[How-To] Hold a knurled part in a lathe chuck?

[ChazzC]

Yes, you can print 3d ER32 collets
For goofs, i printed 1 hexagonal collet, 5/16” and 1 square 3/8” collet
Both were found on thingyverse

Thanks, I’ll give them a try

 

[Inferno]

I have had parts that I need to knurl first in the order of operations then need to hold them in the chuck to do more work on it and not damage the knurling.

I have been using layers of paper towel wrapped with a thin brass piece and it works fairly well, sometimes need to adjust if it is not centered well,

Is there something else to wrap with or a different method?

I haven't read the other replies but in shop class, back in the late 70's my machine shop teacher showed us that to protect knurled (or machined) surfaces when turning from the finished end, all we needed was a softer metal with a thick piece of paper or cloth. Just need enough shims for each pad that comes into contact with the part. We, typically, used brass shims because we had a lot of those in the shop.

 

[Larry$]

First choice is always a collet, 2nd is a couple of wraps of aluminum can. 3rd is turning an aluminum bushing and splitting it. List in order of least time.

 

[BGHansen]

I haven't done it myself, so it's just a concept. Guys wrap vise jaws with copper to keep from damage the surface of parts. How about wrapping the lathe jaws with sheet copper or aluminum flashing? Copper pipe as Doug Gray mentioned or a cut up aluminum can may work too.

I've wrapped parts with duct tape with some success. I've tried masking tape but really tight chuck jaws can bite through.

Bruce

 

[Cadillac STS]

The recent project is 1 and 1/2 aluminum knurled so I think any hard surface would mar them.

I was using brass shim all the way around lined with a good amount of paper towel and that worked but I think the paper is not always consistent or the squeeze on the paper is not consistent because the run out is pretty bad sometimes and needs adjustment.

Thanks for all the replies. I think it would be best to try a custom collet from nylon, close fit and thin walled without a slit to see if the vice jaws bear down evenly.

 

[francist]

Just a thought if you don't want to use fresh material -- if the dimension is close to nominal some PVC water pipe may work just as well and lots cheaper. Making your own out of the nylon would probably get you more accurate though.

 

[pontiac428]

The reason I like 10 mil tape (too cheap for 20 mil) is that it is manufactured to one spec: Thickness. It might not be as consistent as shim-in-a-can, but it works great when you need those "sweet lips" to hold your part without marring.

 

[epanzella]

If I have to machine a knurled part that doesn't require much accuracy I just use making tape. The problem with that is getting the OD the same at the front and back to avoid cutting a taper or non parallel feature. If it has to be accurate I machine nylon or polyurethane bushings. I have plenty of these chunks around as I save all my old worn out boat trailer rollers.

 

[Cadillac STS]

A bushing made from nylon worked great. Firm hold. No slit in the bushing. Knurl protected.

 

[darkzero]

Fine looking knurl. I can't stand the look of a double tracked or a crooked off axis looking knurl.