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High Torque© High Strength (HTHS) retention knob, CAT 50, 1"-8; 45°, Coolant through, O-Rings included; Made from 9310H steel, 40% stronger; Replaces JM31251A

Retention Knob Information and Installation (PDF)

Retention Knob Installation Video

Category: Retention Knobs
Thread Size: 1.00-8
Angle: 45
Knob Diameter: 1.140
L1 Length: 0.7000
L2 Length: 1.000
Flange Thickness: 0.200
Hole Diameter: 0.390
Knob Side O-Ring: PS-10A
Neck Diameter: 0.820
Pilot Diameter: 1.030
Shoulder Diameter: 1.400
Wrench Flat Diameter: 1.183
Socket Part #: RKW50M
Number: JM31251AHTHS
Country of Origin: USA

This knob is a replacement for the following parts:

ManufacturerPart Number

* Retention knobs are not interchangeable. Machines are only given as a reference, JMPP makes no guarantee this is the correct knob for your machine. Please call us at 1-800-322-7750 or email for knob identification help.

WARNING: The steel alloy used in this product contains chromium and nickel. This product can expose you to chemicals including chromium and nickel, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to