Flex-Top Nuts | McMaster-Carr

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187 Products

Flex-Top Locknuts for Heavy Vibration

The top section of these nuts expands to grip the screw on all sides for a stronger hold than both nylon-insert and distorted-thread locknuts. They’re often used in equipment with constant, vigorous vibration, such as engines. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Steel

These locknuts have equivalent strength to Grade 8 and Class 10 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

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.

Cadmium-Plated Steel—These locknuts have good lubricity to thread on smoothly and ease installation. The plating also creates a barrier against rust that's comparable to zinc yellow-chromate plating.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Black-Oxide Steel


	1/4"-20	7/16"	19/64"	5	000000000	00000
	1/4"-28	7/16"	5/16"	5	000000000	0000
	5/16"-18	1/2"	23/64"	5	000000000	0000
	5/16"-24	1/2"	23/64"	5	000000000	0000
	3/8"-16	9/16"	15/32"	5	000000000	0000
	3/8"-24	9/16"	15/32"	5	000000000	0000
	7/16"-14	5/8"	15/32"	1	000000000	0000
	1/2"-13	3/4"	39/64"	1	000000000	0000
	1/2"-20	3/4"	39/64"	1	000000000	0000
	5/8"-11	15/16"	49/64"	1	000000000	0000
	5/8"-18	15/16"	49/64"	1	000000000	0000
	3/4"-10	1 1/16"	57/64"	1	000000000	00000
	3/4"-16	1 1/16"	57/64"	1	000000000	0000
	M6 × 1 mm	10 mm	7.8 mm	1	000000000	0000
	M8 × 1.25 mm	13 mm	10.4 mm	1	000000000	0000
	M10 × 1.5 mm	17 mm	13 mm	1	000000000	0000
	M12 × 1.75 mm	19 mm	15.6 mm	1	000000000	00000

	Cadmium-Plated Steel


			4-40	1/4"	5/32"	10	000000000	00000
			6-32	5/16"	3/16"	25	000000000	00000
			8-32	11/32"	1/4"	25	000000000	00000
			10-24	3/8"	1/4"	25	000000000	00000
			10-32	3/8"	1/4"	25	000000000	00000
			1/4"-20	7/16"	19/64"	25	000000000	00000
			1/4"-28	7/16"	5/16"	25	000000000	00000
			5/16"-18	1/2"	23/64"	10	000000000	0000
			5/16"-24	1/2"	23/64"	10	000000000	0000
			3/8"-16	9/16"	15/32"	10	000000000	00000
			3/8"-24	9/16"	15/32"	10	000000000	00000
			7/16"-14	5/8"	15/32"	5	000000000	00000
			7/16"-20	5/8"	15/32"	1	000000000	0000
			1/2"-13	3/4"	39/64"	5	000000000	00000
			1/2"-20	3/4"	39/64"	5	000000000	00000
			9/16"-18	7/8"	31/64"	1	000000000	00000
			5/8"-11	15/16"	49/64"	1	000000000	0000
			5/8"-18	15/16"	49/64"	1	000000000	0000
			3/4"-10	1 1/16"	57/64"	1	000000000	0000
			3/4"-16	1 1/16"	57/64"	1	000000000	0000
			7/8"-9	1 1/4"	1 1/64"	1	000000000	00000
			7/8"-14	1 1/4"	1 1/64"	1	000000000	00000
			1"-8	1 7/16"	1 9/64"	1	000000000	00000
			1"-14	1 7/16"	1 9/64"	1	000000000	00000
			M6 × 1 mm	10 mm	7.8 mm	5	000000000	00000
			M8 × 1.25 mm	13 mm	10.4 mm	1	000000000	0000
			M10 × 1.5 mm	17 mm	13 mm	1	000000000	00000
			M12 × 1.75 mm	19 mm	15.6 mm	1	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.

