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<strong>Sure</strong>-Grip ® <strong>Power</strong> <strong>Chuck</strong> Safety and Technical Manual B-87Z<br />
Gripping Force Loss Due to Jaw Location<br />
The machining operations generate forces and movements which must be properly absorbed and transmitted by the<br />
power chuck. Gripping force is the main purpose of the chuck. This force is the arithmetic sum of the radial forces exerted<br />
on the workpiece by the chuck jaws.<br />
There are a great many variables which act on the clamping area of the jaws during a machining operation. To combine all<br />
these variables into one chart is not possible. The following formulas, tables and graphs in this chapter (and the methods<br />
for calculating them) are acceptable for the normal run-of-the-mill applications on well maintained and properly lubricated<br />
three-jaw chucks. The calculations are acceptable for normal as well as special applications. In the case of large and heavy<br />
top jaws, the centrifugal forces must be accurately calculated. The centrifugal force curves shown on pages 112-114 are for<br />
chucks with standard height pointed soft blank top jaws used in the mid-position of the master jaw. This blank top jaw will<br />
be heavier than one that has already been machined to accept a workpiece, therefore the results will be on the safe side.<br />
Gripping Force/RPM Diagram for 5" and 6" <strong>Sure</strong>-Grip ® <strong>Chuck</strong>s<br />
Upper Curve = Minimum Centrifugal Force of Top Jaw<br />
Middle Curve (best position to use any top jaw) = Mid-Position Centrifugal Force of Top Jaw<br />
Lower Curve = Maximum Centrifugal Force of Top Jaw<br />
NOTE: All Charts are based on calculated draw forces.<br />
Hardinge Inc. One Hardinge Drive, Elmira, New York U.S.A. 14902-1507 800.843.8801 www.hardingetooling.com<br />
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