M20 Jam Nuts | McMaster-Carr

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33 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.

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.

Blue Dyed Steel—These metric-sized nuts have a distinctive blue color, so you can easily tell them apart from inch nuts.

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



	M20 × 1.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	90326A145	00000


	M20 × 2.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	90695A130	00000


	Zinc-Yellow-Chromate-Plated Steel



			M20 × 1.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	93737A117	0000


			M20 × 2.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	95027A119	00000


			Steel



					M20 × 1.5 mm	30	9	—	DIN 936	—	10	90364A109	00000


					M20 × 1.5 mm	30	10	Class 04	DIN 439B, ISO 4035	Material Certificate with Traceable Lot Number	10	90326A215	0000
					M20 × 2 mm	30	9	—	DIN 936	—	10	90364A108	00000
					M20 × 2.5 mm	30	9	—	DIN 936	—	10	90370A108	00000
					M20 × 2.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	94168A119	0000


					Blue Dyed Steel



							M20 × 2.5 mm	30	10	Class 04	DIN 439B, ISO 4035	—	10	96276A810	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.

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



	M20 × 1.5 mm	30	9	DIN 936	1	97013A113	00000


	M20 × 1.5 mm	30	10	DIN 439B, ISO 4035	1	91938A145	0000
	M20 × 2 mm	30	10	DIN 439B, ISO 4035	5	91938A187	00000
	M20 × 2.5 mm	30	9	DIN 936	1	90381A106	0000
	M20 × 2.5 mm	30	10	DIN 439B, ISO 4035	5	90710A045	00000


	Black-Oxide 18-8 Stainless Steel



			M20 × 1.5 mm	30	10	DIN 439B, ISO 4035	1	97013A133	0000


			Highly Corrosion-Resistant 316 Stainless Steel



					M20 × 2 mm	30	10	DIN 439B, ISO 4035	1	97289A132	0000


					M20 × 2.5 mm	30	9	DIN 936	1	97289A117	0000
					M20 × 2.5 mm	30	10	DIN 439B, ISO 4035	1	93935A365	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., mm	Ht., mm	Specs. Met	Pkg. Qty.		Pkg.
Brass



	M20 × 2.5 mm	30	9	DIN 936	1	97057A150	00000

Steel Hex Panel Nuts

Fasten these panel nuts with a wrench for more torque while tightening than knurled panel nuts. Also known as dress nuts, they're extremely thin for use in tight spaces such as electrical panels.

Metric Thread About Metric Thread

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

	Wd., mm	Ht., mm	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	M20 × 1.5 mm	27	6	1	91862A715	00000

Shock Absorber Mounting Nuts

Hex Nuts

Use Mounting Blocks for Shock Absorbers (not included) to mount and secure threaded-body shock absorbers.

		Steel
	Thread Size		Each
Hex Nuts



		M20 × 1.5 mm	9530K82	00000

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



	M20 × 2.5 mm	30	14.9	245	ISO 10511	1	90453A122	00000

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	Certificate Type	Pkg. Qty.		Pkg.
Black-Oxide Steel



	M20 × 1.5 mm	30	10	Class 04	ASTM A108, DIN 439B, ISO 4035	Material Certificate with Traceable Lot Number	1	90519A839	000000


	M20 × 2.5 mm	30	10	Class 04	ASTM A108, DIN 439B, ISO 4035	—	1	90519A822	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.

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



	M20 × 1.5 mm	30	10	DIN 439B	Material Certificate with Traceable Lot Number	1	94450A575	000000


	M20 × 2.5 mm	30	10	DIN 439, ISO 4035	—	1	94450A124	0000


	Highly Corrosion-Resistant 316 Stainless Steel



			M20 × 1.5 mm	30	10	DIN 439B, ISO 4035	—	1	93031A139	00000

Metric Lead Screws and Nuts

Found in hand-powered clamps, vises, grates, doors, and work tables, lead screws and nuts have broad, square threads that are well suited for quick assembly, high clamping forces, and lifting and lowering heavy objects. To ensure compatibility, please select components that have the same thread direction, size, and number of thread starts. Class 7e and 7H components are compatible.

Hex Nuts—Right-Hand Thread

Hex nuts fasten and position lead screw components.

Travel Distance per Turn—Travel distance per turn, also known as screw lead, is the distance a nut moves with one revolution of the lead screw.

	Thread Type	Ht., mm	Wd., mm	No. of Thread Starts	Speed Ratio	Travel Distance per Turn, mm	Thread Fit	Fastener Strength Grade/Class	Hardness	Tensile Strength		Each
Carbon Steel



	M20 × 4 mm	Metric Trapezoidal	20	31.75	1	1:1	4	Metric Trapezoidal Class 7H	SAE Grade 2	Not Rated	Not Rated	94353A200	000000

Square Nuts—Right-Hand Thread

Square nuts fasten and position lead screw components. Square nuts have large sides, which make them easier to grip with a wrench than hex nuts and keep them from rotating in channels and square holes.

360 Brass—360 brass components have excellent machinability and good corrosion resistance.

Travel Distance per Turn—Travel distance per turn, also known as screw lead, is the distance a nut moves with one revolution of the lead screw.

	Thread Type	Ht., mm	Wd., mm	No. of Thread Starts	Speed Ratio	Travel Distance per Turn, mm	Thread Fit	Hardness	Tensile Strength		Each
360 Brass



	M20 × 4 mm	Metric Trapezoidal	50	38	1	1:1	4	Metric Trapezoidal Class 7H	Not Rated	Not Rated	94353A314	0000000

Bearing Nuts

Carbon Steel

Stepped Face

Often paired with spring lock washers to strengthen their hold, these bearing nuts—also known as shaft nuts—keep vibration from shifting bearings, bushings, pulleys, and gears on your threaded shaft or spindle. They have slotted sides, so you can tighten and loosen them with a spanner wrench or spanner socket.

Carbon Steel—Carbon steel bearing nuts are strong and resist wear.

Stepped Face—Use stepped-face bearing nuts with DIN 462 spring lock washers. You can also use them in pairs or with other bearing nuts. For the nut closer to the bearing, position the stepped face towards the bearing. All meet DIN standards for bearing lockout dimensions.

Thread Spacing—When choosing your thread spacing, consider the precision of your application. The finer the threads, the more control you have when making adjustments.

	Nuts								Bearing Lock Washers
	Thread
	Size	Spacing	OD, mm	Wd., mm	Specs. Met	For Lock Washer Specs. Met		Each		Each
Carbon Steel







				Stepped Face

				M20 × 1.5 mm	Extra Fine	36	8	DIN 1804	DIN 462	3564N16	000000	90407A118	00000

Thin-Profile Bearing Nuts

Used in pairs or with another bearing nut, these thin-profile nuts—often called shaft nuts—hold bearings, bushings, pulleys, and gears in place on your threaded shaft or spindle. Threading two nuts tightly against each other makes it harder for vibration to loosen your assembly than if you used only one nut. For the nut closer to the bearing, position the stepped face towards the bearing. These thin-profile nuts have holes on the side, so you can tighten and loosen them with a pin spanner wrench. All meet DIN 1816, an international standard for bearing locknut dimensions.

Carbon Steel—Carbon steel bearing nuts are strong and resist wear.

Thread Spacing—When choosing your thread spacing, consider the precision of your application. The finer the threads, the more control you have when making adjustments.

	Thread
	Size	Spacing	OD, mm	Wd., mm	Specs. Met		Each
Carbon Steel







				Stepped Face

				M20 × 1.5 mm	Extra Fine	36	8	DIN 1816	3549N16	000000