Star Hex Nuts | McMaster-Carr

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For Cotter Pin Diameter

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159 Products

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Lock Washer

Twist into place by hand to save on assembly time

61 products

Cotter Pin

Secure rotating parts subjected to mild vibration, such as wheels on carts

98 products

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Corrosion Resistant

Won't rust in wet and outdoor environments

43 products

Hex Nut Profile

Standard

The most common profile of locknut

156 products

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.

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-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.

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



	M3 × 0.5 mm	5.5	3.3	Class 8	7.1	—	100	93825A110	000000


	M4 × 0.7 mm	7	4.1	Class 8	8.5	Material Certificate	100	93825A120	00000
	M5 × 0.8 mm	8	5.2	Class 8	9.5	Material Certificate	100	93825A130	00000
	M6 × 1 mm	10	6.2	Class 8	12	Material Certificate	100	93825A140	00000
	M8 × 1.25 mm	13	8.5	Class 8	15.5	Material Certificate	25	93825A160	0000
	M10 × 1.5 mm	17	9.7	Class 8	20.1	Material Certificate	10	93825A170	00000


	Black-Zinc-Plated Steel



			M3 × 0.5 mm	5.5	3	Class 8	7.1	—	100	93825A210	00000


			M4 × 0.7 mm	7	4.1	Class 8	8.5	Material Certificate	100	93825A220	00000
			M5 × 0.8 mm	8	5.2	Class 8	9.5	—	100	93825A230	00000
			M6 × 1 mm	10	6.2	Class 8	12	Material Certificate	50	93825A240	00000
			M8 × 1.25 mm	13	8.5	Class 8	15.5	Material Certificate	25	93825A250	00000
			M10 × 1.5 mm	17	9.7	Class 8	20.1	—	10	93825A260	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.

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

	Wd.	Ht.	Washer OD	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	4-40	1/4"	7/64"	0.281"	Material Certificate	100	90675A005	00000


	5-40	5/16"	9/64"	0.344"	—	100	90675A245	0000
	6-32	5/16"	9/64"	0.344"	Material Certificate	100	90675A007	0000
	8-32	11/32"	5/32"	0.375"	Material Certificate	100	90675A009	0000
	10-24	3/8"	5/32"	0.406"	Material Certificate	100	90675A011	0000
	10-32	3/8"	5/32"	0.406"	Material Certificate	100	90675A195	0000
	12-24	7/16"	3/16"	0.5"	—	50	90675A255	0000
	1/4"-20	7/16"	15/64"	0.5"	Material Certificate	100	90675A029	0000
	1/4"-28	7/16"	15/64"	0.5"	—	100	90675A215	0000
	5/16"-18	1/2"	21/64"	0.578"	Material Certificate	100	90675A030	00000
	5/16"-24	1/2"	5/16"	0.592"	—	50	90675A225	00000


	3/8"-16	9/16"	25/64"	0.656"	—	100	90675A031	00000
	3/8"-24	9/16"	25/64"	0.656"	—	100	90675A235	00000
	1/2"-13	3/4"	31/64"	0.891"	—	10	90675A265	0000


	Black-Zinc-Plated Steel



			4-40	1/4"	1/8"	0.281"	Material Certificate	100	90328A101	0000


			6-32	5/16"	9/64"	0.344"	Material Certificate	100	90328A102	0000
			8-32	11/32"	5/32"	0.375"	Material Certificate	100	90328A103	0000
			10-24	3/8"	5/32"	0.406"	—	100	90328A104	0000
			10-32	3/8"	5/32"	0.406"	—	100	90328A105	0000
			1/4"-20	7/16"	7/32"	0.5"	—	100	90328A106	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.

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



	4-40	1/4"	1/8"	0.281"	Material Certificate	100	96278A005	000000


	4-48	1/4"	1/8"	0.281"	—	100	96278A101	00000
	6-32	5/16"	9/64"	0.344"	Material Certificate	100	96278A007	00000
	8-32	11/32"	11/64"	0.375"	Material Certificate	100	96278A009	00000
	10-24	3/8"	11/64"	0.406"	Material Certificate	100	96278A011	00000
	10-32	3/8"	11/64"	0.406"	Material Certificate	100	96278A411	00000
	12-24	7/16"	11/64"	0.506"	—	50	96278A111	00000
	1/4"-20	7/16"	15/64"	0.5"	—	50	96278A511	00000
	1/4"-28	7/16"	15/64"	0.5"	—	50	96278A515	00000
	5/16"-18	1/2"	21/64"	0.578"	Material Certificate	25	96278A519	00000
	5/16"-24	1/2"	21/64"	0.578"	—	25	96278A523	00000