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


	2-56	1/4"	5/32"	5	000000000	000000
	6-32	5/16"	3/16"	5	000000000	0000
	8-32	11/32"	1/4"	5	000000000	0000
	10-24	3/8"	1/4"	5	000000000	0000
	10-32	3/8"	1/4"	10	000000000	00000
	1/4"-20	7/16"	19/64"	5	000000000	00000
	1/4"-28	7/16"	19/64"	5	000000000	0000
	5/16"-18	1/2"	23/64"	1	000000000	0000
	5/16"-24	1/2"	23/64"	1	000000000	0000
	3/8"-16	9/16"	15/32"	1	000000000	0000
	3/8"-24	9/16"	15/32"	1	000000000	0000
	7/16"-20	5/8"	15/32"	1	000000000	00000
	1/2"-13	3/4"	39/64"	1	000000000	0000
	1/2"-20	3/4"	39/64"	1	000000000	0000
	M3 × 0.5 mm	5.5 mm	4.5 mm	1	000000000	0000
	M4 × 0.7 mm	7 mm	6 mm	1	000000000	0000
	M5 × 0.8 mm	8 mm	7.5 mm	1	000000000	0000
	M6 × 1 mm	10 mm	7.8 mm	1	000000000	0000
	M8 × 1.25 mm	13 mm	10.4 mm	1	000000000	0000
	M10 × 1.5 mm	17 mm	13 mm	1	000000000	00000
	M12 × 1.75 mm	19 mm	15.6 mm	1	000000000	00000
	M14 × 2 mm	22 mm	18.2 mm	1	000000000	00000
	M16 × 2 mm	24 mm	20.8 mm	1	000000000	00000
	M18 × 2.5 mm	27 mm	23.4 mm	1	000000000	00000
	M20 × 2.5 mm	30 mm	26 mm	1	000000000	00000
	M22 × 2.5 mm	32 mm	28.6 mm	1	000000000	00000
	M24 × 3 mm	36 mm	31.2 mm	1	000000000	00000

	Black-Oxide 18-8 Stainless Steel


			8-32	11/32"	1/4"	5	000000000	0000
			10-24	3/8"	1/4"	5	000000000	0000
			10-32	3/8"	1/4"	5	000000000	0000
			1/4"-20	7/16"	19/64"	5	000000000	00000
			5/16"-18	1/2"	23/64"	1	000000000	0000
			3/8"-16	9/16"	15/32"	1	000000000	0000
			1/2"-13	3/4"	39/64"	1	000000000	0000
			1/2"-20	3/4"	39/64"	1	000000000	0000

			316 Stainless Steel


					M3 × 0.5 mm	5.5 mm	4.5 mm	1	000000000	0000
					M4 × 0.7 mm	7 mm	6 mm	1	000000000	0000
					M5 × 0.8 mm	8 mm	7.5 mm	1	000000000	0000
					M6 × 1 mm	10 mm	7.8 mm	1	000000000	0000
					M8 × 1.25 mm	13 mm	10.4 mm	1	000000000	0000
					M10 × 1.5 mm	17 mm	13 mm	1	000000000	00000
					M12 × 1.75 mm	19 mm	15.6 mm	1	000000000	00000
					M20 × 2.5 mm	30 mm	26 mm	1	000000000	00000

Thin-Profile Flex-Top Locknuts for Heavy Vibration

About two-thirds the height of standard flex-top nuts, 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 top section expands to grip the screw on all sides for a stronger hold than both nylon-insert and distorted-thread locknuts. As a result, they're suitable for use in equipment with constant, vigorous vibration, such as engines. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Steel

These locknuts have equivalent strength to Grade 8 and Class 10 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

Steel—These locknuts are best for dry environments since moisture will cause them to rust.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Cadmium-Plated Steel


	6-32	5/16"	9/64"	25	000000000	000000
	8-32	11/32"	3/16"	25	000000000	00000
	10-24	3/8"	3/16"	25	000000000	00000
	10-32	3/8"	3/16"	25	000000000	00000
	1/4"-20	7/16"	7/32"	25	000000000	00000
	1/4"-28	7/16"	7/32"	25	000000000	00000
	5/16"-18	1/2"	17/64"	10	000000000	0000
	5/16"-24	1/2"	17/64"	10	000000000	00000
	3/8"-16	9/16"	9/32"	10	000000000	00000
	3/8"-24	9/16"	9/32"	10	000000000	00000
	7/16"-20	5/8"	21/64"	5	000000000	00000
	1/2"-13	3/4"	21/64"	5	000000000	00000
	1/2"-20	3/4"	21/64"	5	000000000	00000
	5/8"-11	15/16"	13/32"	1	000000000	0000
	5/8"-18	15/16"	13/32"	1	000000000	0000
	3/4"-10	1 1/16"	27/64"	1	000000000	0000
	3/4"-16	1 1/16"	27/64"	1	000000000	0000
	7/8"-9	1 1/4"	31/64"	1	000000000	00000
	1"-8	1 7/16"	37/64"	1	000000000	00000
	1"-14	1 7/16"	37/64"	1	000000000	00000
	1 1/8"-12	1 5/8"	41/64"	1	000000000	00000
	1 1/4"-12	1 13/16"	49/64"	1	000000000	00000
	1 1/2"-12	2 3/16"	57/64"	1	000000000	00000

