What are Hex Cap Screws?

hex-cap-screws-group

Hex Cap Screws are fasteners featuring a hexagonal, six-sided, head with a washer face on the bearing surface and a chamfered point. Commonly used in construction and machine assemblies, hex cap screws are one of the most common fasteners used on the jobsite today. Specifications for hex cap screws are described under the ASME B18.2.1-1996 standard. Hex cap screw specifications include ASTM A449 & SAE J429: Grade 2, Grade 5 & Grade 8.

Hex Cap Screws are NOT Hex Boltshex-cap-screws

Mistaking a hex cap screw for a hex bolt is a very common occurrence, but the two fasteners differ in many ways, including the way they are used and installed.

  • Hex bolts are installed by turning a nut to tighten the fastener
  • Hex cap screws are installed into tapped holes by turning the head to assemble and tighten
  • Hex cap screws feature a washer face on the bearing surface and the chamfered point
  • Hex bolts have neither the washer face or chamfered point
  • Hex cap screws are commonly used for precision applications where a tight tolerance is required
  • Hex bolts are often used in the construction industry where the mechanical properties are more important than dimensional tolerances

Grades of Hex Cap Screws

Grade 2 Hex Cap Screwshex-cap-screws3

  • Often referred to as “hardware” quality, these fasteners are typically made of low carbon steel
  • Grade 2 fasteners are ideally suited for holding wood pieces together (in combination with appropriate nuts and washers) or general hardware use where higher strength is not required
  • There is no grade marking on the head of Grade 2 fasteners
  • Many manufacturers will put a distinguishing company identification on the head

Grade 5 Hex Cap Screws

  • Tempered Grade 5 fasteners are made of medium carbon steel
  • Grade 5 fasteners are quenched and tempered for the additional strength necessary for most automotive uses and other applications where strength is a moderate concern
  • The grade marking on the head of a Grade 5 fastener is three equally-spaced lines coming out from the center of the head
  • Manufacturers’ identifications are added for traceability

Grade 8 Hex Cap Screwshex-cap-screws7

  • Tempered Grade 8 fasteners are manufactured of medium carbon alloy steel for the most demanding applications
  • Grade 8 fasteners are then quenched and tempered to superior strength and hardness qualities
  • The grade marking on a Grade 8 fastener is six equally-spaced lines coming out from the center of the head
  • Manufacturers’ identifications are added for traceability

18-8 Stainless Steel Hex Cap Screws

  • The most popular type of stainless used in the production of fasteners
  • The composition is approximately 18% chromium and 8% nickel, thus the name 18-8
  • 18-8 stainless steel consists of several grades of stainless in this classification including 302, 303, 304 and 305
  • All of these grades of 18-8 stainless steel have good strength and corrosion resistance

316 Stainless Steel Hex Cap Screwshex-cap-screws6

  • 316 stainless steel is more corrosion resistant than 18-8, but also more expensive
  • 316 stainless steel is composed of approximately 18% chromium and 12% nickel with the addition of 2% to 4% molybdenum
  • 316 stainless steel also maintains its strength at higher temperatures than 18-8

410 Stainless Steel Hex Cap Screws

  • 410 stainless steel has approximately 12% chromium with no nickel
  • 410 stainless steel is not very corrosion resistant and is magnetic, but it can be heat-treated to become harder

Additional Hex Cap Screw Technical Specification Data Available

For a more in-depth look at hex cap screws, please visit our Hex Cap Screw Technical Specification Data page.

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