Metallics BLS43M Bolts 5/16 X 1-3/4 Hx Lag Blt St-zn (Box 1000)

The BLS43M measures 0.298 to 0.324 inch across the thread outside diameter, so it is a nominal 5/16 lag screw. Head width runs 0.484 to 0.500 inch, which is a 1/2 inch wrench or socket. For the pilot, drill to roughly the shank diameter of the unthreaded body in softwood and slightly larger in hardwood, and bore the top member to full 5/16 clearance so the threads pull the joint tight instead of jacking it apart.

No. The BLS43M is plain steel with a zinc finish and Metallics states it is for use in wood in non-corrosive environments. Zinc plating is an indoor and dry-location coating, so for exterior framing, treated lumber, or anything near salt air you want hot dip galvanized or stainless lags instead.

No. The BLS43M is not Buy American compliant and is not ARRA compliant, and country of origin is listed as multiple. If your spec carries a domestic sourcing clause, this is not the fastener to submit.

That is the normal use for it. The BLS43M is a full-bodied hex lag with spaced threads and a gimlet point, 9 threads per inch, rated at a 60,000 psi minimum tensile strength with hardness in the Rockwell B70 to B100 range. For anchoring strut straps or hanger brackets into studs or blocking, the controlling limit is usually the wood's withdrawal capacity and the thread depth you get into solid lumber, not the bolt itself.

Yes, the BLS43M is sold as a box of 1000 and the order minimum is 1000 pieces. Metallics notes other sizes and quantities are available by request, so if you need a different length or diameter in the BLS series it can be quoted rather than bought in this pack.

A lag like the BLS43M threads directly into wood with its gimlet point and spaced threads, so you only need access to one face, which is why it is the standard choice for strut, brackets, and hangers on studs, joists, and blocking. A through-bolt with nut and washer needs access to both sides but gives you a mechanically clamped joint that does not rely on thread grip in the wood fibre. At 1-3/4 inch overall, this lag is sized for thin-member attachment rather than heavy timber connections, where longer lags are used.

No washers are included with the BLS43M; it is a box of 1000 bare hex lag bolts. Any flat washer sized for a 5/16 fastener works under the head, and a washer is worth using whenever you are pulling down sheet metal strap or a soft wood face.