	Steel


			6-32	5/16"	9/64"	10	000000000	0000
			8-32	11/32"	3/16"	10	000000000	0000
			10-24	3/8"	3/16"	10	000000000	0000
			10-32	3/8"	3/16"	10	000000000	0000
			1/4"-20	7/16"	7/32"	10	000000000	0000
			1/4"-28	7/16"	7/32"	10	000000000	0000
			5/16"-18	1/2"	17/64"	5	000000000	0000
			5/16"-24	1/2"	17/64"	5	000000000	0000
			3/8"-16	9/16"	9/32"	5	000000000	0000
			3/8"-24	9/16"	9/32"	5	000000000	0000
			1/2"-13	3/4"	21/64"	1	000000000	0000
			1/2"-20	3/4"	21/64"	1	000000000	0000
			5/8"-11	15/16"	13/32"	1	000000000	0000
			5/8"-18	15/16"	13/32"	1	000000000	0000
			3/4"-10	1 1/16"	27/64"	1	000000000	0000
			3/4"-16	1 1/16"	27/64"	1	000000000	0000
			1"-14	1 7/16"	37/64"	1	000000000	0000
			1 1/8"-12	1 5/8"	41/64"	1	000000000	00000
			1 1/4"-12	1 13/16"	49/64"	1	000000000	00000
			1 3/8"-12	1 15/16"	53/64"	1	000000000	00000
			1 1/2"-12	2 3/16"	57/64"	1	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.	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	6-32	5/16"	9/64"	10	000000000	000000
	8-32	11/32"	3/16"	5	000000000	00000
	10-24	3/8"	3/16"	5	000000000	00000
	10-32	3/8"	3/16"	10	000000000	00000
	1/4"-20	7/16"	7/32"	5	000000000	00000
	1/4"-28	7/16"	7/32"	5	000000000	00000
	5/16"-18	1/2"	17/64"	1	000000000	0000
	5/16"-24	1/2"	17/64"	1	000000000	0000
	3/8"-16	9/16"	9/32"	1	000000000	0000
	3/8"-24	9/16"	9/32"	1	000000000	0000
	1/2"-13	3/4"	21/64"	1	000000000	0000
	1/2"-20	3/4"	21/64"	1	000000000	00000
	5/8"-18	15/16"	13/32"	1	000000000	00000
	3/4"-16	1 1/16"	27/64"	1	000000000	00000
	7/8"-14	1 1/4"	31/64"	1	000000000	000000

Heavy-Profile Flex-Top Locknuts for Heavy Vibration

About 10% wider and taller than standard flex-top nuts, these handle heavier loads by distributing them over a larger area. The top section expands to grip the screw on all sides for a stronger hold than both nylon-insert and distorted-thread locknuts. As a result, they're suitable for use in equipment with constant, vigorous vibration, such as engines. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Steel

These locknuts have equivalent strength to Grade 8 and Class 10 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Cadmium-Plated Steel


	1/4"-20	1/2"	19/64"	10	000000000	000000
	5/16"-18	9/16"	21/64"	10	000000000	00000
	3/8"-16	5/8"	25/64"	10	000000000	00000
	1/2"-13	13/16"	1/2"	5	000000000	00000
	5/8"-11	1"	41/64"	1	000000000	0000
	3/4"-10	1 1/8"	49/64"	1	000000000	0000
	7/8"-9	1 5/16"	57/64"	1	000000000	00000
	1"-8	1 1/2"	1 1/64"	1	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.	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	1/4"-20	1/2"	19/64"	1	000000000	000000
	5/16"-18	9/16"	21/64"	1	000000000	00000
	3/8"-16	5/8"	25/64"	1	000000000	00000
	7/16"-14	3/4"	29/64"	1	000000000	00000
	1/2"-13	13/16"	1/2"	1	000000000	00000

