Metallics JSBH3581 Bolts 1/2-20 x 3-1/2 HXBT SS (Jar 50)

Fine thread. The JSBH3581 is a 1/2-20 hex bolt, 20 threads per inch, which is the UNF fine pitch rather than the 1/2-13 UNC coarse pitch. It will only thread into a 1/2-20 nut or tapped hole; a coarse 1/2-13 nut will not run on it. Check the mating nut or tapped part before ordering, because the two pitches look nearly identical by eye.

18-8 austenitic stainless is what these bolts are made from, and it is intended for general atmospheric corrosion resistance, the kind of service you get in chemical and food processing equipment. That covers normal exterior and washdown duty. Aggressive chemical exposure or chloride-heavy environments can call for a more corrosion resistant alloy such as 316, so match the alloy to the chemistry rather than assuming 18-8 covers everything.

A 3/4 inch socket or wrench. The hex head measures 0.736 to 0.750 inch across the flats, so a standard 3/4 inch drive fits it. Useful to know before you get to a tight panel or strut run with the wrong roll of sockets.

Yes. The shank runs 0.4930 to 0.5000 inch outside diameter, so it drops into a standard 1/2 inch clearance hole (typically drilled 9/16 inch) without reaming. It is not a press fit part, so if the hole was drilled at exactly 1/2 inch you may need to open it slightly.

The JSBH3581 is rated at 100,000 to 150,000 psi minimum tensile and 65,000 psi minimum yield, with hardness in the Rockwell B95 to C32 range. That is in the general range of a medium-strength carbon bolt but 18-8 stainless is chosen for corrosion resistance, not for maximum strength. For a structural connection with a specified bolt grade on the drawing, use the graded carbon bolt the spec calls for; use this where the joint has to survive the environment.

They ship in a jar of 50 pieces, and 50 each is the order minimum, so the jar is the smallest unit. Metallics notes that other sizes and quantities are available by request if 50 of the 1/2-20 x 3-1/2 is not what the job needs.

Both flags are marked compliant on the JSBH3581, Buy American and ARRA, which is what a government, school, or healthcare procurement file usually needs on a fastener line item. Country of origin is listed as multiple, so if your contract requires a single named origin on the submittal, confirm the origin of the specific lot you receive.

No, these are 18-8. Both 18-8 and 316 stainless cap screws are austenitic alloys, so they behave similarly in handling and galling, but 316 adds molybdenum for better resistance to chlorides and harsher chemical exposure. If the application is coastal, in a chlorinated process, or a wastewater environment, specify 316 instead of this 18-8 bolt.