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PEM® S-RT™ free-running locknuts are free-running until clamp load is induced. A modified thread angle on the loaded flank provides the vibration resistant locking feature.
  • Screw turns freely until a clamp load is applied.
  • Resistant to vibrational loosening.
  • Back side of panel is flush or sub-flush for screw installation.
  • Locking feature reusability is not affected by number of on/off cycles.
  • Uses same mounting hole and installation tooling as standard S™ nut fasteners found in PEM® Bulletin CL.
Unit of Measure

Thread Size

N/A .313-18 (5/16-18)

Thread Code

N/A RT0518

Shank Code

N/A 1

A (Shank) Max.

N/A .054 in RT-Drawing.jpg
Rec. Min. Sheet Thickness1 N/A .056 in

Hole Size in Sheet + .003 - .000

N/A .413 in

C Max.

N/A .412 in

E ± .010

N/A .500 in

T ± .010

N/A .230 in

Min. Dist. Hole C/L to Edge

N/A .38 in

For Use in Sheet Hardness

N/A HRB 80 / HB 150 or less

Thread Specification

N/A Modified thread form on loaded flank. Will accept a maximum material 6g screw.

Fastener Material

N/A Hardened Carbon Steel

Standard Finish

N/A Zinc plated per ASTM B633, SC1 (5µm), Type III, colorless

CAD Supplier

N/A PennEngineering® (PEM®)
  • 1 For maximum performance, we recommend that you use the maximum shank length for your sheet thickness.