Screw Gears | McMaster-Carr

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Gear

Shaft-Mounted Worm

Worm

System of Measurement

Shaft Diameter

Gear Module

Gear Pitch Diameter

Number of Teeth

Gear Type

Speed Ratio

Pressure Angle

Material

Bore Type

Number of Thread Starts

Face Width

Thread Direction

Gear Pitch

Hub Diameter

Worm Length

Overall Width

Hub Width

Tooth Direction

RoHS

Compliant with Exemptions

REACH

Compliant

Not Compliant

Export Control Classification Number (ECCN)

EAR99

U.S.–Mexico–Canada Agreement (USMCA) Qualifying

Yes

DFARS Specialty Metals

Exempt

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128 Products

About Gears

Compare gear types, measure pitch and module, calculate mounting distance, increase speed or torque, and more.

Metal Worms and Worm Gears

Worm and

Gear Sold

Separately

Worm gears use screw threads to make large reductions to shaft speed while transmitting motion at a right angle. They transmit motion from worm to gear and cannot be reversed. For gears and worms to mesh correctly, they must have the same pressure angle, pitch/module, number of thread starts, and thread direction. These worms are compatible with plastic worm gears.

Worms


Keyed Bore	Round Bore

303 Stainless Steel—303 stainless steel worms won’t rust in wet environments, so they’re commonly used in food-processing plants and other areas with frequent cleaning.

Black-Oxide 1045 Carbon Steel—Black-Oxide 1045 carbon steel worms have rolled threads.

Hardened—Hardened 1045 carbon steel worms have ground threads, which are more durable and precise than rolled threads.

									Keyway		Hub
	Gear Module	Gear Pitch	Pressure Angle	Worm Lg.	Gear Pitch Dia.	OD	For Shaft Dia.	No. of Thread Starts	Wd.	Dp.	Dia., mm	Material	Thread Direction	Tooth Heat Treatment	Tooth Mechanical Finish	Set Screw Included		Each
Keyed Bore—1144 Carbon Steel



		—	12	14 1/2°	1 1/8"	1"	1.17"	1/2"	1	0.125"	0.063"	—	—	Right Hand	Not Hardened	Unfinished	—	57545K527	000000


		—	10	14 1/2°	1 3/8"	1 1/4"	1.45"	5/8"	1	0.188"	0.094"	—	—	Right Hand	Not Hardened	Unfinished	—	57545K427	00000
		—	8	14 1/2°	1 3/4"	1 1/2"	1.75"	3/4"	1	0.188"	0.094"	—	—	Right Hand	Not Hardened	Unfinished	—	57545K327	000000
		—	6	14 1/2°	2 1/2"	2"	2.33"	7/8"	1	0.188"	0.094"	—	—	Right Hand	Not Hardened	Unfinished	—	57545K227	000000


		Round Bore—Black-Oxide 1045 Carbon Steel



				0.5	—	20°	18 mm	11 mm	12 mm	5 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K624	00000


				0.5	—	20°	18 mm	11 mm	12 mm	5 mm	2	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K625	00000
				0.8	—	20°	30 mm	14 mm	15.6 mm	6 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K626	00000
				0.8	—	20°	30 mm	14 mm	15.6 mm	6 mm	2	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K627	00000
				1	—	20°	32 mm	16 mm	18 mm	6 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K633	00000
				1	—	20°	32 mm	16 mm	18 mm	6 mm	2	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K634	00000
				1	—	20°	32 mm	16 mm	18 mm	8 mm	1	—	—	—	—	Right Hand	Hardened	Ground	Yes	57545K646	00000
				1.25	—	20°	37 mm	21 mm	23.5 mm	8 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K628	00000
				1.5	—	20°	40 mm	25 mm	28 mm	8 mm	1	—	—	20	1045 Carbon Steel	Right Hand	Not Hardened	Unfinished	No	57545K631	00000
				1.5	—	20°	40 mm	25 mm	28 mm	8 mm	2	—	—	20	1045 Carbon Steel	Right Hand	Not Hardened	Unfinished	No	57545K632	00000
				1.5	—	20°	40 mm	25 mm	28 mm	10 mm	1	—	—	20	1045 Carbon Steel	Right Hand	Hardened	Ground	No	57545K644	00000


				2	—	14 1/2°	46 mm	31 mm	35 mm	12 mm	1	—	—	25	1045 Carbon Steel	Left Hand	Not Hardened	Unfinished	No	57545K639	00000
				2	—	14 1/2°	46 mm	31 mm	35 mm	12 mm	1	—	—	25	1045 Carbon Steel	Right Hand	Not Hardened	Unfinished	No	57545K642	00000
				2	—	14 1/2°	46 mm	31 mm	35 mm	12 mm	2	—	—	25	1045 Carbon Steel	Right Hand	Not Hardened	Unfinished	No	57545K643	00000
				2.5	—	20°	63 mm	37 mm	42 mm	15 mm	2	—	—	30	1045 Carbon Steel	Right Hand	Not Hardened	Unfinished	No	57545K638	00000