Thin-Heavy-Profile Flex-Top Locknuts for Heavy Vibration

About two-thirds the height of standard flex-top nuts and 10% wider, these fit in spaces with low clearance and handle heavier loads by distributing them over a larger area. Because of the thin profile, you can also use them as jam nuts by threading them against a hex nut to hold it in place. The top section expands to grip the screw on all sides for a stronger hold than both nylon-insert and distorted-thread locknuts. As a result, they're suitable for use in equipment with constant, vigorous vibration, such as engines. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Steel

These locknuts have equivalent strength to Grade 8 and Class 10 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Cadmium-Plated Steel


	1/4"-20	1/2"	7/32"	25	000000000	000000
	5/16"-18	9/16"	17/64"	10	000000000	0000
	3/8"-16	5/8"	9/32"	10	000000000	00000
	7/16"-14	3/4"	21/64"	1	000000000	0000
	1/2"-13	13/16"	21/64"	5	000000000	00000
	5/8"-11	1"	13/32"	1	000000000	0000
	3/4"-10	1 1/8"	27/64"	1	000000000	00000
	7/8"-9	1 5/16"	31/64"	1	000000000	00000
	1"-8	1 1/2"	37/64"	1	000000000	00000

Mil. Spec. Flex-Top Locknuts for Heavy Vibration

These locknuts are manufactured and tested to strict U.S. military standards for material and construction. The top section expands to grip the screw on all sides for a stronger hold than both nylon-insert and distorted-thread locknuts. As a result, they're suitable for use in equipment with constant, vigorous vibration, such as engines. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Steel

These locknuts have equivalent strength to Grade 8 and Class 10 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

Cadmium Yellow-Chromate-Plated Steel—These locknuts have good lubricity to thread on smoothly and ease installation. The plating also creates a barrier against rust that's comparable to zinc yellow-chromate plating.

	Wd.	Ht.	Mil. Specs. Met	Pkg. Qty.		Pkg.
Cadmium Yellow-Chromate-Plated Steel


	4-40	1/4"	5/32"	MS21045-04	5	000000000	000000
	6-32	5/16"	3/16"	MS21045-06	5	000000000	0000
	8-32	11/32"	1/4"	MS21045-08	5	000000000	00000
	10-32	3/8"	1/4"	MS21045-3	5	000000000	0000
	1/4"-28	7/16"	5/16"	MS21045-4	5	000000000	00000
	5/16"-24	1/2"	23/64"	MS21045-5	5	000000000	00000
	3/8"-24	9/16"	15/32"	MS21045-6	5	000000000	00000
	7/16"-20	11/16"	15/32"	MS21045-7	1	000000000	00000
	1/2"-20	3/4"	39/64"	MS21045-8	1	000000000	00000
	9/16"-18	7/8"	11/16"	MS21045-9	1	000000000	00000
	5/8"-18	15/16"	49/64"	MS21045-10	1	000000000	00000
	3/4"-16	1 1/16"	57/64"	MS21045-12	1	000000000	00000

Corrosion-Resistant Stainless Steel

Silver-Plated 18-8 Stainless Steel—The choice for wet and outdoor environments, these locknuts won't rust. The silver plating adds lubricity to help them thread on smoothly during installation.

	Wd.	Ht.	Mil. Specs. Met	Specs. Met	Pkg. Qty.		Pkg.
Silver-Plated 18-8 Stainless Steel


	4-40	1/4"	9/64"	MS21046C04	NASM21046	1	000000000	000000
	6-32	5/16"	11/64"	MS21046C06	NASM21046	1	000000000	00000
	8-32	11/32"	15/64"	MS21046C08	NASM21046	1	000000000	0000
	10-32	3/8"	15/64"	MS21046C3	NASM21046	1	000000000	00000
	1/4"-28	7/16"	9/32"	MS21046C4	NASM21046	1	000000000	00000
	3/8"-24	9/16"	25/64"	MS21046C6	NASM21046	1	000000000	00000