Reversible Locknuts | McMaster-Carr

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Material

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Zinc Yellow-Chromate Plated

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Unified Standard Class 2B

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92 Products

Performance

High Strength

Withstand heavy loads and high stress without cracking

38 products

Corrosion Resistant

Won't rust in wet and outdoor environments

23 products

Thread Direction

Left Hand

Secure parts that rotate counterclockwise, such as the propeller on a mixer

6 products

Center-Lock Distorted-Thread Locknuts

Also known as reversible locknuts, these thread on from either side, so you don't have to worry about fastening them incorrectly and damaging your screw. The irregularly shaped threads in the middle grip the screw for a stronger hold than nylon-insert locknuts. Although the threads prevent the nut from backing out due to vibration, they also increase the effort to install and remove. To get these nuts off, you may need special tools, such as an impact wrench or propane torch. Nuts are not reusable.

High-Strength Steel

Rated Grade 8, Grade C, or Class 10, these locknuts are about 25% stronger than medium-strength steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

Zinc-Yellow-Chromate-Plated Steel—With a more durable finish than clear zinc plating, these nuts are suitable for most wet and outdoor environments. However, they won't hold up to the harsh chemicals that stainless steel can.

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.

Zinc-Flake-Coated Steel—The most durable zinc coating, this multilayer finish resists wear for long-term rust protection. However, similar to zinc-yellow-chromate plating, it won't hold up to harsh chemicals like stainless steel can.

	Wd.	Ht.	Fastener Strength Grade/Class	Pkg. Qty.		Pkg.
Zinc-Yellow-Chromate-Plated Steel



	1/4"-20	7/16"	7/32"	SAE Grade 8	50	000000000	000000


	1/4"-28	7/16"	7/32"	SAE Grade 8	50	000000000	00000
	5/16"-18	1/2"	17/64"	SAE Grade 8	50	000000000	00000
	5/16"-24	1/2"	17/64"	SAE Grade 8	50	000000000	00000
	3/8"-16	9/16"	21/64"	SAE Grade 8	25	000000000	0000
	3/8"-24	9/16"	21/64"	SAE Grade 8	25	000000000	00000
	7/16"-14	11/16"	3/8"	SAE Grade 8	10	000000000	0000
	7/16"-20	11/16"	3/8"	SAE Grade 8	10	000000000	0000
	1/2"-13	3/4"	7/16"	SAE Grade 8	10	000000000	0000
	1/2"-20	3/4"	7/16"	SAE Grade 8	10	000000000	00000
	9/16"-12	7/8"	31/64"	SAE Grade 8	10	000000000	00000


	5/8"-11	15/16"	35/64"	SAE Grade 8	5	000000000	0000
	5/8"-18	15/16"	35/64"	SAE Grade 8	5	000000000	0000
	3/4"-10	1 1/8"	41/64"	SAE Grade 8	5	000000000	0000
	3/4"-16	1 1/8"	41/64"	SAE Grade 8	5	000000000	00000
	7/8"-9	1 5/16"	3/4"	SAE Grade 8	5	000000000	00000
	1"-8	1 1/2"	55/64"	SAE Grade 8	1	000000000	0000
	1"-14	1 1/2"	55/64"	SAE Grade 8	1	000000000	00000


	Black-Oxide Steel



			1/4"-20	7/16"	7/32"	SAE Grade 8	10	000000000	0000


			5/16"-18	1/2"	17/64"	SAE Grade 8	10	000000000	0000
			3/8"-16	9/16"	21/64"	SAE Grade 8	10	000000000	0000
			1/2"-13	3/4"	7/16"	SAE Grade 8	5	000000000	00000
			5/8"-11	15/16"	35/64"	SAE Grade 8	1	000000000	0000
			7/8"-9	1 5/16"	3/4"	SAE Grade 8	1	000000000	00000
			1"-8	1 1/2"	55/64"	SAE Grade 8	1	000000000	00000
			1"-14	1 1/2"	55/64"	SAE Grade 8	1	000000000	00000


			Zinc-Flake-Coated Steel



					1/4"-20	7/16"	7/32"	SAE Grade 8	10	000000000	0000


					5/16"-18	1/2"	17/64"	SAE Grade 8	10	000000000	00000
					3/8"-16	9/16"	21/64"	SAE Grade 8	5	000000000	0000
					1/2"-13	3/4"	7/16"	SAE Grade 8	5	000000000	00000
					5/8"-11	15/16"	35/64"	SAE Grade 8	1	000000000	0000
					1"-8	1 1/2"	55/64"	SAE Grade 8	1	000000000	00000

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.

