Metallics JCB43 Bolts 5/16-18 X 2-1/4 Carriage Blt S (Jar 100)

The JCB43 carriage bolt measures 0.298 to 0.324 inch across the shank (outside diameter), so a 5/16 inch bore is the matching hole. The square shoulder under the head needs to bite into the material to keep the bolt from spinning, so drill the hole to size rather than oversizing it, and pull the head down tight on a wood or soft substrate.

Steel with a zinc finish, not stainless. Zinc plating handles dry interior and protected work, but for sustained exposure to weather, treated lumber, or a wash-down area, specify a stainless carriage bolt instead. The plated version will corrode where the galvanic contact with ACQ-treated wood or standing moisture is constant.

The JCB43 carries a 60,000 psi minimum tensile strength and 36,000 psi minimum yield, with hardness in the Rockwell B70 to B100 range. That is low-carbon commercial bolt territory, suitable for general framing, strut, channel, and equipment mounting. If a drawing calls out a high-strength structural bolt for a load-bearing steel connection, this is not that fastener.

Both are flagged compliant on the JCB43, which matters on federally funded government, education, and municipal work where domestic-preference language is in the contract. Country of origin is listed as multiple, so if your specification requires a single named country of manufacture, confirm that separately with the submittal.

It is a 5/16-18 bolt, 18 threads per inch, which is the standard coarse (UNC) pitch for 5/16 inch. Any 5/16-18 hex nut will thread on; a flat washer under the nut is normal practice since the mushroom head side gets no washer.

The head is a mushroom (round dome) type measuring 0.688 to 0.719 inch across with a head height of 0.156 to 0.176 inch, so it sits proud of the surface as a low, smooth dome rather than flush. That low profile and the absence of any driver slot are the reason carriage bolts get used where a head is exposed to traffic or where you do not want it backed out from the finished side. If you need a flush, countersunk head, use a flat head machine or socket bolt instead.

Dimensions follow ASME B18.5-1990, the round head bolt standard. That is the citation to put on a submittal when an engineer asks what the head geometry and shoulder conform to, and it is why the head width and square shoulder interchange with any other B18.5 carriage bolt of the same 5/16-18 size.

They ship 100 to a jar, and 100 count is the order minimum. The jar packaging is what you want on a service truck or a shop bin since it reseals and does not spill like a bag. Jar weight is 2422 g.

Yes. The JCB43 is one size out of the Metallics CB and JCB carriage bolt series, and other sizes and quantities are available by request. If you are standardizing a maintenance shop, it is worth pinning down the two or three lengths your assemblies actually use rather than stocking one and shimming around it.