Metallics G8HC75214 Bolts 3/4-10 X 2-1/4 G8 Hxbt St-Yzn (Box 25)

It's a 3/4-10 bolt, meaning 3/4 inch nominal diameter with 10 threads per inch, which is the standard UNC coarse thread for that size. Measured shank outside diameter runs 0.7410 to 0.7500 inch. Pair it with a 3/4-10 UNC nut; for a Grade 8 bolt in a structural or fleet application, match it with a Grade 8 (or higher) hardened nut and washer so the nut doesn't become the weak point.

Yes. The G8HC75214 is a Grade 8 cap screw rated 150,000 psi minimum tensile and 130,000 psi minimum yield, hardened to Rockwell C33-39. Grade 5 tops out lower, so Grade 8 is what gets specified in automotive and fleet work where the joint load exceeds what a Grade 5 can carry. For general non-structural mounting, a Grade 5 is usually enough and easier on your tooling. Note that hardened bolts are less ductile, so don't substitute Grade 8 into a joint engineered to flex.

No. This bolt is multi-origin and is flagged not Buy American compliant and not ARRA compliant, so it will not satisfy domestic-content requirements on federal, ARRA, or Buy America funded work. On those projects you need a domestically manufactured Grade 8 fastener with mill documentation. For private commercial, fleet, and MRO work the compliance flags are not a factor.

Across-flats head width measures 1.100 to 1.125 inch, so a 1-1/8 inch socket or wrench is the fit. That's the standard hex size for a 3/4 inch bolt. Use a 6-point socket on Grade 8 hardware if you're torquing it to spec, since the torque values on a 3/4-10 Grade 8 will round the corners of a worn 12-point.

These ship as a box of 25 pieces, and 25 each is the order minimum, so it's a full-box purchase rather than a loose-count item. Metallics does offer other sizes and quantities in the G8HC and JG8HC series on request if 2-1/4 inch length or a box of 25 isn't what the job needs.

The bolt is medium carbon steel with a yellow zinc finish. Zinc plating handles indoor, sheltered, and light outdoor exposure, but it is a sacrificial coating, not stainless: in standing water, road salt, coastal air, or chemical washdown it will eventually corrode. For permanently wet or marine service, go to a hot-dip galvanized or stainless fastener instead. Also keep in mind that Grade 8 strength is not available in standard stainless, so a stainless swap is a strength downgrade.

A 3/4-10 hex cap screw suits through-bolted or tapped-hole joints where you want a finished hex head you can torque from one side and a defined 2-1/4 inch length. Use threaded rod instead when the grip length varies or you need to field-cut, and a carriage bolt when the head has to sit flush and resist turning in a wood or sheet member. Where the load demands Grade 8 strength, a hex cap screw is the form that commonly carries that rating.

It's a heat-treated medium carbon steel cap screw made to AISI 1021-1045 material, finished at Rockwell C33-39. That hardness range is what delivers the 150,000 psi tensile minimum. The practical consequence on the job: don't weld it, don't flame-cut it, and don't re-plate it hot, because heat will pull the temper and drop the strength you bought it for.