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Socket Head Cap Screw Technical Information Guide


Grainger Editorial Staff

Socket head cap screws feature a hexagonal center recess in the head for tightening with an Allen wrench or hex key. With no sideclearance restrictions, they can be placed close together and are ideal for assemblies with close tolerances.

Standard socket head cap screws typically supply higher tensile strength, better yield strength, and more shear strength than equivalent sizes of hex head cap screws; yet they require less counter-bore because they are internally wrenched.

 

TYPES

Standard Head

Features a relatively high cylindrical head with a recessed hexagonal socket. Used where maximum tensile strength is essential.

 

Button Head

Dome-shaped head has wider hex socket and lower profile than standard. Ideal for lighter applications with low limited clearance where loading capacity is not critical.

 

Flange Head

Projecting collar around bottom of head acts like a washer, dispersing the load on the bearing surface. Used when a wider bearing surface or a more finished appearance is desired, and with thinner materials.

 

Low Head

Head height is 50% lower than standard size; socket size is smaller. Used in thinner materials and where clearance is too limited to use a full-height cap screw. Cannot withstand the same preloads as standard socket head cap screws.

 

Self-Locking

Features a nylon patch bonded onto the threads as a locking element. Holds fastener firmly in place and prevents loosening from vibration.

 

Vented Head

A small hole drilled through the entire length of the cap screw allows gas and fluids to vent.

 

MATERIALS

Stainless Steel—contains a minimum of 12% chromium for exceptional resistance to extreme environmental conditions. Properties are highly anticorrosive. Not affected by scratching; however, not as strong as common alloy steels. May be mildly magnetic.

18-8 Stainless Steel—contains approximately 18% chromium and 8% nickel. Provides excellent protection against rust and corrosion. The material of choice for prolonged outdoor use or exposure to salt spray and chemical fumes. May be mildly magnetic. Comparable to ASTM 300 Series and ISO A2.

316 Stainless Steel—contains a minimum of 2% molybdenum for superior corrosion resistance and reduced risk of pitting in extreme environments. Is nonmagnetic and can't be heat treated or hardened. Comparable to ISO A4.

Steel—the most common fastener material. Available in these types:

  • Alloy Steel contains enough alloying elements (other than carbon) to affect the fastener's properties; generally more responsive to heat and mechanical treatments.
  • Plain Steel (or Carbon Steel) contains only carbon and residual amounts of any other impurities. It is magnetic and malleable and can be either cast or wrought.

Zinc-Plated Steel—provides good to excellent rust and weather resistance.

 

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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