3/8"-12 Shafts | McMaster-Carr

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74 Products

Selecting Compatible Lead Screws and Nuts

Multiple thread channels (also known as thread starts) create faster linear travel than lead screws with a single thread start. Operating with less backlash (play) than Precision Acme Lead Screws and Nuts, these lead screws and nuts provide increased nut life and more reliable movement in automated systems. All components are corrosion resistant for use in harsh environments. To ensure compatibility, select components that have the same thread type, thread size, and number of thread starts.

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

For technical drawings and 3-D models, click on a part number.

Lead Screws—Right-Hand Threaded

303 Stainless Steel
Thread Size	Lg.	No. of Thread Starts	Thread Type	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Hardness	Tensile Strength, psi		Each
3/8"-12	6ft.	3	Rounded Acme	3:1	0.25"	±0.0006" per in.	Brinell 160	90,000	00000000	0000000

Flange Nuts—Right-Hand Threaded

Flange nuts with wear-compensating internal O-ring or wear-compensating spring maintain a tight fit even when their threads begin to wear. They resist backlash to maintain accuracy over time, which is important in applications such as 3D printing and robotics.

				Flange
	Thread Size	Lg.	Dia.	Dia.	Thick.	No. of Thread Starts	Thread Type	Speed Ratio	Travel Distance per Turn	Bolt Circle Dia.	Tensile Strength, psi	Dynamic Thrust Load Cap., lbs.		Each
Acetal Plastic
B	3/8"-12	1"	0.625"	1 7/64"	3/16"	3	Rounded Acme	3:1	0.25"	7/8"	9,700	75	00000000	000000
Acetal Plastic with Wear-Compensating Spring
C	3/8"-12	1 29/32"	0.703"	1 1/2"	3/16"	3	Rounded Acme	3:1	0.25"	1 1/8"	9,700	10	00000000	00000

Precision Acme Lead Screws and Nuts

Pair with a motor in automated motion and positioning applications. A tight thread fit allows these lead screws and nuts to make accurate, repeatable starts and stops. Also known as single-start and self-locking lead screws and nuts, they have a single thread that runs the length of the screw. The nut travels only when the screw turns, so your system won’t unexpectedly move when the lead screw is at rest. To ensure compatibility, please select components that have the same thread direction, thread size, and number of thread starts.

Carbon steel lead screws and flanges have good machinability. Black-oxide alloy steel lead screws are hard and strong. They have mild corrosion resistance and a dark surface color. 303 and 304 stainless steel lead screws and flanges have good corrosion resistance.

932 bearing bronze and 673 bronze nuts are wear resistant. They have good machinability and fair corrosion resistance. Cast iron nuts have good machinability and high strength. PET plastic nuts are lightweight and corrosion resistant.

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

For technical drawings and 3-D models, click on a part number.

Lead Screws—Right-Hand Threaded

Right-Hand Threads

1018 Carbon Steel
Thread Size	Lg.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Thread Fit	Hardness	Tensile Strength, psi		Each
3/8"-12	18"	1	1:1	0.083"	±0.009" per ft.	Class 2C	Not Rated	Not Rated	000000000	000000
3/8"-12	3 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Not Rated	Not Rated	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Not Rated	Not Rated	000000000	00000
Black-Oxide 4140 Alloy Steel
3/8"-12	18"	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 271	125,000	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 271	125,000	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 271	125,000	000000000	000000
304 Stainless Steel
3/8"-12	18"	1	1:1	0.083"	±0.009" per ft.	Class 2C	Not Rated	Not Rated	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 150	72,000	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 150	72,000	000000000	000000

Lead Screws—Left-Hand Threaded

Left-Hand Threads

Black-Oxide 4140 Alloy Steel
Thread Size	Lg.	Lg., ft.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Thread Fit	Hardness	Tensile Strength, psi		Each
3/8"-12	3 ft.	3	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 271	125,000	000000000	000000
3/8"-12	6 ft.	6	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 271	125,000	000000000	00000
304 Stainless Steel
3/8"-12	3 ft.	3	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 150	72,000	000000000	00000
3/8"-12	6 ft.	6	1	1:1	0.083"	±0.009" per ft.	Class 2C	Brinell 150	72,000	000000000	00000

Lead Screws—Right-Hand-and-Left-Hand Threaded

Right-Hand-and-Left-Hand Threads

Right-hand-and-left-hand threaded lead screws have right-hand threads on one end and left-hand threads on the other. Use them where you want to drive nuts in opposite directions at the same time, such as for widening and narrowing chutes on packing and assembly lines. Note: A short length of threading at the center of the lead screw is not usable.

