Self-Locking Acorn Nuts | McMaster-Carr

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79 Products

Performance

Corrosion Resistant

Won't rust in wet and outdoor environments

50 products

Locking Type

Threadlocker

A nylon patch on the threads resists loosening from mild vibration

26 products

Locking Type

Nylon Insert

A nylon insert prevents loosening from moderate vibration

21 products

Distorted Thread

Irregularly shaped threads grip better than a nylon insert

32 products

Cap Nuts with Threadlocker

These nuts not only conceal and protect protruding screw threads, they also resist loosening from mild vibration. They have a nylon patch bonded to their threads that grips screws for a tighter hold than standard cap nuts. They’re reusable a handful of times, but the patch’s holding power decreases with each use. Also known as acorn nuts, they have a smooth, rounded head that creates a finished look.

Stainless Steel

Image of Product. Front orientation. Contains Annotated, Border. Cap Nuts. Cap Nuts with Threadlocker.

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

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

	Thread Dp.	Wd.	Ht.	Specs. Met	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	10-24	3/16"	3/8"	13/32"	—	5	90421A110	000000


	10-32	3/16"	3/8"	13/32"	—	5	90421A120	00000
	12-24	7/32"	3/8"	13/32"	—	5	90421A130	00000
	1/4"-20	1/4"	7/16"	15/32"	—	5	90421A140	00000
	1/4"-28	1/4"	7/16"	15/32"	—	5	90421A150	00000
	5/16"-18	19/64"	1/2"	17/32"	—	5	90421A160	00000
	3/8"-16	3/8"	9/16"	5/8"	—	5	90421A170	00000
	3/8"-24	3/8"	9/16"	5/8"	—	5	90421A180	00000
	7/16"-14	7/16"	5/8"	45/64"	—	1	90421A190	0000
	1/2"-13	1/2"	3/4"	13/16"	—	1	90421A210	0000
	5/8"-11	5/8"	15/16"	1"	—	1	90421A220	00000


	3/4"-10	3/4"	1 1/16"	1 5/32"	—	1	90421A230	00000
	M5 × 0.8 mm	5.6 mm	8 mm	10 mm	DIN 1587	5	90428A110	00000
	M6 × 1 mm	5.7 mm	10 mm	12 mm	DIN 1587	5	90428A120	00000
	M8 × 1.25 mm	8.2 mm	13 mm	15 mm	DIN 1587	5	90428A130	00000
	M10 × 1.5 mm	9.7 mm	17 mm	18 mm	DIN 1587	1	90428A140	00000
	M12 × 1.75 mm	12.2 mm	19 mm	22 mm	DIN 1587	1	90428A150	00000


	Black-Oxide 18-8 Stainless Steel



			10-32	3/16"	3/8"	13/32"	—	5	90421A320	00000


			1/4"-20	1/4"	7/16"	15/32"	—	5	90421A340	00000


			Highly Corrosion-Resistant 316 Stainless Steel



					10-24	3/16"	3/8"	13/32"	—	5	93052A110	00000


					10-32	3/16"	3/8"	13/32"	—	5	93052A120	00000
					1/4"-20	1/4"	7/16"	15/32"	—	5	93052A130	00000
					5/16"-18	5/16"	1/2"	17/32"	—	1	93052A140	0000
					3/8"-16	3/8"	9/16"	5/8"	—	1	93052A150	0000
					1/2"-13	1/2"	3/4"	13/16"	—	1	93052A160	00000
					5/8"-11	5/8"	15/16"	1"	—	1	93052A170	00000

Nylon-Insert Cap Nuts

Get the protection of a cap nut with the vibration resistance of a locknut. These nuts not only conceal protruding screw threads, they also have a nylon insert that grips the screw to prevent loosening from moderate vibration. However, the insert may become brittle if exposed to high temperatures. Nuts are reusable a handful of times, but their holding power decreases with each use.

Low-Strength Steel

Rated Grade 2, Class 6, or lower, these nuts 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.

Steel—Best for dry environments since moisture will cause these nuts to rust.

Nylon 6/6 Cap—The nylon cap on these nuts is softer than metal, so it's less likely to scratch surrounding surfaces or parts.

	Thread Dp.	Wd.	Ht.	Fastener Strength Grade/Class	Specs. Met	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	M4 × 0.7 mm	2.3 mm	7 mm	9.6 mm	Class 6	DIN 986	245	50	90582A111	000000


	M5 × 0.8 mm	3.5 mm	8 mm	10.5 mm	Class 6	DIN 986	245	25	90582A112	0000
	M6 × 1 mm	3.9 mm	10 mm	12 mm	Class 6	DIN 986	245	25	90582A113	0000
	M8 × 1.25 mm	5.2 mm	13 mm	14 mm	Class 6	DIN 986	245	25	90582A114	00000
	M10 × 1.5 mm	6.4 mm	16 mm	18 mm	Class 6	DIN 986	245	10	90582A115	00000
	M12 × 1.75 mm	8.3 mm	18 mm	23 mm	Class 6	DIN 986	245	5	90582A116	0000
	M16 × 2 mm	11.3 mm	24 mm	28 mm	Class 6	DIN 986	245	1	90582A117	0000
	M20 × 2.5 mm	13.5 mm	30 mm	35 mm	Class 6	DIN 986	245	1	90582A118	0000


