Metallics JCB27G Bolts 3/8-16 x 3-1/2 Carriage Blt Ga (Jar 25)

The JCB27G is a galvanized steel carriage bolt, so the zinc coating gives it corrosion resistance for exterior framing, wet locations, and treated-lumber work where a plain steel bolt would rust out. The body is steel throughout.

Shank diameter on the JCB27G runs 0.360 to 0.388 inch, so a 3/8 inch (0.375) bore is the matching hole. Drill it clean and tight, because a carriage bolt relies on the square shoulder under the head biting into the wood to keep the bolt from spinning while you tighten the nut. Oversize the hole and the shoulder has nothing to grab.

Thread is 3/8-16, so it takes a standard 3/8-16 coarse hex nut. The jar is bolts only, so order nuts and washers separately. On wood, use a washer under the nut, not under the head, since the mushroom head is meant to seat flush against the surface.

The head is a mushroom type measuring 0.782 to 0.844 inch across and only 0.188 to 0.208 inch high, so it sits low and smooth with no wrench flats or sharp edges. That is why carriage bolts get used on handrails, playground structures, gates, and anywhere a protruding hex head would catch clothing or hands.

No. The JCB27G ships as a jar of 25 pieces, and 25 count is the order minimum. Other sizes and quantities in the CB and JCB carriage bolt series can be had by request.

Metallics lists the JCB27G as both Buy American compliant and ARRA compliant. Country of origin is recorded as multiple, so the sourcing varies by production run while the compliance flags hold.

Use a carriage bolt like the JCB27G when you can get to both sides of the connection and want a smooth, low-profile head on the show side. The square shoulder under the mushroom head locks into the wood so you tighten from the nut side only, with one wrench. If you can only reach one face, a lag screw is what you want. If the head is hidden and you need a wrench grip on both ends or a higher strength grade than 36,000 psi yield, go with a hex bolt.