Black Zinc Plated Nuts | McMaster-Carr

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29 Products

Locknuts with External-Tooth Lock Washer

To save on assembly time, these locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand. Once the nut is against your material surface, tighten it down with a wrench or socket to get the teeth to bite. Although these nuts install more quickly than nylon-insert locknuts, they don't hold up as well against vibration and can mar your material. As long as the washer stays intact, you can reuse them. Also known as Keps and K-lock nuts.

Medium-Strength Steel

These Grade 5 or Class 8 nuts are your go-to for fastening most machinery and equipment. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.

	Wd., mm	Ht., mm	Fastener Strength Grade/Class	Washer OD, mm	Pkg. Qty.		Pkg.
Black-Zinc-Plated Steel



	M3 × 0.5 mm	5.5	3	ISO Class 8	7.1	100	000000000	000000


	M4 × 0.7 mm	7	4.1	ISO Class 8	8.5	100	000000000	00000
	M5 × 0.8 mm	8	5.2	ISO Class 8	9.5	100	000000000	00000
	M6 × 1 mm	10	6.2	ISO Class 8	12	50	000000000	00000
	M8 × 1.25 mm	13	8.5	ISO Class 8	15.5	25	000000000	00000
	M10 × 1.5 mm	17	9.7	ISO Class 8	20.1	10	000000000	00000

Low-Strength Steel

Rated Grade 2, Class 6, or lower, these locknuts are about half as strong as medium-strength steel nuts. Use them with screws that have a similar strength rating to avoid stripping threads during installation.

Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.

	Wd.	Ht.	Washer OD	Pkg. Qty.		Pkg.
Black-Zinc-Plated Steel



	4-40	1/4"	1/8"	0.281"	100	000000000	00000


	6-32	5/16"	9/64"	0.344"	100	000000000	0000
	8-32	11/32"	5/32"	0.375"	100	000000000	0000
	10-24	3/8"	5/32"	0.406"	100	000000000	0000
	10-32	3/8"	5/32"	0.406"	100	000000000	0000
	1/4"-20	7/16"	7/32"	0.5"	100	000000000	00000

Thin-Profile Nylon-Insert Locknuts

About half the height of standard-profile locknuts, these fit in spaces with low clearance. You can also use them as jam nuts by threading them against a hex nut to hold it in place. The nylon insert grips the screw to prevent loosening from moderate vibration without damaging threads. However, the insert may become brittle if exposed to high temperatures. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Low-Strength Steel

Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.

	Wd.	Ht.	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Black-Zinc-Plated Steel



	6-32	5/16"	1/8"	220	25	000000000	00000


	8-32	11/32"	11/64"	220	25	000000000	0000
	10-24	3/8"	11/64"	220	25	000000000	0000
	10-32	3/8"	11/64"	220	25	000000000	0000
	12-24	7/16"	13/64"	220	25	000000000	0000
	1/4"-20	7/16"	13/64"	220	25	000000000	0000
	5/16"-18	1/2"	1/4"	220	10	000000000	0000
	3/8"-16	9/16"	17/64"	220	10	000000000	0000

Low-Strength Steel Square Nuts

Large flat sides make these nuts easy to grip with a wrench and keep them from rotating in channels and square holes. About half the strength of medium-strength steel square nuts, use them in light duty fastening applications, such as securing access panels.

Black-Zinc-Plated Steel—Black-zinc-plated steel square nuts resist corrosion in wet environments and have a black finish that blends in with dark surfaces.

	Wd.	Ht.	Specs. Met	Pkg. Qty.		Pkg.
Black-Zinc-Plated Steel



	1/4"-20	7/16"	3/16"	—	100	000000000	000000


	5/16"-18	9/16"	7/32"	—	50	000000000	00000
	3/8"-16	5/8"	1/4"	—	50	000000000	00000


	Black-Zinc-Plated Steel—ISO Class 5



			M4 × 0.7 mm	7 mm	3 mm	DIN 557	25	000000000	0000


			M5 × 0.8 mm	8 mm	4 mm	DIN 557	25	000000000	0000
			M6 × 1 mm	10 mm	5 mm	DIN 557	25	000000000	0000
			M8 × 1.25 mm	13 mm	6.5 mm	DIN 557	10	000000000	0000
			M10 × 1.5 mm	17 mm	8 mm	DIN 557	10	000000000	00000
			M16 × 2 mm	24 mm	13 mm	DIN 557	1	000000000	0000