Testing Gage Checks for Toolholder Expansion


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Concerns over tooling cost containment and optimal tooling performance have led to the creation of JM Performance Products Inc.’s Taper Shank Test Fixture. 

A retention knob can expand the small end of a toolholder’s taper. This expansion can reduce contact between the toolholder and the spindle by 70 percent or more, the company says. This does not meet ISO 1947 angular taper tolerance (AT) specifications of AT3 or better. To avoid this problem, the company’s fixture checks toolholders for distortion caused by retention knob installation.

Design features include gages that read in increments of 0.0001" (ground to mirror a machine spindle), three top dial indicators that read height off the flange, and two side dials that read taper movement. The fixture is available in the following sizes: 30, 40, 45, 50 and 60 taper.

A test using the fixture can be performed on a toolholder with a retention knob already installed. After the fixture is fitted, indicators can be zeroed out for a base reading. The retention knob can then be loosened for a second reading, and the fixture will return an indication of whether the toolholder has experienced expansion.

An expanded toolholder does not need to be scrapped, the company says. The retention knob can be removed, and the toolholder will return to its original state. A high-torque knob such as the ones offered by JM Performance Products can then be used to tighten the toolholder to the correct torque specification.