			Usable Thread Lg.
Thread Size	Lg.	Lg., ft.	Right Hand	Left Hand	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Thread Fit	Hardness	Tensile Strength, psi		Each
Black-Oxide 4140 Alloy Steel
3/8"-12	3 ft.	3	17"	17"	1	1:1	0.083"	±0.0003" per in.	Class 2C	Brinell 200	95,000	000000000	0000000

Round Nuts—Right-Hand Threaded

Cast Iron
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.	Temperature Range, °F		Each
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Brinell 217	Not Rated	__	000000000	000000
932 Bearing Bronze
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Brinell 65	700	__	00000000	00000
PET Plastic
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Not Rated	350	15° to 175°	00000000	00000

Round Nuts—Left-Hand Threaded

Cast Iron
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.	Temperature Range, °F		Each
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Brinell 217	Not Rated	__	000000000	000000
932 Bearing Bronze
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Brinell 65	700	__	00000000	00000
PET Plastic
3/8"-12	3/4"	1.344"	1	1:1	0.083"	Class 2C	Not Rated	350	15° to 175°	00000000	00000

Externally Threaded Nuts—Right-Hand Threaded

Combine externally threaded nuts with a flange to create a custom flange nut.

						External Thread
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Size	Lg.	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.	Temperature Range, °F		Each
673 Bronze
3/8"-12	5/8"	0.688"	1	1:1	0.083"	9/16"-18	3/8"	Class 2C	Brinell 70	Not Rated	__	000000000	000000
PET Plastic
3/8"-12	5/8"	0.688"	1	1:1	0.083"	9/16"-18	3/8"	Class 2C	Not Rated	350	15° to 175°	000000000	00000

Externally Threaded Nuts—Left-Hand Threaded

Combine externally threaded nuts with a flange to create a custom flange nut.

						External Thread
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Size	Lg.	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.		Each
673 Bronze
3/8"-12	5/8"	0.688"	1	1:1	0.083"	9/16"-18	3/8"	Class 2C	Brinell 70	Not Rated	000000000	000000

Flanges

Thread onto an externally threaded acme nut to create a custom flange nut.

Carbon steel flanges have good machinability. However, they will rust when exposed to moisture. Black-oxide carbon steel flanges have mild corrosion resistance in dry environments and a dark surface color. 303 stainless steel flanges have good corrosion resistance.

Black-Oxide 1117 Carbon Steel
Flange Thread Size	Flange Dia.	Flange Thick.	Bolt Circle Dia.	Flange Hardness		Each
9/16"-18	1 39/64"	13/32"	1 1/8"	Brinell 135	00000000	000000
1215 Carbon Steel
9/16"-18	1 39/64"	13/32"	1 1/8"	Not Rated	000000000	00000
303 Stainless Steel
9/16"-18	1 39/64"	13/32"	1 1/8"	Brinell 140	0000000	00000

Fast-Travel Precision Acme Lead Screws and Nuts

Multiple thread channels (also known as thread starts) create faster linear travel than lead screws with a single thread start. The threads have a tight thread fit for accurate, repeatable starts and stops. Pair with a motor in automated motion and positioning applications. To ensure compatibility, please select components that have the same thread direction, thread size, and number of thread starts.

Carbon steel lead screws and flanges have good machinability. 303 and 304 stainless steel lead screws and flanges have good corrosion resistance.

932 bearing bronze and 673 bronze nuts are wear resistant. They have good machinability and fair corrosion resistance.

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

For technical drawings and 3-D models, click on a part number.

Lead Screws—Right-Hand Threaded

1018 Carbon Steel
Thread Size	Lg.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Thread Fit	Hardness	Tensile Strength, psi		Each
3/8"-12	18"	2	2:1	0.167"	±0.009" per ft.	Class 2C	Not Rated	Not Rated	000000000	000000
3/8"-12	3 ft.	2	2:1	0.167"	±0.009" per ft.	Class 2C	Brinell 126	64,000	000000000	00000
3/8"-12	6 ft.	2	2:1	0.167"	±0.009" per ft.	Class 2C	Brinell 126	64,000	000000000	00000

Lead Screws—Left-Hand Threaded

1018 Carbon Steel
Thread Size	Lg., ft.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Accuracy for Travel Distance per Turn	Thread Fit	Hardness	Tensile Strength, psi		Each
3/8"-12	3	2	2:1	0.167"	±0.009" per ft.	Class 2C	Brinell 126	64,000	000000000	000000
3/8"-12	6	2	2:1	0.167"	±0.009" per ft.	Class 2C	Brinell 126	64,000	000000000	00000

Externally Threaded Nuts—Right-Hand Threaded

Combine externally threaded nuts with a flange to create a custom flange nut.