	3/8"-16	9/16"	25/64"	0.656"	Material Certificate	25	96278A527	00000
	3/8"-24	9/16"	25/64"	0.656"	—	10	96278A531	0000
	1/2"-13	3/4"	7/16"	0.898"	—	10	96278A112	0000
	M3 × 0.5 mm	5.5 mm	3.3 mm	6.5 mm	Material Certificate	50	90923A216	00000
	M4 × 0.7 mm	7 mm	4.1 mm	8.2 mm	Material Certificate	50	90923A219	00000
	M5 × 0.8 mm	8 mm	5.2 mm	9.5 mm	Material Certificate	25	90923A222	0000
	M6 × 1 mm	10 mm	6.2 mm	11.5 mm	Material Certificate	25	90923A227	0000
	M8 × 1.25 mm	13 mm	8.5 mm	15.1 mm	Material Certificate	5	90923A241	0000
	M10 × 1.5 mm	17 mm	9.7 mm	19.2 mm	Material Certificate	5	90923A282	00000


	Black-Oxide 18-8 Stainless Steel



			M3 × 0.5 mm	5.5 mm	3.3 mm	6.5 mm	—	25	90923A231	0000


			M4 × 0.7 mm	7 mm	4.1 mm	8.2 mm	—	25	90923A232	00000
			M5 × 0.8 mm	8 mm	5.2 mm	9.5 mm	—	25	90923A233	00000
			M6 × 1 mm	10 mm	6.2 mm	11.5 mm	—	25	90923A234	00000

Assortments of Locknuts with External-Tooth Lock Washer

With a range of sizes on hand, you can use these assortments to fasten a variety of parts. These locknuts combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. 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.

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 locknuts resist rust. However, they won't hold up to the harsh chemicals that 316 stainless steel can.

	Locknuts Included	Container Type		Each
Zinc-Plated Steel



	600	4-40 (100 Pieces) 6-32 (100 Pieces) 8-32 (100 Pieces) 10-24 (100 Pieces) 10-32 (100 Pieces) 1/4"-20 (100 Pieces)	Plastic Box	90740A106	000000


	18-8 Stainless Steel



			600	4-40 (100 Pieces) 6-32 (100 Pieces) 8-32 (100 Pieces) 10-24 (100 Pieces) 10-32 (100 Pieces) 1/4"-20 (100 Pieces)	Plastic Box	90625A500	00000

Narrow-Profile Locknuts with External-Tooth Lock Washer

Since they're about 20% narrower, these locknuts fit in tight spaces where standard-profile nuts won't fit. They combine a hex nut with a free-spinning lock washer, so you can twist them into place by hand and save on assembly time. 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.

Low-Strength Steel

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

	Wd.	Ht.	Washer OD	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Plated Steel



	6-32	1/4"	1/8"	0.281"	—	100	90413A101	000000


	8-32	5/16"	9/64"	0.344"	Material Certificate	100	90413A102	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.	Washer OD	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	6-32	1/4"	1/8"	0.287"	Material Certificate	100	96278A113	000000

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

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.

	Thread Size	Wd.	Ht.	Fastener Strength Grade/Class	For Cotter Pin Dia.	Certificate Type	Pkg. Qty.		Pkg.
Zinc-Plated Steel



		1/4"-20	7/16"	7/32"	SAE Grade 5	1/16"	—	25	97190A005	000000


		1/4"-28	7/16"	7/32"	SAE Grade 5	1/16"	—	10	97190A110	0000
		5/16"-18	1/2"	17/64"	SAE Grade 5	5/64"	—	25	97190A010	00000
		3/8"-16	9/16"	21/64"	SAE Grade 5	7/64"	—	25	97190A015	00000
		3/8"-24	9/16"	21/64"	SAE Grade 5	7/64"	—	10	97190A120	00000
		7/16"-14	11/16"	3/8"	SAE Grade 5	7/64"	—	25	97190A020	00000
		7/16"-20	11/16"	3/8"	SAE Grade 5	7/64"	—	10	97190A130	0000
		1/2"-13	3/4"	7/16"	SAE Grade 5	7/64"	—	10	97190A025	0000
		1/2"-20	3/4"	7/16"	SAE Grade 5	7/64"	Material Certificate	10	97190A140	00000
		9/16"-12	7/8"	31/64"	SAE Grade 5	9/64"	—	10	97190A150	00000
		9/16"-18	7/8"	31/64"	SAE Grade 5	9/64"	—	10	97190A160	00000


