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Box of 100 black oxide alloy steel socket head cap screws, coarse thread

Kerr Lakeside

Kerr Lakeside 31C275KCS 5/16-18 x 2-3/4 in. Socket Head Cap Screw Black Oxide 100 Pieces

SKU CH-B152-Q362G

Black oxide alloy-steel socket head cap screws, 5/16-18 UNC coarse thread, 2.75 in. length with 1.125 in. partial thread, RC 38-43 hardness, 180000 psi tensile strength.

  • Meets ASTM A574 & ANSI B18.3 standards for critical fastening
  • 180,000 psi tensile strength handles extreme loads
  • Black oxide finish resists corrosion in harsh environments
  • Hex socket drive enables high-torque installation
  • 100-piece pack covers large-scale assembly projects

Socket Cap Screws for High-Strength Assembly

These Kerr Lakeside socket head cap screws meet ASTM A574 and ANSI B 18.3 standards for critical fastening. The alloy steel body reaches Rockwell hardness 38-43 with a minimum tensile strength of 180000 psi. Each fastener uses a 5/16-18 UNC coarse thread and a hex drive for secure installation. The pack contains 100 pieces for production or maintenance use.

Black Oxide Finish and Material Properties

The black oxide coating provides mild corrosion resistance and a low-reflectivity surface. Alloy steel construction delivers the rated hardness and tensile strength without additional surface treatments. Right-hand thread orientation follows standard assembly practice. Partial thread length of 1.125 in. leaves an unthreaded shank for shear resistance in structural joints.

5/16-18 UNC Coarse Thread with 2.75 in. Length

The callout size defines fit: 5/16 in. nominal diameter, 18 threads per inch, 2.75 in. overall length. Thread length is fixed at 1.125 in., so verify grip range before ordering. Buyers needing a different thread pitch, longer thread engagement, or a full-thread fastener cannot use this part.

How it compares

Measured against everything we stock in Bits, Hole Saws & Accessory Kits, at today’s prices. Recalculated every night.

Price $32.99
Pricier than about 55% of the 5,493 comparable items (median $27.99).

Specifications

Product
Brand nameProspect Fastener

Questions about this item

How do I install a 5/16-18 x 2-3/4 in. socket head cap screw and what step is commonly missed?

Use a 5/16 in. hex key to drive the head; the step often missed is confirming the 1.125 in. thread length engages fully before the unthreaded shank bottoms out.

What maintenance or replacement will these alloy steel black oxide screws need later?

Inspect the black oxide finish for corrosion and check threads for galling; replace any screw showing rust, stripped hex drive, or elongated threads under the 180000 lbs/in. tensile rating.

What limit appears first when these screws are under sustained load?

The 180000 lbs/in. tensile strength is the first hard limit; sustained tension approaching this value risks permanent stretch or fracture of the alloy steel shank.

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