Castle Nuts | McMaster-Carr

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98 Products

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.

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.	Specs. Met	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"	—	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"	—	10	97190A030	00000
		5/8"-18	15/16"	35/64"	SAE Grade 5	5/32"	—	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"	—	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"	—	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"	—	1	97190A230	00000
		M6 × 1 mm	10 mm	7.5 mm	Class 8	1.6 mm	DIN 935	5	93760A212	0000


		M8 × 1.25 mm	13 mm	9.5 mm	Class 8	2 mm	DIN 935	5	93760A222	0000
		M10 × 1.5 mm	17 mm	12 mm	Class 8	2.5 mm	DIN 935	5	93760A233	0000
		M12 × 1.5 mm	19 mm	15 mm	Class 8	3.2 mm	DIN 935	5	93760A126	0000
		M12 × 1.75 mm	19 mm	15 mm	Class 8	3.2 mm	DIN 935	5	93760A317	0000
		M14 × 1.5 mm	22 mm	16 mm	Class 8	3.2 mm	DIN 935	1	93760A127	0000
		M14 × 2 mm	22 mm	16 mm	Class 8	3.2 mm	DIN 935	1	93760A111	0000
		M16 × 1.5 mm	24 mm	19 mm	Class 8	4 mm	DIN 935	10	93760A128	00000
		M16 × 2 mm	24 mm	19 mm	Class 8	4 mm	DIN 935	5	93760A328	00000
		M18 × 2.5 mm	27 mm	21 mm	Class 8	4 mm	DIN 935	1	93760A112	0000
		M20 × 2.5 mm	30 mm	22 mm	Class 8	4 mm	DIN 935	5	93760A337	00000


		M24 × 2 mm	36 mm	27 mm	Class 8	5 mm	DIN 935	1	93760A129	00000
		M24 × 3 mm	36 mm	27 mm	Class 8	5 mm	DIN 935	1	93760A340	0000
		M27 × 3 mm	41 mm	30 mm	Class 8	5 mm	DIN 935	1	93760A113	00000
		M30 × 3.5 mm	46 mm	33 mm	Class 8	6.3 mm	DIN 935	1	93760A114	00000


		Steel



				M12 × 1.5 mm	19 mm	15 mm	Class 8	3.2 mm	DIN 935	10	93760A131	0000


				M14 × 1.5 mm	22 mm	16 mm	Class 8	3.2 mm	DIN 935	1	93760A132	0000
				M14 × 2 mm	22 mm	16 mm	Class 8	3.2 mm	DIN 935	1	93760A115	0000
				M16 × 1.5 mm	24 mm	19 mm	Class 8	4 mm	DIN 935	1	93760A133	0000
				M16 × 2 mm	24 mm	19 mm	Class 8	4 mm	DIN 935	1	93760A116	0000
				M18 × 2.5 mm	27 mm	21 mm	Class 8	4 mm	DIN 935	1	93760A117	0000
				M20 × 2.5 mm	30 mm	22 mm	Class 8	4 mm	DIN 935	1	93760A118	0000
				M24 × 3 mm	36 mm	27 mm	Class 8	5 mm	DIN 935	1	93760A119	0000
				M30 × 3.5 mm	46 mm	33 mm	Class 8	6.3 mm	DIN 935	1	93760A121	00000
				M36 × 3 mm	55 mm	38 mm	Class 8	6.3 mm	DIN 935	1	93760A134	00000
M36 × 4 mm				55 mm	38 mm	Class 8	6.3 mm	DIN 935	1	93760A122	00000


M42 × 4.5 mm	65 mm			46 mm	Class 8	8 mm	DIN 935	1	93760A123	00000
M48 × 5 mm	75 mm			50 mm	Class 8	8 mm	DIN 935	1	93760A124	00000
M56 × 5.5 mm	85 mm			57 mm	Class 8	8 mm	DIN 935	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.

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-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.	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"	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	0000
	1"-8	1 1/2"	55/64"	3/16"	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"	1	95030A390	00000
	1 3/4"-12	2 5/8"	1 1/2"	3/8"	1	95030A410	00000
	2"-4 1/2	3"	1 23/32"	3/8"	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.	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	0000
	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"	1	91853A033	0000
	1/2"-20	3/4"	9/16"	1/8"	1	91853A535	0000
	5/8"-11	15/16"	23/32"	5/32"	1	91853A035	0000
	5/8"-18	15/16"	23/32"	5/32"	1	91853A545	0000


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