M4 Locknuts | McMaster-Carr

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38 Products

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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

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

Rated Grade 8 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.

Black-Corrosion-Resistant-Coated Steel—The coating has been tested to extreme standards, including 1,000 hours of salt spray resistance, to hold up in wet and outdoor environments. Also known as black luster.

Large Pack—Priced at least 30% lower per locknut than small packs.

							Small Pack			Large Pack
	Thread Size	Wd., mm	Ht., mm	Fastener Strength Grade/Class	Insert Max. Temp., ° F	Certificate Type	Pkg. Qty.		Pkg.	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		M4 × 0.7 mm	7	5	Class 10	185	Material Certificate	100	94645A101	000000	2,000	94645A208	0000000


		Black-Corrosion-Resistant-Coated Steel



				M4 × 0.7 mm	7	5	Class 10	185	—	5	90237A110	00000	—	———	0

Medium-Strength Steel

These Grade 5, Grade C, 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-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.

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

							Small Pack
	Thread Size	Wd., mm	Ht., mm	Fastener Strength Grade/Class	Insert Max. Temp., ° F	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Yellow-Chromate-Plated Steel



		M4 × 0.7 mm	7	5	Class 8	185	Material Certificate	100	90576A812	000000


		Zinc-Plated Steel



				M4 × 0.7 mm	7	5	Class 8	185	Material Certificate	100	90576A103	0000


				Black-Corrosion-Resistant-Coated Steel



						M4 × 0.7 mm	7	5	Class 8	185	—	5	90819A111	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., mm	Ht., mm	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	M4 × 0.7 mm	7	5	185	100	90631A112	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.

Large Pack—Priced at least 30% lower per locknut than small packs.

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

						Small Pack			Large Pack
	Thread Size	Wd., mm	Ht., mm	Insert Max. Temp., ° F	Certificate Type	Pkg. Qty.		Pkg.	Pkg. Qty.		Pkg.
18-8 Stainless Steel



		M4 × 0.7 mm	7	5	185	Material Certificate	100	93625A150	00000	2,000	93625A122	000000


		Black-Oxide 18-8 Stainless Steel



				M4 × 0.7 mm	7	5	185	Material Certificate	10	93625A224	0000	500	93625A131	000000


				316 Stainless Steel



						M4 × 0.7 mm	7	5	185	Material Certificate	50	94205A230	0000	—	———	0

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.

Low-Strength Steel

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

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



	M4 × 0.7 mm	7	5	245	25	90453A112	00000

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

Image of Product. Bottom orientation. Flange Nuts. Serrated Flange Nuts.

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.

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

				Flange, mm
	Thread Size	Wd., mm	Ht., mm	Dia.	Thk.	Fastener Strength Grade/Class	Specs. Met	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		M4 × 0.7 mm	7	4.6	10	0.4	Class 8	DIN 6923	Material Certificate	100	96194A201	00000


		Zinc-Yellow-Chromate-Plated Steel



				M4 × 0.7 mm	7	4.2	10.5	0.9	Class 8	DIN 6923, ISO 4161	—	50	96194A110	00000


				Black-Oxide Steel



						M4 × 0.7 mm	7	4.6	10	0.4	Class 8	DIN 6923	Material Certificate	100	94920A110	0000


						Steel



								M4 × 0.7 mm	7	4.6	10	0.4	Class 8	DIN 6923	—	100	94920A105	0000

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—Our most corrosion-resistant flange nuts, these hold up in just about any environment, including harsh weather, salt water, and most chemicals.

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

				Flange, mm
	Thread Size	Wd., mm	Ht., mm	Dia.	Thk.	Specs. Met	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



		M4 × 0.7 mm	7	4.65	10	1	DIN 6923	Material Certificate	100	97400A380	000000


		Highly Corrosion-Resistant 316 Stainless Steel



				M4 × 0.7 mm	7	4.65	10	1	DIN 6923	Material Certificate	25	91343A106	00000

Nylon-Insert Flange Nuts

A nylon insert grips the screw for a stronger hold than a serrated flange, without damaging threads or marring the surface of your material. However, the insert may become brittle if exposed to high temperatures. These nuts have a flange that distributes pressure evenly across the mounting surface, so you don't need 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. You can reuse them a handful of times, but their holding power will decrease with each use. 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. Nylon-Insert Flange Nuts.

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.

				Flange, mm
	Thread Size	Wd., mm	Ht., mm	Dia.	Thk.	Certificate Type	Insert Max. Temp., ° F	Pkg. Qty.		Pkg.
18-8 Stainless Steel



		M4 × 0.7 mm	7	6.1	10.2	1.2	Material Certificate	250	10	94710A101	000000

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.

