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Welcome to our Retention Knob Torque Testing studies website. We’re extremely excited to share our findings with you. We think that you’ll be as amazed as we are by the test results.

J&M Machine's Standard & High Torque Retention Knobs
J & M Machine, Inc. has been making retention knobs for more than 30 years. Over this 30 year span, many articles on taper shank tools, speculating about the cause of the marks on the tool shanks, have passed through our hands. Some tool manufacturers have recommended using 20 ft/lbs maximum torque when installing retention knobs in their toolholders as a way to eliminate the marks (shown on the toolholder below).

Marks on Shanks & our Taper Shank Test FixtureWe know that the average employee installing new tools in toolholders is going to exceed that recommended 20 ft/lbs. In reality, after many tool changes, the force of the draw bar pulling on the retention knob will compress the 60-degree thread faces of the retention knob and the toolholders enough to loosen the retention knob.

We designed and built the “Taper Shank Test Fixture” (patent pending) which measures the growth of the tapered shanks of toolholders (shown left). Using this fixture, we tested popular brands of retention knobs and toolholders for sale in the United States, at different torque settings. With this patent pending “Taper Shank Test Fixture”, we were driven to design a retention knob that when tightened to the same torque settings as standard retention knobs, causes two times to four times LESS expansion and distortion than a standard retention knob.

The test results from J & M Machine, available in PDF format, can be viewed by selecting the TESTING DATA tab. For information on Certifications for equipment used in these tests, go to EQUIPMENT CERTS.

We will be adding more tests as they become available, so please come back and visit this site often. We’d appreciate your feedback, so please leave your comments on the COMMENTS page.

E-mail us with your questions to: info@retentionknob.com and we will reply directly to you.

Thank you for your interest in J&M Machine, Inc. We hope you find this information informative and exciting!

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