Lock Washer Nuts | McMaster-Carr

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82 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

Image of Product. Front orientation. ZoomedIn view. Locknuts. Locknuts with External-Tooth Lock Washer.

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.

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

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

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


	M3 × 0.5 mm	5.5 mm	3.3 mm	ISO Class 8	7.1 mm	100	000000000	000000
	M4 × 0.7 mm	7 mm	4.1 mm	ISO Class 8	8.5 mm	100	000000000	00000
	M5 × 0.8 mm	8 mm	5.2 mm	ISO Class 8	9.5 mm	100	000000000	00000
	M6 × 1 mm	10 mm	6.2 mm	ISO Class 8	12 mm	100	000000000	00000
	M8 × 1.25 mm	13 mm	8.5 mm	ISO Class 8	15.5 mm	25	000000000	0000
	M10 × 1.5 mm	17 mm	9.7 mm	ISO Class 8	20.1 mm	10	000000000	00000

	Black Zinc-Plated Steel


			M3 × 0.5 mm	5.5 mm	3 mm	ISO Class 8	7.1 mm	100	000000000	00000
			M4 × 0.7 mm	7 mm	4.1 mm	ISO Class 8	8.5 mm	100	000000000	00000
			M5 × 0.8 mm	8 mm	5.2 mm	ISO Class 8	9.5 mm	100	000000000	00000
			M6 × 1 mm	10 mm	6.2 mm	ISO Class 8	12 mm	50	000000000	00000
			M8 × 1.25 mm	13 mm	8.5 mm	ISO Class 8	15.5 mm	25	000000000	00000
			M10 × 1.5 mm	17 mm	9.7 mm	ISO Class 8	20.1 mm	10	000000000	00000

Low-Strength Steel

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

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

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.
Zinc-Plated Steel


	4-40	1/4"	7/64"	0.281"	100	000000000	00000
	5-40	5/16"	9/64"	0.344"	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
	12-24	7/16"	3/16"	0.5"	50	000000000	00000
	1/4"-20	7/16"	15/64"	0.5"	100	000000000	0000
	1/4"-28	7/16"	15/64"	0.5"	100	000000000	0000
	5/16"-18	1/2"	21/64"	0.578"	100	000000000	00000
	5/16"-24	1/2"	5/16"	0.592"	50	000000000	00000
	3/8"-16	9/16"	25/64"	0.656"	100	000000000	00000
	3/8"-24	9/16"	25/64"	0.656"	100	000000000	00000
	1/2"-13	3/4"	31/64"	0.891"	10	000000000	00000

	Black Zinc-Plated Steel


			4-40	1/4"	1/8"	0.281"	100	000000000	0000
			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	00000
			10-32	3/8"	5/32"	0.406"	100	000000000	00000
			1/4"-20	7/16"	7/32"	0.5"	100	000000000	00000

Corrosion-Resistant Stainless Steel

18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.

Black-Oxide 18-8 Stainless Steel—Typically chosen for their appearance, these nuts have a dark, matte coating to create a finished look. They resist rust in wet and outdoor environments, but won't hold up to the harsh chemicals that 316 stainless steel can.

	Wd.	Ht.	Washer OD	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	4-40	1/4"	1/8"	0.281"	100	000000000	00000
	4-48	1/4"	1/8"	0.281"	100	000000000	00000
	6-32	5/16"	9/64"	0.344"	100	000000000	0000
	8-32	11/32"	11/64"	0.375"	100	000000000	00000
	10-24	3/8"	11/64"	0.406"	100	000000000	00000
	10-32	3/8"	11/64"	0.406"	100	000000000	00000
	12-24	7/16"	11/64"	0.5"	50	000000000	00000
	1/4"-20	7/16"	15/64"	0.5"	50	000000000	00000
	1/4"-28	7/16"	15/64"	0.5"	50	000000000	00000
	5/16"-18	1/2"	21/64"	0.578"	25	000000000	0000
	5/16"-24	1/2"	21/64"	0.578"	25	000000000	00000
	3/8"-16	9/16"	25/64"	0.656"	25	000000000	00000
	3/8"-24	9/16"	25/64"	0.656"	10	000000000	0000
	1/2"-13	3/4"	7/16"	0.871"	10	000000000	0000
	M3 × 0.5 mm	5.5 mm	3.3 mm	6.5 mm	50	000000000	00000
	M4 × 0.7 mm	7 mm	4.1 mm	8.2 mm	50	000000000	00000
	M5 × 0.8 mm	8 mm	5.2 mm	9.5 mm	25	000000000	0000
	M6 × 1 mm	10 mm	6.2 mm	11.5 mm	25	000000000	0000
	M8 × 1.25 mm	13 mm	8.5 mm	15.1 mm	5	000000000	0000
	M10 × 1.5 mm	17 mm	9.7 mm	19.2 mm	5	000000000	00000

