Hand Operated Chuck (HOC) : The production capacity
of a lathe is entirely a function of the chuck used, the gripping power
and the true running of the chuck.
A lathe with the excellently engineered
GMT chuck enhances the
productive capacity of the lathe which provides the answer to faster and
better guaranteed production.
CONSTRUCTION :
The conventional bevel gear and the scroll have been replaced by a
worm and wormwheel with three circular cams, to operate the jaws. The
chrome case hardened wormwheel-cum-camring ensures maximum resistance to
wear. The entire reaction of the clamping forces of the three jaws are
confined
in and taken up by the worm wheel-cum- camring and not by the chuck
body or component parts.
The chuck body and the wormwheel-cum- camring
are made from steel forgings, which provide the desired grain flow and
thus minimize distortion under the clamping forces. All the parts are
amply proportioned, made from high tensile alloy steels, hardened and
ground wherever necessary, to close limits of accuracy. The hard jaws
are provided with gripping serrations to grip the work piece firmly.
The normal dimensional variation in the
gripping diameter of jobs is taken care of by the adequate stroke of the
base jaws, thus avoiding frequent resetting of the top jaws.
On each circular cam, slides a chrome case-
hardened button with a groove of the same radius as the cam. This
provides a large pressure bearing area to the load transmitting
surfaces. The large bearing surfaces reduces the stress per unit area to
the minimum and completely inhibits any denting of the circular cam.
ADVANTAGES :
Because of the comparatively small number of well designed parts used in
the chuck, frictional losses are reduced to minimum. The worm,
wormwheel and the circular cam give the chuck an amazingly high
mechanical advantage resulting in a grip many many times more powerful
than that of a scroll chuck, for the same effort applied at the chuck
key. Appropriate cam rise, combined with worm drive, ensures self
locking action of the chuck over the entire clamping range and this
guarantees the safety of the operator.
The top jaws are positively located on the base jaw by serrations
ground after the jaws are case hardened. The top jaws can be quickly
reset for different sizes of work pieces by merely loosening two socket
head screws, shifting the jaw to the appropriate serration and
re-tightening.
Three Jaw chuck of sizes from 125 mm dia. to 315 mm dia. are offered with serrations of 1.5 x 60
o on the base jaws.
Sizes 400 mm dia. to 800 mm dia. are provided with 'V' Serrations of 3/32" x 90
o.
SOFT JAWS :
Soft Jaws are made from low carbon steel and
used for second operation. They are used for
gripping finished diameters and are supplied
as blanks. They are reversible, so that both
ends can be used.
The gripping diameters are to be machined in
position on the chuck. This will ensure true running of the job on soft jaws, within close limits.
