Metallics JLWI8 Washers 3/8 Int Tooth Lock St-zn (Jar 100)

The JLWI8 is a 3/8 inch internal tooth lock washer, so it goes over a 3/8-16 bolt or machine screw shank. Confirm your fastener is 3/8 and not 5/16 before you order, since a tooth washer that is one size up will spin on the shank and won't bite.

Internal tooth, like the JLWI8, puts the teeth on the inside diameter against the bolt shank, so the outer edge stays smooth and the washer stays hidden under the bolt head. That is what you want on finished surfaces, panel covers, and anywhere you don't want visible scoring. External tooth washers grip a wider circle and hold better on soft or oversized holes, but they mar the surface and show at the edge of the head.

The washers are steel with a zinc finish, which handles normal indoor and protected outdoor conditions but is not a stainless substitute. For wet locations, washdown areas, coastal exposure, or chemical service, specify stainless rather than zinc-plated steel.

On a 3/8 bolt, yes, both are drop-in at the same nominal size, but they work differently. A tooth washer like the JLWI8 spreads bite across many teeth and sits flatter, which suits sheet metal and thinner flanges. A split ring digs two points and is the usual choice on heavier structural joints. If the original joint spec calls out a split ring, match it rather than swap.

Each jar holds 100 of the 3/8 internal tooth lock washers, and the packed jar weighs 0.23 lbs. The jar form is handy on a van or a cart because it reseals, which a poly bag of loose washers does not.

Metallics lists the application as electrical, plumbing, heating and air conditioning work. In practice that means bolted strut and hanger connections, panel and enclosure hardware, equipment mounting feet, and anywhere a 3/8 bolted joint sees vibration and you need the fastener to stay put without a thread locker.

The jar measures 3 x 3 x 2.15 inches as listed, so it drops into most small parts bins and shelf trays without decanting. Useful if you are standardizing a service van or a shop wall on jarred fastener sizes.