Hex Cap Screw / Hex Tap Bolt (ASME B18.2.1)
Hex cap screws and hex tap bolts are the inch-series equivalents of metric hex bolts, manufactured to ASME B18.2.1. The two terms are used somewhat interchangeably in the industry — a hex cap screw typically has tighter dimensional tolerances and a washer face under the head, while a hex tap bolt is fully threaded and used in tapped holes.
Specifications
| Standards | ASME B18.2.1, ASTM A307, ASTM A449, SAE J429 |
|---|---|
| Grades | Grade 2, Grade 5, Grade 8, A307 |
| Diameter Range | 1/4" – 1-1/2" |
| Thread | UNC (Coarse), UNF (Fine) |
| Material | Low carbon steel (A307), Medium carbon (Grade 5), Alloy (Grade 8) |
| Surface Finish | Plain, Zinc plated, HDG, Yellow zinc, Black oxide |
Frequently Asked Questions
What is the difference between a hex cap screw and a hex bolt?
Technically, a hex cap screw has tighter dimensional tolerances on the head and shank than a standard hex bolt, plus a small chamfered washer face under the head. In day-to-day usage, especially in North America, the terms are often used interchangeably. ASME B18.2.1 covers both. For most applications they are functionally equivalent.
What does Grade 5 vs Grade 8 mean?
Grade 5 and Grade 8 are SAE J429 designations for inch fasteners. Grade 5 is medium-carbon steel, quenched and tempered, with a minimum tensile strength of 120,000 psi (for diameters up to 1"). Grade 8 is medium-carbon alloy steel, quenched and tempered, with a minimum tensile strength of 150,000 psi. Grade 8 is identifiable by 6 radial lines on the head; Grade 5 has 3 radial lines.
Need a quote on Hex Cap Screw / Tap Bolt?
Send us your specifications, target quantity, and destination port. We will respond within 24 hours with sourceable options and indicative pricing.
Get a Quote