7/16"-20 Locknuts | McMaster-Carr

Filter by

System of Measurement

Nut Type

Fastener Strength Grade/Class

Material

Finish

Zinc Yellow-Chromate Plated

Locking Type

Width

Hex Nut Profile

Thread Type

Height

Thread Spacing

Performance

Fastener Strength Rating

Low

Medium

High

Thread Fit

Unified Standard Class 2B

Unified Standard Class 3B

Thread Direction

RoHS

Flange Diameter

Drive Style

REACH

U.S.–Mexico–Canada Agreement (USMCA) Qualifying

Yes

Export Control Classification Number (ECCN)

EAR99

DFARS Specialty Metals

Compliant

Exempt

Not Compliant

Distorted Thread Type

Center Lock

Top Lock

Sold As

Individual

Insert Maximum Temperature

43 Products

Nylon-Insert Locknuts

Versatile yet economical, these are the most commonly used locknuts. 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-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.

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

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



	7/16"-20	5/8"	29/64"	SAE Grade 8	185	10	97135A245	00000


	Black-Oxide Steel



			7/16"-20	5/8"	29/64"	SAE Grade 8	185	10	97135A422	0000


			Steel



					7/16"-20	5/8"	29/64"	SAE Grade 8	185	25	90630A113	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



	7/16"-20	5/8"	29/64"	SAE Grade 5	185	100	95615A190	000000


	Black-Oxide Steel



			7/16"-20	5/8"	29/64"	SAE Grade 5	185	100	95615A108	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.	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	7/16"-20	5/8"	29/64"	185	100	90640A155	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.

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



	7/16"-20	5/8"	29/64"	185	25	91831A135	000000


	Black-Oxide 18-8 Stainless Steel



			7/16"-20	5/8"	29/64"	185	5	94407A120	00000


			316 Stainless Steel



					7/16"-20	5/8"	29/64"	185	10	90715A034	0000

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

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



	7/16"-20	5/8"	5/16"	SAE Grade 8	Not Rated	25	94945A270	000000


	Black-Oxide Steel



			7/16"-20	5/8"	5/16"	SAE Grade 8	250	10	94945A136	00000

Low-Strength Steel

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



	7/16"-20	5/8"	5/16"	220	100	90566A225	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.

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



	7/16"-20	5/8"	5/16"	220	5	90101A250	00000


	316 Stainless Steel



			7/16"-20	5/8"	5/16"	220	25	97367A136	00000

Mil. Spec. Distorted-Thread Flange Nuts

Not only do these have the strongest hold of all the flange nuts we offer, they are also manufactured and tested to strict U.S. military standards for material and construction. They have irregularly shaped threads that grip the screw to resist loosening in high-vibration applications. The threads prevent the nut from backing out, 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, so they are not reusable. Nuts have a flange that distributes pressure evenly across the mounting surface without the need for a separate washer. They are ideal for securing screws in oversized or irregularly shaped holes since the flange covers a larger area than standard nuts. Also known as collar nuts.

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

Corrosion-Resistant Stainless Steel

Image of Product. Front orientation. Flange Nuts. Mil. Spec. Distorted-Thread Flange Nuts.

High-Temperature A286 Stainless Steel—Stronger than 316 stainless steel and withstand high temperatures up to 1500° F. These nuts resist corrosion from chemicals, such as bleach and chlorine, but they won't hold up to salt water as well as 316 stainless steel.

				Flange
	Thread Size	Wd.	Ht.	Dia.	Thk.	Mil. Spec.	Certificate Type	Pkg. Qty.		Pkg.
High-Temperature A286 Stainless Steel



		7/16"-20	1/2"	21/64"	0.708"	0.04"	NAS1291C7M	Material Certificate	1	98892A115	000000

Serrated Flange Nuts

Serrations bite into material for mild vibration resistance while the flange eliminates the need for a separate washer. These nuts are ideal for securing screws in oversized or irregularly shaped holes since the flange covers a larger area than standard nuts. You can use them again and again without sacrificing strength. However, the serrations may mar the surface of your material. Also known as collar nuts.

Medium-Strength Steel

Rated Grade 5, Grade F, or Class 8, these 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 that creates a finished look. They offer minimal corrosion resistance, so they're best for dry environments.

				Flange
	Thread Size	Wd.	Ht.	Dia.	Thk.	Fastener Strength Grade/Class	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		7/16"-20	11/16"	3/8"	59/64"	0.04"	SAE Grade 5	100	99904A224	000000


		Black-Oxide Steel



				7/16"-20	11/16"	3/8"	59/64"	0.04"	SAE Grade 5	100	99904A215	00000

Low-Strength Steel

About half the strength of medium-strength steel nuts, these 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.

