Soft Jaws Question

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A few days ago, I said I had a job coming up where I used some cheap, quick and dirty aluminum soft jaw setup on the lathe. These are precision spacers, 16 Ra finish on one side, flat and parallel to 0.0002 and concentric to 0.0005. Thickness held to 0.0005. Here's the picture I promised. They all turned out within tolerance.

IMG_5210.JPG

IMG_5210.JPG
 
Tony Wells said:
A few days ago, I said I had a job coming up where I used some cheap, quick and dirty aluminum soft jaw setup on the lathe. These are precision spacers, 16 Ra finish on one side, flat and parallel to 0.0002 and concentric to 0.0005. Thickness held to 0.0005. Here's the picture I promised. They all turned out within tolerance.
Click to expand...

A pic is always worth a thousand words! ;)

Did you make them or are those ones commercially available?

M
 
I made them. I had some drops of 2024 AL and just drilled and counterbored them for the socket cap screws that normally hold the top jaws on. Nothing critical at all. I did not slot the back like the original top jaws so I could turn them to a virgin area to bore them to another size. When I remount them for a repeat job, I just snug the bolts, and then gently chuck down on the part to be machined. This roughly aligns them so I don't need to remove much material to true them up. Then I tighten the bolt. I usually find a socket or some short piece of bar to slip behind them in the master jaw to tighten down for boring. It's good to try to get something that allows them to be close to their original position. With the chuck tightened, bore just deep enough to hold the part if it's a thin washer like in the pic, and just slightly larger, so you can slip the part in....barely. Then when you remove the socket or bar, you can chuck right up on the part to machine.

Of course, this is just one example. The same principles can be used for ID chucking, but it's a little more involved to turn them, because you need to put pressure outward with the chuck, and finding a ring the right size is a little harder.
 
nice work tony i have never made anything that precision
for people that dont have removable jaws i seen a post about making a collet type of thing out of aluminum that fit in the 3 jaw chuck split 3 ways with shims in the slots, then he faced and cut the pocket for the thin part removed the shims and it looked like it worked well. like an emergency collet. thin parts are hard to work with. I have also cut a big thin washer on a face plate with double back sticky tape but it was a bugger to remove and clean
steve
 
WOW! I need to resize those pics. If you click for larger view..boy do you get one! Makes the setup look kinda trashy. Sorry about that.

Yeah, thin parts can be a pain to work with and require some ingenuity sometimes. Lots of ways to do things, some have advantages depending on what feature on the part is critical. Have to think it through.
 
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