Jam Nuts

Jam nuts are thin hex nuts, roughly half the height of a standard nut. They are used to lock another nut in place, set position on threaded rod, or fit where a full-height nut won't. Tightened against a standard nut, the two "jam" together to resist loosening. We stock jam nuts across grades and materials.

How Jamming Works

A jam nut is run down first, then a standard nut is tightened against it (or vice versa). As the two are torqued together, their threads bind in opposite directions against the bolt, wedging the assembly and resisting vibration loosening. Correct order matters — the thinner jam nut typically goes on first, against the work.

Other Uses

Beyond locking, jam nuts set and hold position on threaded rod and shafts, act as spacers in tight assemblies, and fit shallow clearances where a standard nut is too tall. Their low profile makes them versatile in adjustment mechanisms.

Materials and Finishes

Grade 2 and Grade 5 steel with zinc plating for general and higher-strength use. 18-8 and 316 stainless for corrosion resistance. Match the jam nut material and grade to the primary nut and bolt.

Dimensional Standards

Inch jam nuts conform to ASME B18.2.2; metric thin nuts to DIN 439 / ISO 4035.

Selecting the Right Jam Nut

Match thread size and pitch to the bolt and primary nut. Choose grade and material to match the joint. For locking, install in the correct order and torque properly — note that two jammed nuts provide good vibration resistance but a dedicated prevailing-torque lock nut may be better for critical joints. Verify clearance for the reduced height.

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