		5/8"-11	15/16"	35/64"	SAE Grade 5	5/32"	Material Certificate	10	97190A030	00000
		5/8"-18	15/16"	35/64"	SAE Grade 5	5/32"	Material Certificate	10	97190A170	00000
		3/4"-10	1 1/8"	41/64"	SAE Grade 5	5/32"	—	5	97190A035	00000
		3/4"-16	1 1/8"	41/64"	SAE Grade 5	5/32"	—	5	97190A180	00000
		7/8"-14	1 5/16"	49/64"	SAE Grade 5	3/16"	Material Certificate	1	97190A190	0000
		1"-8	1 1/2"	55/64"	SAE Grade 5	3/16"	—	1	97190A040	0000
		1"-14	1 1/2"	55/64"	SAE Grade 5	3/16"	Material Certificate	1	97190A210	0000
		1 1/4"-7	1 7/8"	1 3/32"	SAE Grade 5	5/16"	—	1	97190A220	0000
		1 1/4"-12	1 7/8"	1 3/32"	SAE Grade 5	5/16"	Material Certificate	1	97190A230	00000
		M6 × 1 mm	10 mm	7.5 mm	Class 8	1.6 mm	—	5	93760A212	0000


		M8 × 1.25 mm	13 mm	9.5 mm	Class 8	2 mm	—	5	93760A222	0000
		M10 × 1.5 mm	17 mm	12 mm	Class 8	2.5 mm	—	5	93760A233	0000
		M12 × 1.75 mm	19 mm	15 mm	Class 8	3.2 mm	Material Certificate	5	93760A317	0000
		M12 × 1.5 mm	19 mm	15 mm	Class 8	3.2 mm	—	5	93760A126	0000
		M14 × 2 mm	22 mm	16 mm	Class 8	3.2 mm	—	1	93760A111	0000
		M14 × 1.5 mm	22 mm	16 mm	Class 8	3.2 mm	—	1	93760A127	0000
		M16 × 2 mm	24 mm	19 mm	Class 8	4 mm	—	5	93760A328	00000
		M16 × 1.5 mm	24 mm	19 mm	Class 8	4 mm	—	10	93760A128	00000
		M18 × 2.5 mm	27 mm	21 mm	Class 8	4 mm	—	1	93760A112	0000
		M20 × 2.5 mm	30 mm	22 mm	Class 8	4 mm	—	5	93760A337	00000


		M24 × 3 mm	36 mm	27 mm	Class 8	5 mm	—	1	93760A340	0000
		M24 × 2 mm	36 mm	27 mm	Class 8	5 mm	Material Certificate	1	93760A129	00000
		M27 × 3 mm	41 mm	30 mm	Class 8	5 mm	—	1	93760A113	00000
		M30 × 3.5 mm	46 mm	33 mm	Class 8	6.3 mm	Material Certificate	1	93760A114	00000


		Steel



				M12 × 1.5 mm	19 mm	15 mm	Class 8	3.2 mm	—	10	93760A131	0000


				M14 × 2 mm	22 mm	16 mm	Class 8	3.2 mm	—	1	93760A115	0000
				M14 × 1.5 mm	22 mm	16 mm	Class 8	3.2 mm	—	1	93760A132	0000
				M16 × 2 mm	24 mm	19 mm	Class 8	4 mm	—	1	93760A116	0000
				M16 × 1.5 mm	24 mm	19 mm	Class 8	4 mm	—	1	93760A133	0000
				M18 × 2.5 mm	27 mm	21 mm	Class 8	4 mm	Material Certificate	1	93760A117	0000
				M20 × 2.5 mm	30 mm	22 mm	Class 8	4 mm	—	1	93760A118	0000
				M24 × 3 mm	36 mm	27 mm	Class 8	5 mm	—	1	93760A119	0000
				M30 × 3.5 mm	46 mm	33 mm	Class 8	6.3 mm	—	1	93760A121	00000
				M36 × 4 mm	55 mm	38 mm	Class 8	6.3 mm	—	1	93760A122	00000
M36 × 3 mm				55 mm	38 mm	Class 8	6.3 mm	—	1	93760A134	00000


M42 × 4.5 mm	65 mm			46 mm	Class 8	8 mm	—	1	93760A123	00000
M48 × 5 mm	75 mm			50 mm	Class 8	8 mm	—	1	93760A124	00000
M56 × 5.5 mm	85 mm			57 mm	Class 8	8 mm	Material Certificate	1	93760A125	00000

Low-Strength Steel

Image of ProductInUse. Front orientation. Locknuts. Locknuts for use with Cotter Pins.

Image of Product. Front orientation. Locknuts. Locknuts for use with Cotter Pins.

