M3 Jam Nuts | McMaster-Carr

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23 Products

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


	M3 × 0.5 mm	5.5	1.8	ISO Class 04	DIN 439B, ISO 4035	100	000000000	00000

	Steel


			M3 × 0.5 mm	5.5	1.8	__	DIN 439B, ISO 4035	100	000000000	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.

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.

Super-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., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	M3 × 0.5 mm	5.5	1.8	DIN 439B, ISO 4035	100	000000000	000000

	Black-Oxide 18-8 Stainless Steel


			M3 × 0.5 mm	5.5	1.8	DIN 439B, ISO 4035	10	000000000	0000

			Super-Corrosion-Resistant 316 Stainless Steel


					M3 × 0.5 mm	5.5	1.8	DIN 439B, ISO 4035	100	000000000	00000

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.

Nickel-Plated Brass—The nickel plating offers better corrosion resistance than plain brass to stand up to solvents, salt water, and chemicals. The plating can wear off over time, so these nuts are not recommended for applications that experience a lot of friction or wear.

	Wd., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
Brass


	M3 × 0.5 mm	5.5	1.8	DIN 439B, ISO 4035	100	000000000	000000

	Nickel-Plated Brass


			M3 × 0.5 mm	5.5	1.8	DIN 439B, ISO 4035	25	000000000	0000

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.

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	Specs. Met	Pkg. Qty.		Pkg.
Black-Oxide Steel


	M3 × 0.5 mm	5.5	1.8	ISO Class 04	ASTM A108, DIN 439B, ISO 4035	1	000000000	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.

	Wd., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	M3 × 0.35 mm	5.5	1.8	DIN 439B	1	000000000	00000
	M3 × 0.5 mm	5.5	1.8	DIN 439B	1	000000000	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.

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	Specs. Met	Pkg. Qty.		Pkg.
Zinc-Plated Steel


	M3 × 0.5 mm	5.5	3.9	245	ISO 10511	25	000000000	00000

Medium-Strength Steel Thin-Profile Square Nuts

Made of ISO Class 04 steel and about two-thirds the height of standard steel square nuts, these nuts are suitable for most low-clearance fastening applications. Also known as square jam nuts, they’re commonly jammed together to hold each other in place. Their flat, broad sides make them easy to grip with a wrench and keep them from rotating in channels and square holes. Compared to hex nuts, a greater area is in contact with the fastened surface.

Black-Oxide Steel—Black-oxide steel square nuts have a dark surface color and are mildly corrosion resistant in dry environments.

Zinc-Plated Steel—Zinc-plated steel square nuts resist corrosion in wet environments.

DIN 562—These nuts meet DIN 562, an international standard that signifies their material and dimensions are compatible with other products and tools.

	Wd., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
Black-Oxide Steel—ISO Class 04


	M3 × 0.5 mm	5.5	1.8	DIN 562	10	000000000	00000

	Zinc-Plated Steel—ISO Class 04


			M3 × 0.5 mm	5.5	1.8	DIN 562	100	000000000	0000

18-8 Stainless Steel Thin-Profile Square Nuts

Two-thirds the height of typical square nuts and made of 18-8 stainless steel, these metric nuts are designed for use in low-clearance applications in humid, damp, and washdown environments. They’re often called square jam nuts because they can be jammed together to hold each other in place. They’re easily gripped with a wrench due to their flat, broad sides, which also prevent them from rotating in channels and square holes. Compared to hex nuts, a greater area is in contact with the fastened surface. And compared to steel nuts, they’re slightly less strong.

Black-Oxide 18-8 Stainless Steel—Black-oxide 18-8 stainless steel nuts have a dark surface color.

DIN 562—These nuts meet DIN 562, an international standard that signifies their material and dimensions are compatible with other products and tools.

	Wd., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
18-8 Stainless Steel


	M3 × 0.5 mm	5.5	1.8	DIN 562	50	000000000	00000

	Black-Oxide 18-8 Stainless Steel


			M3 × 0.5 mm	5.5	1.8	DIN 562	10	000000000	00000

Knurled-Head Thumb Nuts

Get a good grip on these nuts, even with oily fingers. They have a raised, slip-resistant head, so you can tighten them by hand and make controlled adjustments. Knurled-head nuts have a smaller profile than wing nuts, so they fit in tighter spots.

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.

		Collar, mm
	Thread Size	Dia.	Ht.	Head Dia., mm	Ht., mm	Threading	Specs. Met		Each
18-8 Stainless Steel


		M3 × 0.5 mm	6	5	12	7.5	Fully Threaded	DIN 466	000000000	00000

		Black-Oxide 18-8 Stainless Steel


				M3 × 0.5 mm	6	5	12	7.5	Fully Threaded	DIN 466	000000000	0000

Plastic

Reinforced Acetal—The best plastic for damp and wet environments, acetal won't swell or lose strength if exposed to moisture. These nuts are reinforced with an aluminum threaded insert, so they can handle more torque than other plastic nuts and won't crack during installation.

		Collar, mm
	Thread Size	Dia.	Ht.	Head Dia., mm	Ht., mm	Color	Threading	Insert Material	Pkg. Qty.		Pkg.
Reinforced Acetal


		M3 × 0.5 mm	9.1	1.2	9.6	5.6	Black	Fully Threaded	Aluminum	10	000000000	00000

Flanged Knurled-Head Thumb Nuts

The slip-resistant head is easy to grip, while the flange distributes pressure evenly across the mounting surface without the need for a separate washer. These nuts are often used to secure screws in oversized or irregularly shaped holes since the flange covers a larger area than standard nuts.

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.

Passivated 18-8 Stainless Steel—With an added layer of protection, these nuts stand up to strong acids and other harsh chemicals.

		Collar, mm
	Thread Size	Dia.	Ht.	Head Dia., mm	Ht., mm	Threading		Each
18-8 Stainless Steel


		M3 × 0.5 mm	6	3	8	6	Fully Threaded	000000000	00000
		M3 × 0.5 mm	6	5	16	8	Fully Threaded	000000000	0000

		Black-Oxide 18-8 Stainless Steel


				M3 × 0.5 mm	6	3	8	6	Fully Threaded	000000000	0000

				Passivated 18-8 Stainless Steel


						M3 × 0.5 mm	6	3	8	6	Fully Threaded	000000000	0000

Brass

Zinc-Plated Brass—The zinc plating offers better corrosion resistance than plain brass to stand up to solvents and mild chemicals.

		Collar, mm
	Thread Size	Dia.	Ht.	Head Dia., mm	Ht., mm	Threading		Each
Zinc-Plated Brass


		M3 × 0.5 mm	6	3	8	6	Fully Threaded	000000000	00000