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Myford ML7 Chucks - Which one?

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Dr_GMJN07/02/2021 22:04:44
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1225 forum posts

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_GMJN08/02/2021 23:11:15
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1225 forum posts

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 Greco09/02/2021 15:09:04
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13 photos

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_GMJN09/02/2021 19:57:02
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1225 forum posts
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.

Bazyle09/02/2021 20:29:45
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6087 forum posts
221 photos

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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