Metallics JG8HC66 Bolts 1/2-13 x 2-1/4 G8 HXBT St-zn (Jar 25)

It is a 1/2-13 bolt, meaning a 1/2 inch diameter body with 13 threads per inch, which is the standard UNC coarse thread for that diameter. Any 1/2-13 coarse nut threads onto it. For a Grade 8 joint you want a matching hardened nut rather than a common Grade 2 nut, so the nut is not the weak link.

Yes, and that is the whole reason to specify it. The JG8HC66 is rated 150,000 psi minimum tensile and 130,000 psi minimum yield, with a hardness of Rockwell C33-39. Grade 5 runs lower on both counts, so Grade 8 is what gets used where a Grade 5 cap screw will not carry the clamp load, typically automotive, fleet, and heavy equipment mounting.

The bolts ship in a jar of 25, and 25 each is the order minimum, so a jar is the smallest unit. Metallics lists other sizes and quantities as available by request if 2-1/4 inch length or a 25 count does not suit the job.

The JG8HC66 is medium carbon steel with a zinc finish. Zinc plating handles indoor service and incidental moisture well, but it is a sacrificial coating, not stainless. For continuous outdoor exposure, washdown areas, or coastal sites, expect eventual rust at the heads and plan on hot-dip galvanized or stainless fasteners instead. Note also that high strength plated bolts should not be used where hydrogen embrittlement or heavy corrosion is a concern in a safety-critical joint.

Metallics flags the JG8HC66 as compliant for both Buy American and ARRA. Country of origin is listed as multiple, so if your project submittal requires a specific mill or country certification on the fastener, request documentation for the lot you receive.

Material is medium carbon steel to AISI 1021 through 1045, quenched and tempered to hit the Grade 8 hardness band of Rockwell C33-39. That heat treatment is what gives it the strength, which is also why you should not weld, re-heat, or re-cut a Grade 8 bolt in the field.

The hex head measures 0.428 to 0.438 inches across the specified width dimension, so size your socket to the head you have in hand rather than assuming. Grade 8 hardware is normally torqued high, so use a six point socket and a torque wrench rather than an open end wrench to avoid rounding the corners.