mechanicalmagic wrote:Now for the style of the chuck, get REMOVABLE top jaws. (aka two piece jaws.) <snip>. If you have removable top jaws, you can make "soft jaws" from soft steel or Aluminum.
Very good advice, Dave. In fact, that's advice worth its weight in gold.
Soft jaws are the silver bullet of holding---yet, sadly, often disregarded by the home shop.
Soft jaws are not strictly a production tool----they lend themselves very well to holding objects that, otherwise, can be difficult, if not impossible, to hold while machining. If a small selection of jaw configurations are created at the outset, there is generally a set that can be altered slightly to fit almost any occasion. Couple that with the use of an adjustable spider and you can alter jaws by removing almost nothing when fitting a part, prolonging the useful life of the jaws considerably.
One more suggestion. If steel is used for jaws instead of aluminum, it's perfectly acceptable to weld new material on well used jaws.
Welding on aluminum jaws isn't as desirable due to the fact that the weld process will eliminate the heat treat (artificial aging) of the aluminum. It can be restored only be solution annealing the jaws, then re-aging. That is generally beyond the ability of the home shop, and may be more involved than desirable.
I have soft jaws made of steel and aluminum. If aluminum is your choice, 7075-T6 has tensile strength that rivals mild steel. 6061-T6 is also acceptable.
Properly fitted, soft jaws hold without distortion or marking. They are an excellent choice when finish machining objects that must have a good appearance.