	Zinc-Plated Steel with Nylon 6/6 Cap



			8-32	9/64"	11/32"	23/64"	SAE Grade 2	—	250	25	98190A130	0000


			10-24	9/64"	3/8"	23/64"	SAE Grade 2	—	250	25	98190A150	0000
			10-32	9/64"	3/8"	23/64"	SAE Grade 2	—	250	25	98190A170	0000
			1/4"-20	7/32"	7/16"	31/64"	SAE Grade 2	—	250	25	98190A190	0000
			5/16"-18	1/4"	1/2"	1/2"	SAE Grade 2	—	250	10	98190A210	0000
			3/8"-16	21/64"	9/16"	5/8"	SAE Grade 2	—	250	25	98190A111	00000


			Steel with Nylon 6/6 Cap



					8-32	9/64"	11/32"	23/64"	SAE Grade 2	—	250	25	98190A112	0000


					10-32	9/64"	3/8"	23/64"	SAE Grade 2	—	250	25	98190A113	0000
					1/4"-20	7/32"	7/16"	31/64"	SAE Grade 2	—	250	25	98190A114	0000
					1/4"-28	7/32"	7/16"	31/64"	SAE Grade 2	—	250	25	98190A115	0000
					5/16"-24	1/4"	1/2"	1/2"	SAE Grade 2	—	250	25	98190A116	0000
					3/8"-24	21/64"	9/16"	5/8"	SAE Grade 2	—	250	25	98190A117	00000

Medium-Strength Steel

About twice as strong as low-strength steel, these Grade 5 nuts fasten 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.

Nylon 6/6 Cap—The nylon cap on these nuts is softer than metal, so it's less likely to scratch surrounding surfaces or parts.

	Thread Dp.	Wd.	Ht.	Fastener Strength Grade/Class	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Plated Steel with Nylon 6/6 Cap



	3/8"-24	21/64"	9/16"	5/8"	SAE Grade 5	250	10	98190A270	000000

Distorted-Thread Cap Nuts

For a stronger hold than nylon-insert cap nuts, these have irregularly shaped threads that grip the screw to resist loosening. The threads prevent the nut from backing out in high-vibration applications, but 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. They have a smooth, rounded head that conceals and protects protruding screw threads while creating a finished look. Nuts are not reusable.

Stainless Steel

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

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



	4-40	5/32"	1/4"	1/4"	10	90507A209	000000


	6-32	5/32"	5/16"	11/32"	10	90507A210	00000
	8-32	5/32"	5/16"	11/32"	10	90507A215	00000
	10-24	3/16"	3/8"	13/32"	10	90507A220	00000
	10-32	3/16"	3/8"	13/32"	10	90507A225	00000
	1/4"-20	1/4"	7/16"	15/32"	10	90507A230	00000
	1/4"-28	1/4"	7/16"	15/32"	10	90507A235	00000
	5/16"-18	5/16"	1/2"	17/32"	5	90507A240	00000
	5/16"-24	5/16"	1/2"	17/32"	5	90507A245	00000
	3/8"-16	3/8"	9/16"	5/8"	5	90507A250	00000
	3/8"-24	3/8"	9/16"	5/8"	5	90507A255	00000


	7/16"-14	7/16"	5/8"	11/16"	1	90507A275	0000
	7/16"-20	7/16"	5/8"	11/16"	1	90507A276	0000
	1/2"-13	1/2"	3/4"	13/16"	1	90507A033	00000
	1/2"-20	1/2"	3/4"	13/16"	1	90507A044	00000
	5/8"-11	19/32"	1"	63/64"	1	90507A260	0000
	3/4"-10	11/16"	1 1/16"	1 3/16"	1	90507A270	0000


	Highly Corrosion-Resistant 316 Stainless Steel



			8-32	5/32"	5/16"	11/32"	1	90431A110	0000


			10-24	3/16"	3/8"	13/32"	1	90431A120	0000
			10-32	3/16"	3/8"	13/32"	1	90431A130	0000
			1/4"-20	1/4"	7/16"	15/32"	1	90431A140	0000
			5/16"-18	5/16"	1/2"	17/32"	1	90431A150	0000
			3/8"-16	3/8"	9/16"	5/8"	1	90431A160	0000
			1/2"-13	1/2"	3/4"	13/16"	1	90431A170	00000

Low-Strength Steel

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

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



	6-32	5/32"	5/16"	11/32"	SAE Grade 2	50	90455A110	000000


	8-32	5/32"	5/16"	11/32"	SAE Grade 2	50	90455A120	00000
	10-24	3/16"	3/8"	13/32"	SAE Grade 2	25	90455A130	00000
	10-32	3/16"	3/8"	13/32"	SAE Grade 2	25	90455A140	00000
	1/4"-20	19/64"	7/16"	15/32"	SAE Grade 2	50	90455A160	00000
	5/16"-18	23/64"	1/2"	17/32"	SAE Grade 2	25	90455A170	00000
	3/8"-16	27/64"	9/16"	5/8"	SAE Grade 2	25	90455A180	00000
	1/2"-13	1/2"	3/4"	13/16"	SAE Grade 2	5	90455A150	00000