				Flange
	Thread Size	Wd.	Ht.	Dia.	Thk.	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		7/16"-20	11/16"	25/64"	15/16"	0.04"	50	94831A651	000000


		Black-Oxide Steel



				7/16"-20	11/16"	25/64"	15/16"	0.04"	10	93083A115	0000

Top-Lock Distorted-Thread Locknuts

Irregularly shaped threads at the top of these locknuts 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.

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.

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



	7/16"-20	11/16"	3/8"	ASTM Grade C	25	99291A250	00000


	Zinc-Plated Steel



			7/16"-20	11/16"	3/8"	ASTM Grade C	50	92501A528	00000


			Black-Oxide Steel



					7/16"-20	11/16"	3/8"	ASTM Grade C	10	99291A470	0000


					Zinc-Flake-Coated Steel



							7/16"-20	11/16"	3/8"	ASTM Grade C	5	99291A690	00000


							Cadmium-Plated Steel



									7/16"-20	11/16"	3/8"	ASTM Grade C	50	92501A435	00000


									Steel



											7/16"-20	11/16"	3/8"	ASTM Grade C	50	92501A508	0000

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	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	7/16"-20	11/16"	27/64"	SAE Grade 5	25	95065A107	000000


	Black-Oxide Steel



			7/16"-20	11/16"	27/64"	SAE Grade 5	25	90673A114	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



	7/16"-20	11/16"	3/8"	5	90045A465	00000

Distorted-Thread Flange Nuts

The strongest hold of all the flange nuts we offer, these have irregularly shaped threads that grip the screw to resist loosening. The threads prevent the nut from backing out due to high vibration, 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, so they are not reusable. Nuts have a flange that distributes pressure evenly across the mounting surface without the need for a separate washer. They are ideal for securing screws in oversized or irregularly shaped holes since the flange covers a larger area than standard nuts. Also known as collar nuts.

Medium-Strength Steel

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

Black Phosphate-Coated Steel—The dark coating creates both a finished appearance and a barrier against rust that withstands occasional exposure to moisture.

				Flange
	Thread Size	Wd.	Ht.	Dia.	Thk.	Fastener Strength Grade/Class	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		7/16"-20	11/16"	25/64"	15/16"	0.06"	SAE Grade 5	50	90426A370	000000


		Black Phosphate-Coated Steel



				7/16"-20	11/16"	25/64"	15/16"	0.06"	SAE Grade 5	50	90426A250	00000

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.

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



	7/16"-20	5/8"	15/32"	1	94820A310	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.

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

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



	7/16"-20	5/8"	15/32"	1	91839A140	000000

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

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

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



	7/16"-20	11/16"	3/8"	SAE Grade 8	10	90636A057	00000

Low-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



	7/16"-20	11/16"	3/8"	SAE Grade 2	50	90040A135	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.	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	7/16"-20	11/16"	3/8"	10	90047A133	00000

Mil. Spec. Nylon-Insert Locknuts

These locknuts are manufactured and tested to strict U.S. military standards for material and construction. 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

Image of Product. Front orientation. Locknuts. Mil. Spec. Nylon-Insert Locknuts.

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



	7/16"-20	11/16"	15/32"	MS17830-7F, MS21044C7, NASM17830, NASM21044	250	1	96345A765	000000

Two-Piece-Clamp Locknuts for Extreme Vibration

Similar to steel-insert locknuts, these two-piece nuts withstand extreme vibration but are easier to install. Since the two pieces spin freely by hand until you tighten them together with a wrench, they're perfect for extra long screws and threaded rods. You can reuse them a handful of times, but their hold will decrease with repeated use. Also known as drake-style locknuts.

Height includes both nuts once assembled.

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

Steel

These locknuts have equivalent strength to Grade 5 and Class 8 steel nuts. To avoid stripped threads during installation, make sure your screw has a comparable strength rating.

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

	Wd.	Ht.		Each
Steel



	7/16"-20	11/16"	19/32"	90623A180	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.

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



	7/16"-20	5/8"	21/64"	5	94830A540	00000

Locknuts for use with Cotter Pins

Use these locknuts to secure rotating parts subjected to mild vibration, such as the wheels on carts and hand trucks. They’re not recommended for use on parts exposed to high vibration because the pin can shear under prolonged stress. These nuts are reusable, but you'll need a new cotter pin (not included) with each use.

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	For Cotter Pin Dia.	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	7/16"-20	11/16"	3/8"	SAE Grade 5	7/64"	10	97190A130	00000

Low-Strength Steel

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

	Wd.	Ht.	For Cotter Pin Dia.	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	7/16"-20	11/16"	3/8"	3/32"	25	95030A180	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.

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



	7/16"-20	11/16"	21/64"	MS21083C7, NASM21083	250	1	97231A510	000000

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.

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



	7/16"-20	11/16"	15/32"	MS21045-7	1	99638A500	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



	7/16"-20	7/16"	5/8"	11/16"	1	90507A276	00000