Applications/ Advantages A pan head machine screw with a free-spinning lock-washer and flat washer manufactured as one assembly.

The washer / screw assembly makes this a locking screw with the helical washer providing the locking action and flat washwer distributing the load over.

MaterialSteelStainless Steel Screws-AlSI1006 - 1022 or equivalent steel. Steel Washers-Spl-lock:SAE 1060 carbon steel; Flat washer: SAE 1008 carbon steel.Stainless Screws- Class 304 stainless.
Stainless Washers- Class 304 stainless

HardnessSteel Screws-Rockwell B70 - B100 (Unhardened)
Steel Washers-Rockwell C38 - 46; Flat washer: Unhardened 

Tensile StrengthSteel. 60,000  psi minimum. No.4 SEMS screws shorter than 1/2"are not subject totensile testing. SEMS screws of diameters No. 6 to 10 indusive, which are shorter than 1/2" or 30 (where D is the nominal screw size in inches) are not subject to tensile testing. 

PlatingSee Appendix-A for information on the plating of steel SEMS.stainless sems are usually supplied with plain finish