						External Thread
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Size	Lg.	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.		Each
673 Bronze
3/8"-12	5/8"	0.688"	2	2:1	0.167"	9/16"-18	3/8"	Class 2C	Brinell 70	Not Rated	000000000	000000

Externally Threaded Nuts—Left-Hand Threaded

Combine externally threaded nuts with a flange to create a custom flange nut.

						External Thread
Thread Size	Lg.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Size	Lg.	Thread Fit	Hardness	Dynamic Thrust Load Cap., lbs.		Each
673 Bronze
3/8"-12	5/8"	0.688"	2	2:1	0.167"	9/16"-18	3/8"	Class 2C	Brinell 70	Not Rated	000000000	000000

Flanges

Thread onto an externally threaded acme nut to create a custom flange nut.

1215 Carbon Steel
Flange Thread Size	Flange Dia.	Flange Thick.	Bolt Circle Dia.	Flange Hardness		Each
9/16"-18	1 39/64"	13/32"	1 1/8"	Not Rated	000000000	000000
303 Stainless Steel
9/16"-18	1 39/64"	13/32"	1 1/8"	Brinell 140	0000000	00000

Acme 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, thread size, and number of thread starts.

Carbon steel components are easier to machine than alloy steel components. Zinc-plated carbon steel components have mild corrosion resistance. Alloy steel components are harder and stronger than carbon steel components. Cast iron components have good machinability and high strength. 360 brass components have excellent machinability and good corrosion resistance. 932 bearing bronze components are more wear resistant than brass components. They have good machinability and fair corrosion resistance. 18-8 stainless steel components have good corrosion resistance. 316 stainless steel components have excellent corrosion resistance.

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

For technical drawings and 3-D models, click on a part number.

Lead Screws—Right-Hand Threaded

Carbon Steel
Thread Size	Lg.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Fastener Strength Grade/Class	Hardness	Tensile Strength, psi	Specifications Met		Each
3/8"-12	12"	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	64,000	ASTM A108	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	64,000	ASTM A108	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	53,000	ASTM A108	000000000	00000
3/8"-12	12 ft.	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	64,000	ASTM A108	000000000	00000
Alloy Steel
3/8"-12	6"	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	00000
3/8"-12	12"	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	00000
3/8"-12	2 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	000000
3/8"-12	12 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	000000
18-8 Stainless Steel
3/8"-12	12"	1	1:1	0.083"	Class 2G	__	Rockwell B96	Not Rated	__	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	__	Rockwell B96	Not Rated	__	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	__	Rockwell B96	Not Rated	__	000000000	000000
3/8"-12	12 ft.	1	1:1	0.083"	Class 2G	__	Rockwell B96	Not Rated	__	000000000	000000
316 Stainless Steel
3/8"-12	12"	1	1:1	0.083"	Class 2G	ASTM Grade B8M	Rockwell B97	75,000	ASTM A193	000000000	00000
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B8M	Rockwell B97	75,000	ASTM A193	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B8M	Rockwell B97	75,000	ASTM A193	000000000	000000

Lead Screws—Left-Hand Threaded

Carbon Steel
Thread Size	Lg.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Fastener Strength Grade/Class	Hardness	Tensile Strength, psi	Specifications Met		Each
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	53,000	ASTM A108	000000000	000000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B61	53,000	ASTM A108	000000000	00000
Alloy Steel
3/8"-12	3 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	00000
3/8"-12	6 ft.	1	1:1	0.083"	Class 2G	ASTM Grade B7	Rockwell C35	125,000	ASTM A193	000000000	000000

Hex-Head Screws—Right-Hand Threaded

Hex head screws fasten heavy loads. They’re generally shorter than lead screws and can be tightened with a wrench. Length is measured from under the head.

