Retention Knobs & Pull Studs
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High-Torque Retention Knobs

Our high torque retention knobs provide longer life for your tools and machines. Because our unique design is solving problems in the industry by keeping tools perfectly aligned, this balanced retention knob design is catching attention from industry leaders around the world.

While standard retention knobs distort tool holders and move within the socket when in use, our high torque retention knobs balance dynamically from end to end. This improves the fit and maintains tight balancing tolerances long after initial installation.

This design reduces tool holder shank expansion up to 2 to 10 times, and significantly increases tool life.

Improve Durability, Extend Part Life, Reduce Distortion from Heat Treat

J&M High Torque Retention Knobs are

  • Made from hot rolled 8620H fine grain steel
  • Shot peened to relieve stress
  • Deburred with radius corners for better finish (finishes exceed international standards)

  • Laser-marked with month and year of purchase - track life span
  • Laser-marked with part number and serial number - trace part
  • Documented with written records on every manufacturing lot
  • Made in the USA with materials manufactured in the USA


  • Reduce Toolholder Expansion
  • Increase Rigidity
  • Improve Toolholder Balance


  • Increase Production
  • Increase Tool Life
  • Increase Feed Rates
To order High-Torque Retention Knobs, send an email to or call us. Simply use the part number from your present knob and we'll cross match it with the high torque knob.
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OUR STORY: New Generation High-Torque Retention Knobs

Using the first generation of our Taper Shank Test Fixture, we began experimenting with the actual retention knob design. We found that standard retention knobs inserted into the toolholder with as little as twenty foot/pounds of torque expanded the toolholder shank. Thanks to our newest design of the test fixture, we now know that the toolholder actually will begin to expand with as little as five to fifteen foot/pounds of torque.

To address this problem, we designed our High Torque Retention Knobs, which expand the toolholder shank two- to ten- times less than standard knobs (view full retention knob torque test details). This is even greater than initial test results that showed two- or three- times less expansion (see graph below).

Our retention knobs balance dynamically from end-to-end, resulting in a better fit within the toolholder. This makes it much easier to main tight tolerances after installation. Our design also includes a pilot on the high torque ANSI retention knobs, which significantly reduces breakage, especially when Bellville washers are not performing at full strength.

High Torque Retention Knob Performance Comparison
› Toolholder Expansion: High Torque Retention Knobs vs. Traditional Design.


The vertical axis on the graph on page 11 is based on a toolholder grind tolerance of 0.000080 inch. The greatest deformation reflected by the graph, at 80 ft. /lbs., is approximately 10 times the tolerance, or 0.0008 inch. While this number may seem miniscule, bear in mind that this discrepancy increases by a factor of 3.40 or 0.0027 inch. This number represents the distance that the toolholder moves out of the spindle due to the deformation of the toolholder. The resultant impact is that toolholders that measure 5.400 inches in length from the face of the spindle to the tool tip may run out up to 0.002400 inch T.I.R.

This same graph illustrates that the same toolholder, paired with a High Torque retention knob, may experience tool tip run out up to 0.000576 inch T.I.R., which is a significant difference. Simply stated, the two numbers represent the diameter the tool would be free to move forward and back or side-to-side. Therefore, by implementing lower torque pressure during retention knob installation, along with the selection of the best quality toolholder and use of a high torque retention knob instead of a standard knob, the distortion problem is solved.

It’s important to maintain retention knob installation torque at an acceptable level. Machines with 40 taper spindles normally have draw bar pressure of 2,500 pounds or less. Lateral force of 1.25 times the draw bar force, or 28 to 33 ft/lbs of torque, is adequate to ensure that the retention knob does not lose contact with the face of the toolholder.

John Stoneback, President
J&M Machine, Inc.

J&M Machine Inc. has manufactured retention knobs for 35 years. Test documentation on this subject is available at Questions call (440) 357-1234, fax (440) 357- 1129 or


» Download High-Torque
Retention Knob Brochure
» Read Current Articles
Expansion Problem Explained
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Toolholder Deformation Test
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Many manufacturers have machines which use different Retention Knobs or Pull Studs. These labels are used to identify the type of Retention Knobs or Pull Studs used on a machine.

You can stick them to a machine, put them in the tool cabinet, place them in the machine operation manual or for reference, place them in the rolodex card file. This way you insure that you order the correct Retention Knobs the next time you order.


  • Supplier's name
  • Part number
  • Phone number
  • Short description of Retention Knob or Pull Stud
  • Drawing of Knob / Stud
  • Warning statement
  • Order/lot number of shipment.

Extra labels with peel-off backing are supplied upon request.

Protect Retention Knob or Pull Stud Information by using laminated labels in oily areas. The next time you order 20 Retention Knobs, tell your distributor to include your four complimentary labels (3 peel-off labels and 1 laminated label for oily applications) with your next tooling package.

  • ANSI
  • JIS
  • ISO
  • DIN
  • CAT
  • BT40
  • P40T

J&M Machine is your complete Retention Knob / Pull Stud source to service your requirements. We carry over 500 different varieties of retention knobs manufactured to U.S., German and Japanese standards as well as a myriad of specials. J&M Machine is the leader in manufacturing certified, quality Retention Knobs and Pull Studs.