Metallics JLWX7M Washers 5/16 Ext Tooth Lock St-zn (Jar 1000)

The JLWX7M is a 5/16 inch external tooth lock washer, so it suits 5/16 inch bolts and screws. The teeth sit on the outside diameter, which puts the bite under the bolt head or nut face at the outer edge rather than against the inside of the hole.

One jar holds 1,000 pieces of the 5/16 external tooth lock washer, packed in a jar rather than a box. Total packed weight is 0.96 lbs, and the jar measures 3 x 3.6 x 3 inches, so it stores easily on a van shelf or in a parts bin.

Steel with a zinc plating, which is the standard finish for interior electrical and general fastening work. For wet, exterior, or corrosive locations you want a stainless or hot dip galvanized washer instead, since zinc plating is a light coating.

Both resist loosening, but they work differently. The external tooth style, like the JLWX7M in 5/16, has serrated teeth around the outer rim that spread the locking bite over a wide circle, which helps on sheet metal, strut, and enclosure work where the bearing surface is thin. A split ring concentrates its force at one cut end and bites more aggressively into a thicker, solid surface. External tooth washers also scrape plating and paint, which is why electricians use them where a bonding path matters.

No. The JLWX7M is sized to the 5/16 inch imperial bolt, and while 8mm is close it is slightly larger, so an 8mm bolt will not pass cleanly through. Order a metric M8 external tooth washer for metric hardware.

The teeth on this style cut through paint and plating as the nut is drawn down, which is why external tooth lock washers are a common choice under ground lugs and bonding screws on painted enclosures and strut. It is a steel washer with zinc plate, not a listed bonding device on its own, so follow whatever the lug or enclosure manufacturer specifies for the connection itself.

The 5/16 external tooth lock washer is built to ANSI dimensional standards, so the inside and outside diameters interchange with other ANSI-spec 5/16 tooth washers already on a job. Country of origin is listed as multiple.