Metallics G8HCF83 Bolts 5/8-18 x 3 G8 HXBT St-zn (Box 25)

Yes, and that is what it's built for. The G8HCF83 is a Grade 8 cap screw rated 150,000 psi minimum tensile and 130,000 psi minimum yield, which is a step up from a Grade 5 in the same diameter. Metallics describes it as a medium carbon steel bolt, heat treated, used in automotive and fleet work where Grade 5 tensile isn't enough. A Grade 8 can go where a Grade 5 was specified; the reverse is not true.

Not reliably. The shank outside diameter runs 0.6170 to 0.6250 inches, so at the top of tolerance it is a full 5/8 inch and will bind in a clean 5/8 hole. Standard practice is to drill 11/16 inch for a 5/8 bolt so you have clearance for the shank and for coating thickness on the zinc plating.

Fastener length is 3 inches measured under the head, so the 3 inches is your usable stack of material plus washers plus nut engagement. Head height (27/64 inch) sits on top of that and is not part of the 3 inches. For a steel-to-steel bolted joint, size so the nut fully engages and threads run at least flush with the end of the nut.

The G8HCF83 is steel with a zinc plated finish, which handles indoor and sheltered conditions and incidental moisture. Zinc plating is a thin sacrificial coating, not hot dip galvanizing, so for continuous outdoor exposure, washdown areas, or coastal sites you want a hot dip galvanized or stainless fastener instead. Note also that Grade 8 bolts should not be hot dip galvanized after the fact.

No. It is the hex bolt only, 25 to a box. You order the nut and washers separately, and for a Grade 8 bolt you want a matching Grade 8 (or Grade C) hardened nut and hardened washers, not a Grade 2 nut, or the nut becomes the weak point in the joint.

These ship 25 to a box, and 25 is the order minimum, so a single box is the smallest purchase. Metallics notes other sizes and quantities are available by request if you need a different length or diameter in the same Grade 8 hex bolt line.

Material is medium carbon steel to AISI 1021 through 1045, heat treated to Rockwell C33-39. That hardness range is what carries the 150,000 psi tensile rating. It also means the bolt is harder than mild steel, so do not attempt to cut, weld, or re-heat it, which destroys the heat treat and the rating with it.

Yes. Metallics lists field application for this bolt as the electrical, plumbing, heating, and air conditioning industries, which covers equipment anchorage, hanger and support steel, and machine mounting. The Grade 8 rating is heavier than most strut and hanger work requires, so it is the choice when the connection is carrying real load or vibration rather than for general trim work.