Replaceable jaws made from soft material so they can be cut to match the part's shape, gripping odd profiles, finished surfaces and thin walls without marking or distorting them. Lathe soft jaws are bored while clamped on a ring or plug at the same pressure used for the part, which makes them run true to the spindle. Once cut, they are labeled and stored for the next run of that job.
Cut a new set of soft jaws for the second op, the finished OD can't take a mark from the hard jaws.
Bore lathe soft jaws while they are clamped on something at running pressure, or they will not run true once they grip the part.
Also heard as
- softies
- machinable jaws
Related terms
Fixturing
The design and use of fixtures that locate and clamp parts the same way every time.
Four-jaw
Shop name for an independent four-jaw lathe chuck, each jaw adjusted separately to center or offset work.
Collet
A slotted, tapered sleeve that squeezes evenly around a tool shank or bar stock to grip it accurately.
Parallels
Matched pairs of ground steel bars used to raise a part in the vise to a known, level height.