Tc 9-524 fundamentals of machine tools

USING STEADY AND FOLLOWER RESTS
General
The steady rest consists of a frame and three adjustable jaws
which support the work, as shown in Figure 7-27. One
purpose of the steady rest is to prevent springing or deflection
of slender, flexible work; another is to furnish auxiliary
support for the work to permit heavy cuts to be made; a third
is to support work for drilling, boring, or internal threading.
The over arm containing the top jaw can be unfastened and
swung out of the way so that identical pieces can be removed
and replaced without adjusting the jaws.
Bearing Surface
A bearing surface must be provided for the steady rest jaws.
The bearing surface is usually machined directly on the work,
as shown in Figure 7-106. When the work is too small in
diameter to machine the bearing surface or shaped so that it
would be impractical to machine one, you can use a cathead to
provide the bearing surface. The cathead shown in Figure 7-
27, has a bearing you surface, a hole through, which the work
extends, and adjusting screws. The adjusting screws fasten the
cathead to the work. They are also used to align the bearing
surface so can use a cathead to provide the bearing surface so
that t is concentric to the work axis. Use a dial indicator to
ensure concentricity.
Setting up the Steady Rest
To setup the rest, first machine and polish the portion of the
work that is to be used as the bearing surface. Clean the
portion of the ways where the steady rest is to be mounted,
place the steady rest on the ways and clamp loosely. Open the
top of the steady rest and place the workpiece in the chuck
with the bearing surface over the adjustable jaws. Clamp the
steady rest securely to the ways. Close the top of the steady
rest and adjust the jaws to the workpiece. There should be
0.001 inch clearance between the jaws and the workpiece.
Tighten the locking screws on the adjustable jaws. Lubricate
the bearing surface generously with a heavy oil before turning
the lathe on. Proceed with the machining operation
Continuously watch the bearing surface and the adjustable
jaws to ensure a film of heavy oil is between them. As the
machining operation continues, also check the bearing surface
and adjustable jaws as when the workpiece heats up it will
expand, closing the distance between the jaws and the
workpiece.