	Black-Oxide 18-8 Stainless Steel


			M3 × 0.5 mm	5.5 mm	3.3 mm	6.5 mm	25	000000000	0000
			M4 × 0.7 mm	7 mm	4.1 mm	8.2 mm	25	000000000	00000
			M5 × 0.8 mm	8 mm	5.2 mm	9.5 mm	25	000000000	00000
			M6 × 1 mm	10 mm	6.2 mm	11.5 mm	25	000000000	00000

Narrow-Profile Locknuts with External-Tooth Lock Washer

Since they're about 20% narrower, these locknuts fit in tight spaces where standard-profile nuts won't fit. They combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. 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.

Low-Strength Steel

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

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


	6-32	1/4"	1/8"	0.281"	100	000000000	000000
	8-32	5/16"	9/64"	0.344"	100	000000000	00000

Corrosion-Resistant Stainless Steel

18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.

	Wd.	Ht.	Washer OD	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	6-32	1/4"	3/32"	0.344"	100	000000000	000000

Locknuts with Spring-Lock Washer

The curved, spring-like washer grips surfaces more tightly than tooth-lock washers for better vibration resistance. These locknuts also install just as quickly since you can twist them into place by hand. Once the nut is against your material, tighten it down with a wrench or socket. The washer's smooth edges won't mar the surface like teeth can. As long as the washer stays intact, you can reuse these locknuts.

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.

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

Black-Oxide Steel—Typically chosen for their appearance, these nuts have a dark, matte coating to create a finished look. They offer minimal corrosion resistance, so they're best for dry environments.

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


	M3 × 0.5 mm	5.5 mm	3.8 mm	ISO Class 8	8 mm	50	000000000	000000
	M4 × 0.7 mm	7 mm	4.2 mm	ISO Class 8	10 mm	100	000000000	00000
	M5 × 0.8 mm	8 mm	5.3 mm	ISO Class 8	12 mm	100	000000000	00000
	M6 × 1 mm	10 mm	6.6 mm	ISO Class 8	14 mm	50	000000000	0000
	M8 × 1.25 mm	13 mm	8.8 mm	ISO Class 8	18 mm	50	000000000	00000
	M10 × 1.5 mm	17 mm	10.7 mm	ISO Class 8	22 mm	10	000000000	00000
	M12 × 1.75 mm	19 mm	13.8 mm	ISO Class 8	25.5 mm	25	000000000	00000

	Black-Oxide Steel


			M3 × 0.5 mm	5.5 mm	3.5 mm	ISO Class 8	10 mm	50	000000000	00000
			M4 × 0.7 mm	7 mm	4.2 mm	ISO Class 8	10 mm	50	000000000	00000
			M5 × 0.8 mm	8 mm	5.3 mm	ISO Class 8	12 mm	50	000000000	00000
			M6 × 1 mm	10 mm	6.6 mm	ISO Class 8	14 mm	25	000000000	0000

Low-Strength Steel

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

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


	4-40	1/4"	9/64"	0.328"	25	000000000	000000
	6-32	5/16"	9/64"	0.328"	25	000000000	00000
	8-32	11/32"	3/16"	0.375"	50	000000000	00000
	10-32	3/8"	3/16"	0.406"	25	000000000	00000
	1/4"-20	7/16"	3/16"	0.5"	10	000000000	00000

	Black-Oxide Steel


			4-40	1/4"	9/64"	0.328"	50	000000000	00000
			6-32	5/16"	9/64"	0.328"	25	000000000	00000
			8-32	11/32"	3/16"	0.375"	10	000000000	00000
			10-32	3/8"	3/16"	0.406"	10	000000000	0000
			1/4"-20	7/16"	3/16"	0.5"	10	000000000	00000

Assortments of Locknuts with External-Tooth Lock Washer

With a range of sizes on hand, you can use these assortments to fasten a variety of parts. These locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. 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.

Zinc-Plated Steel—A step up from plain steel, the zinc plating withstands occasional exposure to moisture.

18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.

	Locknuts Included	Container Type		Each
Zinc-Plated Steel


	600	4-40 (100 Pieces) 6-32 (100 Pieces) 8-32 (100 Pieces) 10-24 (100 Pieces) 10-32 (100 Pieces) 1/4"-20 (100 Pieces)	Plastic Box	000000000	000000

	18-8 Stainless Steel


			600	4-40 (100 Pieces) 6-32 (100 Pieces) 8-32 (100 Pieces) 10-24 (100 Pieces) 10-32 (100 Pieces) 1/4"-20 (100 Pieces)	Plastic Box	000000000	00000