M25 Fasteners | McMaster-Carr

With a nylon insert that grips your threaded shaft or spindle without damaging its threads, these locknuts—also called shaft nuts—hold bearings, bushings, gears, and pulleys prone to vibration tightly in place. They come as one piece, so you can easily clamp them onto your shaft or spindle. But, since they aren’t made entirely of metal, they don’t stand up to heat as well as all-metal locknuts. Slots in their sides mean you can tighten and loosen them with a spanner wrench or spanner socket. Their face is also chamfered to help keep the size and weight of your assembly at a minimum. All meet international standards for bearing locknut dimensions.

Zinc-Plated Carbon Steel—Zinc-plated carbon steel locknuts resist rusting from some moisture, but you shouldn’t use them with salt water or chemicals. They are strong and resist wear, though they don’t stand up to corrosion as well as 303 stainless steel locknuts.

Carbon Steel—All carbon steel locknuts are strong and resist wear, though they don’t stand up to corrosion as well as 303 stainless steel locknuts.

303 Stainless Steel—303 stainless steel locknuts resist corrosion better than carbon steel locknuts but aren’t as strong. They withstand washdowns and chemicals.

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.

	Locknuts												Sockets
	Thread						Carbon Steel		Zinc-Plated Carbon Steel		303 Stainless Steel
	Size	Spacing	OD, mm	Wd., mm	Insert Max. Temp., ° F	Specs. Met		Each		Each		Each		Each
Chamfered Face



		M25 × 1.5 mm	Extra Fine	38	10.5	210	—	———	0	3552N32	000000	———	0	———	0


		M25 × 1.5 mm	Extra Fine	38	11	160	ISO 2982-2	6343K37	000000	———	0	6343K69	000000	5510N151	0000000

Bearing Nuts

Carbon Steel

Chamfered 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.

Chamfered Face—Chamfered-face bearing nuts weigh less and produce less heat than stepped-face nuts.

ISO 2982— Some chamfered-face bearing nuts meet ISO 2982 (formerly DIN 981), an international standard for bearing locknut dimensions. Their sizes correspond to SKF KM series. Use them with DIN 5406 spring lock washers.

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







				Chamfered Face

				M25 × 1.5 mm	Extra Fine	38	7	DIN 981, ISO 2982	DIN 5406	3554N16	00000	90391A116	00000	5510N181	0000000

Conduit Locknuts

Secure threaded conduit fittings to knockouts. These locknuts keep fittings from shifting, so connections stay stable and wiring is protected inside electrical boxes or enclosures.

For Metal and Plastic Fittings

304 Stainless Steel—The choice for wet and outdoor environments.

Nickel-Plated Brass—The plating enhances the corrosion resistance of brass, adding a durable protective finish.

	Each
Metric Thread







	304 Stainless Steel

	M25	—	7513K136	000000




			Nickel-Plated Brass

			M25	EN 60204	9147T111	0000

For Plastic Fittings

Nylon—Lightweight and chemical resistant, these fittings won't corrode.


Metric Thread







	Nylon

	M25	7877N131	00000


	M25	7877N132	0000

Ball Screws and Nuts


	Ball Nuts Flange Nut Style C

Internal ball bearings provide smooth low-friction travel in applications that require high speeds, accurate positioning, and repeatable movement. Also known as single-start ball screws and nuts, they have a single thread that runs the length of the screw. They operate with more torque than fast-travel ball screws and nuts. To ensure compatibility, select components that have the same thread direction and size. Ball nuts are furnished with a tube to keep ball bearings in place. Do not remove the tube until you are ready to install the nuts onto the screws.

Ball Screws—Right-Hand Threaded

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

Root Diameter—Root diameter indicates the diameter the ball screw will be after machining away the threads.

	Lg., mm	No. of Thread Starts	Travel Distance per Turn, mm	Accuracy for Travel Distance per Turn	Root Dia., mm	Hardness	Tensile Strength, psi	Temp. Range, ° F		Each
Carbon Steel



	M25	500	1	5	±0.210 mm/300 mm	22.2	Rockwell C58	21,000	5 to 175	6624K65	0000000


	M25	1,000	1	5	±0.210 mm/300 mm	22.2	Rockwell C58	21,000	5 to 175	6624K11	000000
	M25	1,500	1	10	±0.210 mm/300 mm	20.2	Rockwell C58	21,000	5 to 175	6624K16	000000

Platform Ball Nuts—Right-Hand Threaded

Image of Product. Front orientation. Contains Annotated. Ball Screws and Nuts. Ball Screws and Nuts , Platform Nut, Ball Nuts.

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

	Lg., mm	Wd., mm	Ht., mm	Ctr. Ht., mm	No. of Thread Starts	Travel Distance per Turn, mm	Hardness	Dynamic Thrust Load Cap., lb.	Max. Backlash, mm	Temp. Range, ° F		Each
Alloy Steel



	M25	35	60	45	20	1	5	Rockwell C58	1,500	0.1	5 to 175	6624K33	0000000


	M25	94	60	55	23	1	10	Rockwell C58	7,000	0.1	5 to 175	6624K35	000000

Flange Ball Nuts—Right-Hand Threaded

Style C

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

					Flange, mm
	Style	Thread Size	Lg., mm	Dia., mm	Wd.	Ht.	Thk.	No. of Thread Starts	Travel Distance per Turn, mm	Hardness	Dynamic Thrust Load Cap., lb.	Max. Backlash, mm	Temp. Range, ° F		Each
Alloy Steel



		C	M25	40	43	67	50	10	1	5	Rockwell C58	1,500	0.1	5 to 175	6624K46	0000000


		C	M25	98	60	96	72	15	1	10	Rockwell C58	7,000	0.1	5 to 175	6624K48	000000

Fast-Travel Ball Screws and Nuts


	Ball Nuts, Externally Threaded Nut, Style A

Multiple thread channels (also known as thread starts) create faster linear travel than ball screws with a single thread start. Internal ball bearings provide smooth low-friction travel in applications that require high speeds, accurate positioning, and repeatable movement. To ensure compatibility, select components that have the same thread size and number of thread starts. Ball nuts are furnished with a tube to keep ball bearings in place. Do not remove the tube until you are ready to install the nuts onto the screws.

Externally Threaded Ball Nuts—Right-Hand Threaded

Image of Product. Front orientation. Contains Annotated. Ball Screws and Nuts. Fast-Travel Ball Screws and Nuts, Ball Nuts, Externally Threaded Nut, Style A.

Style A

Carbon Steel—Carbon steel ball screws and nuts are case hardened, so they resist wear better than standard carbon steel. However, they are less corrosion resistant than black-oxide alloy steel screws and nuts.

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

	Thread Size	Lg., mm	Dia., mm	No. of Thread Starts	Travel Distance per Turn, mm	External Thread Size	Hardness	Dynamic Thrust Load Cap., lb.	Max. Backlash, mm	Temp. Range, ° F		Each
Carbon Steel



	A	M12	50	30	1	10	M25	Rockwell C56	1,000	0.02	32 to 150	4566N301	0000000