5/8"-18 Jam Nuts | McMaster-Carr

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30 Products

About Hex Nuts

Choose a hex nut with the right profile, material, and strength for your application.

Thin-Profile Hex Nuts

About half the height of standard-profile nuts, these fit in spaces with low clearance. You can also use them as jam nuts by threading them against another hex nut to hold it in place.

Medium-Strength Steel

These Grade 5 or Class 04 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.

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

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



	5/8"-18	15/16"	3/8"	SAE Grade 5	ASME B18.2.2	25	94846A535	000000


	Steel



			5/8"-18	15/16"	3/8"	SAE Grade 5	ASME B18.2.2	10	94846A214	0000

High-Strength Steel

Rated Grade 8, Grade C, or Class 10, these nuts are about 25% stronger than medium-strength steel nuts. They are commonly used to fasten components in valves, pumps, motors, and other high-stress applications. 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.

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.

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

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



	5/8"-18	15/16"	3/8"	SAE Grade 8	ASME B18.2.2	10	92053A140	000000


	Zinc-Yellow-Chromate-Plated Steel



			5/8"-18	15/16"	3/8"	SAE Grade 8	ASME B18.2.2	10	93839A835	00000


			Steel



					5/8"-18	15/16"	3/8"	SAE Grade 8	ASME B18.2.2	10	92052A230	00000

Low-Strength Steel

Rated Grade 2, Class 6, or lower, these nuts are about half as strong as medium-strength nuts. They are suitable for light duty fastening applications, such as securing access panels. 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-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.

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

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



	5/8"-18	15/16"	3/8"	SAE Grade 2	25	91078A235	000000


	Black-Oxide Steel



			5/8"-18	1 1/16"	1/4"	—	1	90475A035	0000


			Steel



					5/8"-18	15/16"	3/8"	SAE Grade 2	100	90494A235	00000

Corrosion-Resistant 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.

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.

Highly Corrosion-Resistant 316 Stainless Steel—Superior to 18-8 stainless steel, these nuts won't degrade when exposed to harsh weather, salt water, and most chemicals.

Highly Corrosion-Resistant Black-Oxide 316 Stainless Steel—Combines a finished appearance with the rust resistance of 316 stainless steel. Even if the coating wears off, these nuts will hold up in just about any environment, including salt water and most chemicals.

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



	5/8"-18	15/16"	3/8"	Material Certificate	10	91847A545	00000


	Black-Oxide 18-8 Stainless Steel



			5/8"-18	15/16"	3/8"	—	5	98514A150	0000


			Highly Corrosion-Resistant 316 Stainless Steel



					5/8"-18	15/16"	3/8"	—	5	94805A231	0000


					Highly Corrosion-Resistant Black-Oxide 316 Stainless Steel



							5/8"-18	15/16"	3/8"	—	1	90831A210	0000

Brass

Brass—Conductive and nonmagnetic, brass nuts are commonly used to secure electrical equipment, such as circuit board assemblies and mounting brackets, inside enclosures. They're also softer than most metals, so they won't damage other fastening components.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Brass



	5/8"-18	15/16"	3/8"	5	92174A460	000000

Left-Hand-Thread Hex Nuts

These nuts tighten when turned to the left. Use them with left-hand rods and screws to prevent counterclockwise-moving parts from loosening.

Corrosion-Resistant Stainless Steel

Highly Corrosion-Resistant 316 Stainless Steel—Superior to 18-8 stainless steel, these nuts won't degrade when exposed to harsh weather, salt water, and most chemicals.

	Wd.	Ht.	Pkg. Qty.		Pkg.
Highly Corrosion-Resistant 316 Stainless Steel



	5/8"-18	15/16"	35/64"	1	95355A263	000000

Left-Hand-Thread Thin-Profile Hex Nuts

These nuts tighten when turned to the left. Use them with left-hand rods and screws to prevent counterclockwise-moving parts from loosening. About half the height of standard-profile nuts, these fit in spaces with low clearance. You can also use them as jam nuts by threading them against another hex nut to hold it in place.

Medium-Strength Steel

These Grade 5 or Class 04 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.	Ht.	Fastener Strength Grade/Class	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	5/8"-18	15/16"	3/8"	SAE Grade 5	10	99612A159	00000

Low-Strength Steel

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

	Wd.	Ht.	Fastener Strength Grade/Class	Pkg. Qty.		Pkg.
Steel



	5/8"-18	15/16"	3/8"	SAE Grade 2	10	90083A235	000000

Corrosion-Resistant 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.

Highly Corrosion-Resistant 316 Stainless Steel—Superior to 18-8 stainless steel, these nuts won't degrade when exposed to harsh weather, salt water, and most chemicals.

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



	5/8"-18	15/16"	3/8"	1	94450A315	00000


	Highly Corrosion-Resistant 316 Stainless Steel



			5/8"-18	15/16"	3/8"	1	93031A176	00000

Brass

	Wd.	Ht.		Each
Brass



	5/8"-18	15/16"	3/8"	92117A780	000000

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.

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

	Wd.	Ht.	Fastener Strength Grade/Class	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Yellow-Chromate-Plated Steel



	5/8"-18	15/16"	25/64"	SAE Grade 8	250	5	94945A122	00000


	Zinc-Plated Steel



			5/8"-18	15/16"	25/64"	SAE Grade 8	220	5	94945A230	0000


			Black-Oxide Steel



					5/8"-18	15/16"	25/64"	SAE Grade 8	250	5	94945A113	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.	Ht.	Fastener Strength Grade/Class	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	5/8"-18	15/16"	25/64"	SAE Grade 5	220	5	91342A220	000000

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



	5/8"-18	15/16"	25/64"	220	50	90566A235	000000

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.	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	5/8"-18	15/16"	25/64"	220	1	90101A260	00000

Mil. Spec. Thin-Profile Hex Nuts

These nuts are manufactured and tested to strict U.S. military standards for material and construction. About half the height of standard-profile nuts, they fit in spaces with low clearance. You can also use them as jam nuts by threading them against another hex nut to hold it in place.

Corrosion-Resistant 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.

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



	5/8"-18	15/16"	3/8"	Fed. Spec. FF-N-836, MS35691-55	1	92101A104	000000

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.

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.

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

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



	5/8"-18	15/16"	13/32"	1	94830A565	00000


	Steel



			5/8"-18	15/16"	13/32"	1	94830A137	0000

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



	5/8"-18	15/16"	13/32"	1	94140A162	000000

Mil. Spec. Thin-Profile Nylon-Insert Locknuts

These locknuts are manufactured and tested to strict U.S. military standards for material and construction. They are about half the height of standard-profile locknuts to 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.

Certificates with a traceable lot number are available for these products. Download certificates from ORDER HISTORY after your order ships.

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.	Mil. Spec.	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	5/8"-18	15/16"	13/32"	MS21083C10, NASM21083	250	1	97231A520	000000