Best "Value" Lathe Chuck, & Backplate Interchange?

If the problem is in the cams then the chuck will be loose when they stop turning.

Enginörd doesn't realize his spindle nose is worn - the backing plate is supposed to need a light mallet strike to remove it from the taper.
 
Pulled out the cam lock cams, and there is some wear and burrs. The groove on the cam, for the retaining mechanism, is too narrow on one of the cams for the retaining plunger to fit down into the groove. I don't think this will cause the issue in question, but it does speak to the poor machining of the part, because I'm pretty sure it's been this way since new. On the search for new cams now...

Edit: it seems that there is an ISO standard for these parts. MSC sells USA made cams for $36 each. That's looking like my best bet at this point. It may not solve the problem, but it seems like a worthy upgrade.

Edit 2: bought a new set of cams. Hoping this will improve the action of the mechanism. Of course, that assumes they fit, that is. I checked the dimensions of the ISO standard, against my existing cams, and the dimensions are close, so fingers crossed.
 

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Got the new scroll cams, and they look really nice. Much better made than the originals. I'm not expecting them to solve the problem, but getting closer.
 
I spoke too soon. Look at how poorly the hex is machined compared to the old cam.
 

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Apparently, the same cams MSC sells are being sold by various other companies as well. They advertise them as "Made in USA". Is that a brand? Google doesn't turn up anything on this.

Figured out that Grizzly sells cams. A $10 version, from one of their lower end lathes, and some $14 jobbies from their South Bend Heavy 10 machine. I bought those. They are almost 3X cheaper than the MSC cams. I should have researched more before purchase.
 
Well, the Grizzly camlocks have a much better hex shape than the "Made in USA" pieces. Those are headed back to MSC. In the end, though, while the cam action is definitely smoother, I still can't get the PM collet chuck to seat on the spindle taper.

Could the PM backplate be improperly machined? There appears to be chatter in the ground surface, but is that enough to cause this problem?

I put a fine cut jewelers file on the spindle taper, trying to feel for any nicks and what have you, but there aren't any. I'm having a hard time figuring out how to move forward at this point.

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Is this normal? PM camlock stud on the left...

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Nesse1 said:
Is this normal? PM camlock stud on the left...
Click to expand...
The one on the left looks like my Pratt-Bernurd studs. so they seem Okay... the one on the right looks far less like what I'm expecting.
 
Dabbler said:
The one on the left looks like my Pratt-Bernurd studs. so they seem Okay... the one on the right looks far less like what I'm expecting.
Click to expand...

Interesting. The stud on the right is from my 3 jaw backplate, which mounts up nicely.

I think the issue is that the spindle taper shape doesn't match that of the female taper in the backplate.

I found an older thread here, where it was suggested that this is not unusual. Fix involved some light skimming of the female taper. Easier said than done...
 
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