Metallics G8HC344 Bolts 3/4-16 x 2-1/2 G8 HXBT St-zn (Box 25)

Fine thread. The G8HC344 is a 3/4-16 hex bolt, 16 threads per inch, which is UNF rather than the coarse 3/4-10 UNC. It will not thread into a coarse 3/4-10 nut or tapped hole, so match it to fine thread hardware. Shank outside diameter runs 0.7410 to 0.7500 inch.

The G8HC344 is a Grade 8 cap screw rated 150,000 psi minimum tensile and 130,000 psi minimum yield, hardness Rockwell C33-39. Grade 5 tops out well below that, which is why this one gets used in automotive and fleet work where the Grade 5 will not carry the load. It is medium carbon steel, heat treated, per AISI 1021-1045.

Head width across flats measures 1.100 to 1.125 inch, so a 1-1/8 inch socket or wrench is the fit. Across corners it runs 1.240 to 1.299 inch, which matters if you are working in a tight pocket or counterbore. The head is a standard hex.

The G8HC344 carries a zinc finish over steel, which handles indoor, shop, and sheltered equipment duty and gives moderate corrosion resistance outdoors. For sustained weather exposure, coastal air, or chemical washdown, zinc plated carbon steel will eventually surface rust and a hot dip galvanized or stainless fastener is the better call, keeping in mind stainless will not match Grade 8 strength.

These ship as a box of 25 bolts, and 25 count is the order minimum, so a single box is the smallest purchase. Other sizes and quantities in the G8HC and JG8HC series can be requested if your job needs a different length or diameter.

Both the Buy American and ARRA fields on the G8HC344 are flagged compliant, while country of origin is listed as China. On federally funded projects, bring both facts to your compliance reviewer, since domestic sourcing requirements vary by program and contract clause.

Bolts only. A box of 25 G8HC344 hex bolts contains the cap screws alone, so order fine thread 3/4-16 nuts and hardened washers separately. On a Grade 8 joint, use a hardened washer under the nut so the bearing face is not crushed when you torque to the higher clamp load this bolt allows.

Shank diameter on the G8HC344 is 0.7410 to 0.7500 inch, so a 13/16 inch hole gives normal clearance and a 25/32 inch hole a close fit. Do not drill to nominal 3/4 inch, the bolt will bind.

Head height is 0.455 to 0.483 inch, so allow about half an inch of standoff above the joint face plus room to swing a 1-1/8 inch socket. That also tells you the counterbore depth if the head needs to sit flush in a recess.

The packed box weighs 10.27 lbs and measures 7.25 by 6.75 by 3.25 inches. That is a one hand carry, which matters if you are staging multiple boxes for a rooftop unit or an equipment anchoring job.