Need Help!- Sieg C3 marking the Workpiece

[djh82uk]

Hi Guys

Just a question, I have a Sieg C3 Mini lathe with the standard 3-jaw chuck, i work mostly with aluminium. Now say I need to work on both ends, I get one end as I want it, take the piece out, flip it around and put the nicely finished part in the chuck, I play around for ages with a dial guage indicator to get the damn piece to be as near aligned as it was (off topic but is there a better way to do this?), then I start working on the other end, but if I don't tighten the chuck then the piece can wobble or slip, and if i tighten it too much I get teeth marks on the piece.

Now I know you can get soft jaws for some chucks but I have never seen any for the C3, anyone seen any that fit?

Also is it worth getting a chuck that comes with both types of jaw?

Are they worth it or do they make the workpiece much more difficult to re-align after flipping it over?

Any help appreciated

Thanks

DJH

[escott76]

First things first, with a 3 jaw self centering chuck you aren't going to get it aligned all that well. The scroll on the chuck simply isn't that accurate or repeatable. If you want a truly centered part you need to use a collet setup or a 4 jaw (or a set-tru style, but that's another story).
You could put in some sacrificial pieces between the chuck and the workpiece. Heavy paper, thin plastic, or soda can material can all work well. You can also make a "false collet" by slotting and boring a sacrificial part to just the ID you want to fit the OD of the part. Mark it so you put it back in the chuck the same way and you will kill both birds with one stone. Centered as you bored it in the lathe itself, and if it's cut to the right size you'll grip with no issues.
Another option might be to do whatever you want to the part such as boring, internal threading, basically anything you need done in the inside of the part in one opp. Then mount the part between centers and turn the OD. That would of course depend on the part design itself.

[Twmaster]

Basically what escott76 said about the repeatability of the scroll chuck.

However, you know that thin magnetic material like refrigerator magnets? Cut three small slivers that just fit in the jaws of the chuck. LEave the finished surface facing the work. Tighten. No mars to be found.