				Round Bore—303 Stainless Steel



						0.5	—	20°	18 mm	11 mm	12 mm	5 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K653	00000


						0.5	—	20°	18 mm	11 mm	12 mm	5 mm	2	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K654	00000
						0.8	—	20°	30 mm	14 mm	15.6 mm	6 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K655	00000
						1	—	20°	32 mm	16 mm	18 mm	6 mm	1	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K659	00000
						1	—	20°	32 mm	16 mm	18 mm	6 mm	2	—	—	—	—	Right Hand	Not Hardened	Unfinished	Yes	57545K661	00000
						1.5	—	20°	40 mm	25 mm	28 mm	8 mm	2	—	—	20	303 Stainless Steel	Right Hand	Not Hardened	Unfinished	No	57545K658	00000

Shaft-Mounted Worms

4140 Alloy Steel—4140 alloy steel worms are already mounted on a shaft, so they’re ready to use with no machining required. The threads are ground into the shaft for higher precision than rolled threads, and hardened for additional durability and precision.

						Shaft, mm
	Gear Module	Pressure Angle	Worm Lg., mm	Gear Pitch Dia., mm	OD, mm	Dia.	Lg.	No. of Thread Starts	Thread Direction	Tooth Heat Treatment	Tooth Mechanical Finish		Each
4140 Alloy Steel



		0.5	20°	12	9	10	6	65	1	Right Hand	Hardened	Ground	57545K611	000000


		0.5	20°	12	9	10	6	65	2	Right Hand	Hardened	Ground	57545K612	00000
		0.8	20°	20	12	14	8	85	1	Right Hand	Hardened	Ground	57545K613	00000
		0.8	20°	20	12	14	8	85	2	Right Hand	Hardened	Ground	57545K614	00000
		1	20°	30	16	18	18	140	1	Right Hand	Hardened	Ground	57545K617	000000
		1.5	20°	40	25	28	26	190	1	Right Hand	Hardened	Ground	57545K615	000000

Gears

Bronze—Bronze gears have low friction and dissipate heat better than cast iron gears to provide a long service life for both the gear and the worm. They’re also more corrosion resistant than cast iron gears.

Cast Iron—Cast iron gears are strong and durable.

Speed Ratio—Speed ratio is the ratio by which output shaft speed is reduced. As speed decreases, torque increases.

												Hub
	Gear Module	Gear Pitch	Speed Ratio	No. of Teeth	Pressure Angle	Gear Pitch Dia.	For No. of Thread Starts	OD	Face Wd.	Overall Wd.	For Shaft Dia.	Dia.	Wd.	Material	For Thread Direction	Tooth Heat Treatment	Tooth Mechanical Finish		Each
Round Bore—Cast Iron



		—	12	18:1	18	14 1/2°	1 1/2"	1	1.69"	1/2"	1.125"	1/2"	1.25"	0.625"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K511	0000000


		—	12	20:1	20	14 1/2°	1.67"	1	1.85"	1/2"	1.125"	1/2"	1.25"	0.625"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K513	000000
		—	12	30:1	30	14 1/2°	2 1/2"	1	2.69"	1/2"	1.125"	1/2"	1.25"	0.625"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K515	000000
		—	12	40:1	40	14 1/2°	3.33"	1	3.52"	1/2"	1.25"	5/8"	1.5"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K517	000000
		—	12	60:1	60	14 1/2°	5"	1	5.19"	1/2"	1.25"	5/8"	1.75"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K522	000000
		—	10	20:1	20	14 1/2°	2"	1	2.22"	5/8"	1.375"	1/2"	1.25"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K411	000000
		—	10	30:1	30	14 1/2°	3"	1	3.22"	5/8"	1.375"	5/8"	1.75"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K413	000000
		—	10	40:1	40	14 1/2°	4"	1	4.22"	5/8"	1.375"	5/8"	1.75"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K415	000000
		—	10	50:1	50	14 1/2°	5"	1	5.22"	5/8"	1.375"	3/4"	2"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K417	000000
		—	10	100:1	100	14 1/2°	10"	1	10.22"	5/8"	1.375"	3/4"	2.5"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K424	000000
		—	8	20:1	20	14 1/2°	2 1/2"	1	2.78"	3/4"	1.5"	3/4"	1.75"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K311	000000


		—	8	30:1	30	14 1/2°	3 3/4"	1	4.03"	3/4"	1.5"	3/4"	1.75"	0.75"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K313	000000
		—	8	40:1	40	14 1/2°	5"	1	5.28"	3/4"	1.625"	1"	2.375"	0.875"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K315	000000
		—	6	20:1	20	14 1/2°	3.33"	1	3.71"	1"	1.875"	3/4"	1.875"	0.875"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K211	000000
		—	6	24:1	24	14 1/2°	4"	1	4.37"	1"	1.875"	3/4"	1.875"	0.875"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K213	000000
		—	6	30:1	30	14 1/2°	5"	1	5.37"	1"	1.875"	7/8"	2.25"	0.875"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K215	000000
		—	6	40:1	40	14 1/2°	6.67"	1	7.04"	1"	1.875"	1"	2.5"	0.875"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K217	000000
		—	6	72:1	72	14 1/2°	12"	1	12.37"	1"	2.25"	1 1/4"	3"	1.25"	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K244	000000
		1	—	60:1	60	20°	60 mm	1	63 mm	10 mm	20 mm	10 mm	30 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K787	00000
		1	—	80:1	80	20°	80 mm	1	83 mm	10 mm	20 mm	10 mm	35 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K788	00000
		1	—	100:1	100	20°	100 mm	1	103 mm	10 mm	20 mm	10 mm	40 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K785	00000


