Quote:
Originally Posted by PeterAllen
In which case I'll make a suggestion I hesitated to make before. I'm not sure about the alternator 'twin' pulley you show in the lathe and the 'single' one mounted to the alternator but it is useful to roll a thin piece of aluminium (or similar softish material) of uniform thickness around any delicate shape (e.g. threads) you are holding in the chuck jaws to minimise damage to the item being held.
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It's a very good suggestion Peter. You can see the marks from the jaws on the roughed out pulley. Most of the time I try to do the bulk of my machining while gripping the part on a section that will be machined off later. The twin pulley pictured was a failed attempt on one end and I just flipped the material around and machined the pulley out of the other end.
Depending on what I'm machining and how tightly it needs to be gripped I use strips of aluminium sheet between the jaws and the work piece. If I just need to take a light skim on something I'll often just grip it not so tight. Just don't make big cuts as you don't want the work piece to spin in the chuck.
Cheers