Metallics JBSC51658 5/16-18 x 5/8 in. Socket Button Head Hex Cap Screws - Alloy Steel Black - Each

Yes. The JBSC51658 is 5/16-18 UNC, 18 threads per inch, cut to ANSI/ASME B1.1, which is the standard coarse thread for 5/16 inch hardware. It mates with any 5/16-18 nut, strut channel nut, or tapped hole. It will not thread into a 5/16-24 fine-thread hole.

No. Metallics states these button head screws are not recommended for critical, high-strength applications. The low-profile head has less bearing area and less socket depth than a standard socket head cap screw, so for structural or high-torque work use a standard socket head cap screw or a hex cap screw in the proper grade. For general electrical, plumbing, and HVAC mounting, which is what these are intended for, they're fine.

No. The finish is black alloy steel and Metallics specifies the screws are supplied plain, meaning no zinc, no galvanizing, no protective plating. Alloy steel supplied plain will rust in wet or exterior conditions, so keep these to dry interior work and specify a zinc-plated or stainless 5/16-18 screw for anything damp, exterior, or corrosive.

No. These are not Buy American compliant and not ARRA compliant, with country of origin listed as multiple. If your contract carries a domestic-sourcing clause, this part will not satisfy it and you'll need a domestically produced 5/16-18 socket cap screw instead.

It's a hex (Allen) socket drive, not a slotted or Torx head, so you drive it with a hex key. Socket depth is 0.105 inch, which is what limits how much key engagement you get, so use a clean, fully seated key to avoid rounding out the socket. Head width runs 0.527 to 0.547 inch and head height 0.152 to 0.166 inch, so plan clearance around the head accordingly.

Minimum tensile strength is 7,300 lb and hardness is Rockwell C39-44, built to the ASME B18.3-2012 dimensional standard. Note Metallics' own test caveat: screws must be at least 3 diameters long to be subject to tensile testing, and at 5/8 inch on a 5/16 diameter this one sits right around that threshold, so treat the 7,300 lb figure as the series rating rather than a proof load for this length.

The button head is the low-profile choice. With head height of 0.152 to 0.166 inch it sits much flatter than a standard socket head cap screw, which matters when the screw head has to clear a panel, cover, or passing cable. The trade-off is strength: a standard socket head cap screw takes a deeper hex key and handles higher loads, and Metallics specifically says these button heads aren't for critical, high-strength work. Pick button head for clearance and appearance, standard socket head for load.

They ship in a jar of 100, which is the order minimum. Jar weight is listed at 1.55 lbs. Metallics offers other sizes and quantities in the BSC button head socket cap screw series by request.