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Locking and Non-locking Threads
These fasteners provide load-bearing threads in thin sheets and permit up to .030” adjustment for mating hole misalignment.

The self-clinching feature offers fast and simple assembly. The fasteners are squeezed into prepared holes using any standard press. The sheet remains flush on one side, and the fastener is permanently locked in place.

Extra strength and support in assembly is obtained by the threads of the floating nut extending fully into the retainer shank (a unique PEM feature). A self-locking version of the fastener is also offered. Thread locking torque performance is equivalent to applicable NASM25027 specifications.

Non-locking Type A4 and self-locking Type LA4 fasteners provide load-bearing threads in stainless steel sheets as thin as .038” with hardness up to HRB 88 on the Rockwell “B” scale.

Many PEM Type AS and AC self-clinching floating fasteners correspond to sizes in US NASM45938/11 specifications. Check our web site for a complete Military Specification and National Aerospace Standards Reference Guide (Bulletin NASM).
Unit of Measure

Thread Size

 N/A .250-28 (1/4-28)

Thread Type

 N/A Self-Locking a1369.jpg

Thread Code

 N/A 0428

Shank Code

 N/A 2

A (Shank) Max.

 N/A .054 in a1368.jpg

Min. Sheet Thickness

 N/A .054 in

Hole Size in Sheet + .003 - .000

 N/A .515 in

C Max.

 N/A .514 in

D Max.

 N/A .510 in

E ± .015

 N/A .600 in

T2 Max.

 N/A .310 in

Min. Dist. Hole C/L to Edge

 N/A .420 in

Float

 N/A .015” minimum, in all directions from center, .030” total

Fastener Material

 N/A Steel

Fastener Materials - Retainer

 N/A Heat-Treated Carbon Steel

Fastener Materials - Nut

 N/A 300 Series Stainless Steel

Retainer Finish

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

Nut Finish

 N/A Black Dry-film Lubricant
For Use in Sheet Hardness1 N/A HRB 70 / HB 125 or Less

Thread Specification

 N/A Internal, ANSI B1.1, 2B

CAD Supplier

 N/A PennEngineering® (PEM®)
  • 1 HRB - Hardness Rockwell “B” Scale. HB - Hardness Brinell.