never have known without this thread.

[BazyleParticipant @bazyle]

Be aware that one of our reputable suppliers is being honest about some lower quality chucks they are selling at a reduced price. This reminds us that chucks are just mass produced, tested, and the poorer ones sold off cheap but not marked up as secod or thrid rate. These are then sold by various barrow-boys who will not declare the deficiencies.

So if you get a new chuck off ebay from a non-mainline supplier check it immediately for concentricity with several sizes of stock. If the error is >5thou and moves around the chuck at different work sizes it is a substandard one and it is not the jaws or the backplate but potentially the scroll. Don't accept an 'exchange' from them as all their stock will be the cheap ones.

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