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Online literature contains the most current information available.
Type S, SS, CLS, and CLSS nuts provide load-bearing threads in thin sheets with high pushout and torque-out resistance.

Type SP, PEM 300® nuts provide strong load-bearing threads in stainless steel sheets as thin as .030”.

Types S / SS are recommended for use in steel or aluminum sheets HRB (Rockwell "B" scale) 80 or less and HB (Hardness Brinell) 150 or less.

Type SP is recommended for use in stainless steel sheets HRB (Rockwell "B" scale) 90 or less and HB (Hardness Brinell) 185 or less.
Unit of Measure

Thread Size

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

Thread Code

N/A 0428

Shank Code

N/A 1

A (Shank) Max.

N/A .054 in a1383.jpg
Rec. Min. Sheet Thickness1 N/A .056 in

Hole Size in Sheet + .003 - .000

N/A .344 in

C Max.

N/A .343 in

E ± .010

N/A .440 in

T ± .010

N/A .170 in
Min. Dist. Hole C/L to Edge2 N/A .34 in
For Use in Sheet Hardness3 N/A HRB 80 / HB 150 or less

Thread Specification

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

Fastener Material

N/A Heat-Treated 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.
  • 2 To minimize sheet distortion and maximize product performance, use a centerline-to-edge value greater or equal to the value specified.
  • 3 HRB - Hardness Rockwell “B” Scale. HB - Hardness Brinell.