						Head
Thread Size	Lg.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Lg.	Wd.	Ht.	Thread Fit	Fastener Strength Grade/Class	Hardness	Tensile Strength, psi		Each
Carbon Steel
3/8"-12	3"	1	1:1	0.083"	2 1/2" to 3"	9/16"	15/64"	Class 2G	Grade 5	Rockwell C19	105,000	000000000	000000
3/8"-12	4"	1	1:1	0.083"	3 1/2" to 4"	9/16"	15/64"	Class 2G	Grade 5	Rockwell C19	105,000	000000000	00000
3/8"-12	6"	1	1:1	0.083"	5 1/2" to 6"	9/16"	15/64"	Class 2G	Grade 5	Rockwell C19	105,000	000000000	00000

Coupling Nuts—Right-Hand Threaded

Coupling nuts connect two lead screws.

Carbon Steel
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness		Each
3/8"-12	1 7/8"	1/2"	1	1:1	0.083"	Class 2G	Rockwell B75	000000000	000000

Flange Nuts—Right-Hand Threaded

Flange nuts move objects along the length of a lead screw. Flange nuts have a wide machinable flange for custom mounting.

			Flange
Thread Size	Ht.	Dia.	Dia.	Thick.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness		Each
932 Bearing Bronze
3/8"-12	7/8"	1/2"	1"	1/8"	1	1:1	0.083"	Class 2G	Not Rated	000000000	0000000

Round Nuts—Right-Hand Threaded

Round nuts move objects along the length of a lead screw.

360 Brass
Thread Size	Ht.	Dia.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Specifications Met		Each
3/8"-12	3/8"	3/4"	1	1:1	0.083"	Class 2G	Rockwell B55	ASTM B16	000000000	00000
932 Bearing Bronze
3/8"-12	3/4"	7/8"	1	1:1	0.083"	Class 2G	Not Rated	ASTM B505	000000000	00000

Hex Nuts—Right-Hand Threaded

Hex nuts fasten and position lead screw components.

Carbon Steel
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Specifications Met		Each
3/8"-12	23/64"	11/16"	1	1:1	0.083"	Class 2G	Rockwell B75	__	000000000	00000
Zinc-Plated Carbon Steel
3/8"-12	23/64"	11/16"	1	1:1	0.083"	Class 2G	Rockwell B75	__	000000000	00000
360 Brass
3/8"-12	3/8"	3/4"	1	1:1	0.083"	Class 2G	Rockwell B75	ASTM B16	000000000	0000
18-8 Stainless Steel
3/8"-12	23/64"	11/16"	1	1:1	0.083"	Class 2G	Not Rated	__	000000000	00000

Hex Nuts—Left-Hand Threaded

Hex nuts fasten and position lead screw components.

Carbon Steel
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Fastener Strength Grade/Class	Hardness		Each
3/8"-12	23/64"	11/16"	1	1:1	0.083"	Class 2G	Grade 2	Rockwell B85	000000000	00000
18-8 Stainless Steel
3/8"-12	23/64"	11/16"	1	1:1	0.083"	Class 2G	__	Not Rated	000000000	00000

Square Nuts—Right-Hand Threaded

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
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Specifications Met		Each
3/8"-12	3/8"	3/4"	1	1:1	0.083"	Class 2G	Rockwell B55	ASTM B16	000000000	00000

Square Nuts—Left-Hand Threaded

360 Brass
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness	Specifications Met		Each
3/8"-12	3/8"	3/4"	1	1:1	0.083"	Class 2G	Rockwell B55	ASTM B16	000000000	00000

Flat Handles—Right-Hand Threaded

Handles fasten and position lead screw components. Handles are easy to grip and tighten by hand for quick assembly and disassembly.

Cast Iron
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness		Each
3/8"-12	1 1/8"	9 1/2"	1	1:1	0.083"	Class 2G	Rockwell B72	000000000	000000

Offset Handles—Right-Hand Threaded

Handles fasten and position lead screw components. Handles are easy to grip and tighten by hand for quick assembly and disassembly.

Cast Iron
Thread Size	Ht.	Wd.	No. of Thread Starts	Speed Ratio	Travel Distance per Turn	Thread Fit	Hardness		Each
3/8"-12	1 3/4"	4 1/4"	1	1:1	0.083"	Class 2G	Rockwell B67	000000000	000000

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Selecting Compatible Lead Screws and Nuts

Fast-Travel Ultra-Precision Lead Screws and Nuts

Precision Acme Lead Screws and Nuts

Fast-Travel Precision Acme Lead Screws and Nuts

Acme Lead Screws and Nuts