Wood Nails by Size

Nails for wood by size

In Brazil, common nails carry a two-number label written as side × diameter. Those numbers point back to the wire gauge and a length code. Take 17 × 27: it works out to about 4 mm of gauge and 51 mm of length, and it happens to be one of the sizes you reach for most often in framing and everyday carpentry. The dimensional series itself is set by ABNT NBR 6627.

To pick a length, a handy starting point is L = 2.5 to 3 × t, with t being the thickness of the top board. The nail has to go all the way through the upper piece and then sink at least two thirds of its length into whatever it's biting into. The head shape matters as well. Use flat-head nails for structural joints, switch to oval-head (finishing) nails where you'd rather the head stay out of sight, and save headless nails for trim and moldings. Anywhere outdoors or damp, go with galvanized steel instead of plain bright wire so you don't end up with rust stains and nails that work loose.

Applications

Framing out structures like rafters, joists and studs; nailing down decking and shiplap; putting together pallets and crates; fixing wooden cleats and battens; fastening plywood subfloors; and trimming out moldings with bradnails. When you match the nail to the board thickness, the wood splits less and the joint resists pull-out better.

FAQ

What does 17×27 mean? The first number is the wire gauge (BWG ~17, around 4 mm across); the second is the length code (~27 lines, which comes out to about 51 mm long).

How do I avoid splitting hardwood? Drill a pilot hole at roughly 70 % of the nail’s diameter first, tap the tip flat with a hammer so it crushes the fibers rather than wedging them apart, and stagger the nails along the grain rather than lining them up.

Should I always use galvanized nails? Outdoors, in bathrooms, in kitchens, anywhere that sees moisture, yes. For dry interior framing, plain bright nails cost less and do the job just fine.