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



	1/4"-20	7/16"	7/32"	1/16"	—	50	95030A110	000000


	1/4"-28	7/16"	7/32"	1/16"	—	50	95030A120	00000
	5/16"-18	1/2"	17/64"	5/64"	—	25	95030A130	0000
	5/16"-24	1/2"	17/64"	5/64"	Material Certificate	25	95030A140	0000
	3/8"-16	9/16"	21/64"	7/64"	—	25	95030A150	00000
	3/8"-24	9/16"	21/64"	7/64"	—	25	95030A160	00000
	7/16"-14	11/16"	3/8"	3/32"	—	25	95030A170	00000
	7/16"-20	11/16"	3/8"	3/32"	—	25	95030A180	00000
	1/2"-13	3/4"	7/16"	1/8"	—	25	95030A190	00000
	1/2"-20	3/4"	7/16"	1/8"	—	25	95030A210	00000
	9/16"-12	7/8"	31/64"	7/64"	—	10	95030A220	00000


	9/16"-18	7/8"	31/64"	7/64"	—	5	95030A230	0000
	5/8"-11	15/16"	35/64"	5/32"	—	10	95030A240	0000
	5/8"-18	15/16"	35/64"	5/32"	—	10	95030A250	0000
	3/4"-10	1 1/8"	21/32"	5/32"	—	10	95030A260	00000
	3/4"-16	1 1/8"	21/32"	5/32"	—	10	95030A270	00000
	7/8"-9	1 5/16"	3/4"	5/32"	—	5	95030A280	00000
	7/8"-14	1 5/16"	3/4"	5/32"	—	5	95030A290	00000
	1"-8	1 1/2"	55/64"	3/16"	Material Certificate	5	95030A310	00000
	1"-14	1 1/2"	55/64"	3/16"	—	5	95030A320	00000
	1 1/4"-7	1 7/8"	1 3/32"	9/32"	—	1	95030A350	0000


	1 1/4"-12	1 7/8"	1 1/16"	9/32"	—	1	95030A360	0000
	1 1/2"-6	2 1/4"	1 5/16"	5/16"	—	1	95030A370	00000
	1 1/2"-12	2 1/4"	1 5/16"	5/16"	—	1	95030A380	00000
	1 3/4"-5	2 5/8"	1 1/2"	3/8"	Material Certificate	1	95030A390	00000
	1 3/4"-12	2 5/8"	1 1/2"	3/8"	Material Certificate	1	95030A410	00000
	2"-4 1/2	3"	1 23/32"	3/8"	Material Certificate	1	95030A420	00000
	2"-12	3"	1 23/32"	3/8"	—	1	95030A430	00000


	Black-Oxide Steel



			1 1/2"-12	2 1/4"	1 9/32"	5/16"	—	1	95030A610	00000


			Steel



					1/4"-20	7/16"	7/32"	1/16"	—	25	95030A510	0000


					5/16"-24	1/2"	17/64"	5/64"	—	25	95030A520	0000
					1"-14	1 1/2"	55/64"	3/16"	—	1	95030A530	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.	For Cotter Pin Dia.	Certificate Type	Pkg. Qty.		Pkg.
18-8 Stainless Steel



	10-32	3/8"	1/4"	3/64"	—	5	91853A510	000000


	1/4"-20	7/16"	9/32"	1/16"	—	5	91853A029	0000
	1/4"-28	7/16"	9/32"	1/16"	—	5	91853A515	00000
	5/16"-18	1/2"	21/64"	5/64"	—	5	91853A030	00000
	5/16"-24	1/2"	21/64"	5/64"	—	5	91853A520	00000
	3/8"-16	9/16"	13/32"	3/32"	—	1	91853A031	0000
	3/8"-24	9/16"	13/32"	3/32"	—	1	91853A525	0000
	1/2"-13	3/4"	9/16"	1/8"	Material Certificate	1	91853A033	0000
	1/2"-20	3/4"	9/16"	1/8"	—	1	91853A535	0000
	5/8"-11	15/16"	23/32"	5/32"	Material Certificate	1	91853A035	0000
	5/8"-18	15/16"	23/32"	5/32"	Material Certificate	1	91853A545	0000


	3/4"-10	1 1/8"	13/16"	5/32"	Material Certificate	1	91853A036	0000
	3/4"-16	1 1/8"	13/16"	5/32"	Material Certificate	1	91853A550	0000
	7/8"-9	1 5/16"	29/32"	5/32"	—	1	91853A037	00000
	1"-8	1 1/2"	1"	3/16"	Material Certificate	1	91853A038	00000
	1 1/4"-7	1 7/8"	1 1/4"	7/32"	Material Certificate	1	91853A040	00000
	1 1/2"-6	2 1/4"	1 1/2"	1/4"	Material Certificate	1	91853A041	00000