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Clamping sensitive parts in lathe

slow-poke

slow-poke

Ultra Member
I'm trying to speed things along with ballscrew upgrade. The end machining details for the standard DFU2005 ballscrews are not compatible with the bearing and spacing on my machine. So I'm considering ordering longer unfinished and then finish as required. The last thing I want to do is damage a brand new part by clamping it tightly in 3 jaw chuck. What are best practices for situations like this? Thin layer of copper over each jaw? If so how thick etc. Usually I'm just clamping some rough piece of stock not precision finished parts.


I actually already have an almost suitable ballscrew for the Yaxis, the snout is just a couple of inches too short. If someone is capable of turning a 2" extension with internal metric threads I could use what I have, it would thread onto the thread shown below and need to be 5mm larger in diameter (outside)

142DDB2C-4B11-495B-991B-FA182FE9207A.jpeg
 
Brass or copper shims in a 4 jaw chuck allows you to dial it in. Thats how I'm doing it. I'm doing all my work on the floating end (less work) and will grind if required (have an electric die grinder that will be mounted onto the cross slide if needed).
 
Flattened copper pipe over here as well, you can form the copper to fit around the jaw so your not fumbling around trying to hold 3 pieces of shim and tighten the jaws at the same timr
 
I use cut strips of pop cans, electrical tape, flattened copper pipe, epoxy sleeves, and collets as appropriate to protect finished surfaces. They all work.
 
Above comments are all good. I’ll add 6J chuck and soft jaws cut to size. Also, you don’t have to grip very tightly (chucks hold well), don’t grip tighter than what it takes to do the job.

The image of bent chuck keys is one of my pet peeves. I don’t get it that a real man has to show he strong enough to bend the handles on the chuck keys, or put a longer handle on. The target torque identified in the chuck user guide is not crazy high (Bison 6” 3J, 120NM or 88 ft-lbs max). Not really your question - just felt like venting a bit.
 
Proxule said:
Is that a dual ballnut setup I see?
Click to expand...
Yes, seems to make sense while it's all apart. I'm strongly leaning towards ac servos this time, the cost over steppers has dropped considerably (Leadshine/StepperOnline). Servo tuning might prove interesting, my university control theory is a distant memory.
 
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