GMT Hand Operated Chuck

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The conventional bevel gear and the scroll have been replaced by a worm and wormwheel with three circular cams, to operate the jaws.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.