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

Medium-Strength Steel

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	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	M4 × 0.7 mm	7	4.2	Class 8	Material Certificate	100	93795A205	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., mm	Ht., mm	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	M4 × 0.7 mm	7	3.2	Material Certificate	25	90045A111	000000

Locknuts with External-Tooth Lock Washer

To save on assembly time, these locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand. Once the nut is against your material surface, tighten it down with a wrench or socket to get the teeth to bite. Although these nuts install more quickly than nylon-insert locknuts, they don't hold up as well against vibration and can mar your material. As long as the washer stays intact, you can reuse them. Also known as Keps and K-lock nuts.

Medium-Strength Steel

Image of Product. Front orientation. ZoomedIn view. Locknuts. Locknuts with External-Tooth Lock Washer.

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

Black-Zinc-Plated Steel—The dark zinc plating withstands occasional exposure to moisture while creating a finished look.

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

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



	M4 × 0.7 mm	7	4.1	Class 8	8.5	Material Certificate	100	93825A120	000000


	Black-Zinc-Plated Steel



			M4 × 0.7 mm	7	4.1	Class 8	8.5	Material Certificate	100	93825A220	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., mm	Ht., mm	Washer OD, mm	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	M4 × 0.7 mm	7	4.1	8.2	Material Certificate	50	90923A219	000000


	Black-Oxide 18-8 Stainless Steel



			M4 × 0.7 mm	7	4.1	8.2	—	25	90923A232	00000

High-Profile Nylon-Insert Locknuts

Slightly taller than standard-profile locknuts, these have a larger gripping area so your wrench or socket won't slip off as you tighten them. They're often used in vehicles and machinery where fasteners can be difficult to reach. 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.

Medium-Strength Steel

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



	M4 × 0.7 mm	7	5.3	Class 8	220	100	97131A110	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., mm	Ht., mm	Insert Max. Temp., ° F	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	M4 × 0.7 mm	7	5.3	220	Material Certificate	25	93625A111	00000


	316 Stainless Steel



			M4 × 0.7 mm	7	5.3	220	—	10	94205A151	0000

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.

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



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

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.

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., mm	Ht., mm	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	M4 × 0.7 mm	7	6	1	94560A112	00000


	316 Stainless Steel



			M4 × 0.7 mm	7	6	1	94560A130	0000

Locknuts with Spring-Lock Washer

The curved, spring-like washer grips surfaces more tightly than tooth-lock washers for better vibration resistance. These locknuts also install just as quickly since you can twist them into place by hand. Once the nut is against your material, tighten it down with a wrench or socket. The washer's smooth edges won't mar the surface like teeth can. As long as the washer stays intact, you can reuse these locknuts.

Medium-Strength Steel

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.

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



	M4 × 0.7 mm	7	4.2	Class 8	10	100	91270A310	000000


	Black-Oxide Steel



			M4 × 0.7 mm	7	4.2	Class 8	10	50	91270A270	00000

Press-Fit Locknuts for Sheet Metal

The nylon insert inside these nuts grips screws so they won't back out or loosen. Use them to keep thin parts fastened on engines and other vibrating machinery.

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

18-8 Stainless Steel—The choice for wet and outdoor environments, these nuts resist rust and mild chemicals.

	For Maximum Panel Hardness	Head Ht., mm	Flange Dia., mm	PEM® Part No.	Pkg. Qty.		Pkg.
Nylon-Insert Locking







	Zinc-Plated Steel

	M4 x 0.7 mm	7.5	1.5	Brinell 125, Rockwell B70	4	8.5	PL-M4-ZI	10	91835A106	00000




			18-8 Stainless Steel

			M4 x 0.7 mm	7.5	1.5	Brinell 125, Rockwell B70	4	8.5	PLC-M4	5	91835A126	0000

Self-Aligning Press-Fit Locknuts for Sheet Metal

Fasten together unaligned parts and keep screws in place. The threaded hole within these press-fit nuts shifts up to .01" in any direction, so you can fasten together thin panels with off-center holes. The irregularly shaped threads tightly grip screws to prevent them from loosening or backing out under vibration.

18-8 Stainless Steel—The choice for wet and outdoor environments, these nuts resist rust and mild chemicals.

					Head, mm		Barrel, mm
	Thread Size	Drill Bit Size, mm	For Min. Panel Thk., mm	For Maximum Panel Hardness	OD	Ht.	Dia.	Ht.	PEM® Part No.	Pkg. Qty.		Pkg.
Distorted-Thread Locking







				18-8 Stainless Steel

				M4 x 0.7 mm	9.4	0.97	Brinell 125, Rockwell B70	11.18	0.97	4.8	5.3	LAC-M4-1MD	5	93177A240	000000


				M4 x 0.7 mm	9.4	1.38	Brinell 125, Rockwell B70	11.18	1.38	4.8	5.3	LAC-M4-2MD	5	93177A250	00000