4-40 Flat Head Socket Cap Screws

#4-40 flat head socket cap screws in USS coarse (UNC) thread, made from heat treated alloy steel with a black oxide finish. We stock 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 7/8", 1" lengths. They take a 1/16" hex key. Length is measured overall, including the head.

Specifications

Size: #4-40 (USS coarse)
Lengths: 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 7/8", 1"
Hex key: 1/16"
Tap drill: #43
Material: alloy steel, ASTM F835
Finish: black oxide
Strength: 145,000 psi minimum tensile strength (ASTM F835)
Head: 82° countersunk

Common Uses

Flush mounting
Machine plates and slides
Fixtures

FAQ

What hex key fits a #4-40 flat head socket cap screw?
A 1/16" hex key (Allen wrench).

What tap drill do I use for #4-40?
Use a #43 drill for a standard 75% thread.

Are button head socket screws as strong as socket head cap screws?
No. Button and flat head socket cap screws are made to ASTM F835, with a minimum tensile strength of 145,000 psi in 1/2" and smaller and 135,000 psi over 1/2". Their smaller socket also takes less torque, so use a socket head cap screw for high loads.

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