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



	M5 × 0.8 mm	8	4	ISO Class 8	10	000000000	000000


	M6 × 1 mm	10	5	ISO Class 8	10	000000000	00000
	M7 × 1 mm	11	5.5	ISO Class 8	5	000000000	0000
	M8 × 1 mm	13	6.5	ISO Class 8	10	000000000	00000
	M8 × 1.25 mm	13	6.5	ISO Class 8	10	000000000	00000
	M10 × 1 mm	17	8	ISO Class 8	5	000000000	0000
	M10 × 1.25 mm	17	8	ISO Class 8	5	000000000	0000
	M10 × 1.5 mm	17	8	ISO Class 8	10	000000000	00000
	M12 × 1.25 mm	19	10	ISO Class 8	5	000000000	00000
	M12 × 1.5 mm	19	10	ISO Class 8	5	000000000	00000
	M12 × 1.75 mm	19	10	ISO Class 8	5	000000000	0000


	M14 × 1.5 mm	22	11	ISO Class 8	5	000000000	00000
	M14 × 2 mm	22	11	ISO Class 8	5	000000000	00000
	M16 × 1.5 mm	24	13	ISO Class 8	5	000000000	00000
	M16 × 2 mm	24	13	ISO Class 8	5	000000000	00000
	M22 × 1.5 mm	32	18	ISO Class 8	1	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.

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

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



	1/4"-20	7/16"	7/32"	SAE Grade 2	100	000000000	00000


	1/4"-28	7/16"	7/32"	SAE Grade 2	100	000000000	00000
	5/16"-18	1/2"	17/64"	SAE Grade 2	100	000000000	0000
	5/16"-24	1/2"	17/64"	SAE Grade 2	100	000000000	0000
	3/8"-16	9/16"	21/64"	SAE Grade 2	100	000000000	00000
	3/8"-24	9/16"	21/64"	SAE Grade 2	100	000000000	00000
	7/16"-14	11/16"	3/8"	SAE Grade 2	50	000000000	00000
	7/16"-20	11/16"	3/8"	SAE Grade 2	50	000000000	00000
	1/2"-13	3/4"	7/16"	SAE Grade 2	50	000000000	00000
	1/2"-20	3/4"	7/16"	SAE Grade 2	50	000000000	00000
	5/8"-11	15/16"	35/64"	SAE Grade 2	25	000000000	00000


	5/8"-18	15/16"	35/64"	SAE Grade 2	25	000000000	00000
	3/4"-10	1 1/8"	41/64"	SAE Grade 2	10	000000000	00000
	3/4"-16	1 1/8"	41/64"	SAE Grade 2	10	000000000	00000
	1"-14	1 1/2"	55/64"	SAE Grade 2	5	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.

316 Stainless Steel—Our most corrosion-resistant nuts, these hold up in just about any environment. They won't degrade from exposure to weather, salt water, and most chemicals.

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



	1/4"-20	7/16"	7/32"	50	000000000	00000


	1/4"-28	7/16"	7/32"	50	000000000	00000
	5/16"-18	1/2"	17/64"	50	000000000	00000
	5/16"-24	1/2"	17/64"	25	000000000	0000
	3/8"-16	9/16"	21/64"	25	000000000	0000
	3/8"-24	9/16"	21/64"	25	000000000	0000
	7/16"-14	11/16"	3/8"	10	000000000	0000
	7/16"-20	11/16"	3/8"	10	000000000	0000
	1/2"-13	3/4"	7/16"	10	000000000	0000
	1/2"-20	3/4"	7/16"	10	000000000	0000
	5/8"-11	15/16"	35/64"	5	000000000	0000


	5/8"-18	15/16"	35/64"	5	000000000	00000
	3/4"-10	1 1/8"	41/64"	5	000000000	00000
	3/4"-16	1 1/8"	41/64"	1	000000000	0000
	7/8"-9	1 5/16"	3/4"	1	000000000	0000
	1"-8	1 1/2"	55/64"	1	000000000	0000
	1"-14	1 1/2"	55/64"	1	000000000	0000


	316 Stainless Steel



			1/4"-20	7/16"	7/32"	10	000000000	0000


			5/16"-18	1/2"	17/64"	10	000000000	0000
			3/8"-16	9/16"	21/64"	10	000000000	0000
			1/2"-13	3/4"	7/16"	5	000000000	0000
			5/8"-11	15/16"	35/64"	1	000000000	0000
			3/4"-10	1 1/8"	41/64"	1	000000000	0000

Left-Hand-Thread Center-Lock Distorted-Thread Locknuts

Secure parts that rotate counterclockwise, such as the propeller on a mixer. Also known as reversible locknuts, these thread on from either side, so you don't have to worry about fastening them incorrectly and damaging your screw. The irregularly shaped threads in the middle grip the screw for a stronger hold than nylon-insert locknuts. Although the threads prevent the nut from backing out due to vibration, they also increase the effort to install and remove. To get these nuts off, you may need special tools, such as an impact wrench or propane torch. Nuts are not reusable.

High-Strength Steel

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

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



	1/4"-20	7/16"	7/32"	SAE Grade 8	25	000000000	000000


	5/16"-18	1/2"	17/64"	SAE Grade 8	25	000000000	00000
	3/8"-16	9/16"	21/64"	SAE Grade 8	10	000000000	0000
	1/2"-13	3/4"	7/16"	SAE Grade 8	10	000000000	00000
	5/8"-11	15/16"	35/64"	SAE Grade 8	5	000000000	00000
	3/4"-10	1 1/8"	41/64"	SAE Grade 8	5	000000000	00000