		1	—	120:1	120	20°	120 mm	1	123 mm	10 mm	20 mm	10 mm	40 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K786	00000
		1.5	—	30:1	30	20°	45 mm	1	49.5 mm	12 mm	22 mm	10 mm	30 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K779	00000
		1.5	—	40:1	40	20°	60 mm	1	64.5 mm	12 mm	22 mm	12 mm	30 mm	10 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K781	00000
		2	—	10:1	20	14 1/2°	40 mm	2	46 mm	22 mm	35 mm	12 mm	33 mm	13 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K821	00000
		2	—	20:1	20	14 1/2°	40 mm	1	46 mm	22 mm	35 mm	12 mm	33 mm	13 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K819	00000
		2.5	—	10:1	20	20°	50 mm	2	57.5 mm	22 mm	36 mm	12 mm	35 mm	14 mm	Cast Iron	Right Hand	Not Hardened	Unfinished	57545K793	00000


		Round Bore—Bronze



				—	12	20:1	20	14 1/2°	1.67"	1	1.87"	1/2"	1"	1/2"	1.25"	0.5"	Bronze	Right Hand	Not Hardened	Unfinished	57545K231	000000


				—	12	30:1	30	14 1/2°	2 1/2"	1	2.7"	1/2"	1.12"	1/2"	1.19"	0.62"	Bronze	Right Hand	Not Hardened	Unfinished	57545K232	000000
				—	12	40:1	40	14 1/2°	3.33"	1	3.54"	1/2"	1.12"	5/8"	1.44"	0.62"	Bronze	Right Hand	Not Hardened	Unfinished	57545K233	000000
				—	10	20:1	20	14 1/2°	2"	1	2.24"	5/8"	1.245"	1/2"	1.25"	0.62"	Bronze	Right Hand	Not Hardened	Unfinished	57545K234	000000
				—	10	30:1	30	14 1/2°	3"	1	3.24"	5/8"	1.245"	5/8"	1.69"	0.62"	Bronze	Right Hand	Not Hardened	Unfinished	57545K235	000000
				—	10	40:1	40	14 1/2°	4"	1	4.24"	5/8"	1.245"	5/8"	1.69"	0.62"	Bronze	Right Hand	Not Hardened	Unfinished	57545K236	000000
				—	10	50:1	50	14 1/2°	5"	1	5.24"	5/8"	1.375"	3/4"	1.94"	0.75"	Bronze	Right Hand	Not Hardened	Unfinished	57545K237	000000
				0.5	—	10:1	20	20°	10 mm	2	11 mm	5 mm	12 mm	4 mm	9 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K735	00000
				0.5	—	15:1	30	20°	15 mm	2	16 mm	5 mm	12 mm	4 mm	12 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K737	00000
				0.5	—	20:1	20	20°	10 mm	1	11 mm	5 mm	12 mm	4 mm	9 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K734	00000
				0.5	—	30:1	30	20°	15 mm	1	16 mm	5 mm	12 mm	4 mm	12 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K736	00000


				0.5	—	40:1	40	20°	20 mm	1	21 mm	5 mm	12 mm	5 mm	15 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K738	00000
				0.5	—	50:1	50	20°	25 mm	1	26 mm	5 mm	12 mm	5 mm	20 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K739	00000
				0.5	—	60:1	60	20°	30 mm	1	31 mm	5 mm	12 mm	5 mm	25 mm	7 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K741	00000
				0.8	—	10:1	20	20°	16 mm	2	17.6 mm	9 mm	18 mm	5 mm	12 mm	9 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K743	00000
				0.8	—	20:1	20	20°	16 mm	1	17.6 mm	9 mm	18 mm	5 mm	12 mm	9 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K742	00000
				0.8	—	30:1	30	20°	24 mm	1	25.6 mm	9 mm	18 mm	5 mm	18 mm	9 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K744	00000
				0.8	—	40:1	40	20°	32 mm	1	33.6 mm	9 mm	18 mm	6 mm	20 mm	9 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K746	00000
1				—	10:1	20	20°	20 mm	2	23 mm	10 mm	20 mm	6 mm	16 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K764	00000
1	—			30:1	30	20°	30 mm	1	33 mm	10 mm	20 mm	6 mm	20 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K765	00000
1.25	—			20:1	20	20°	25 mm	1	28.75 mm	10 mm	20 mm	6 mm	20 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K749	00000


1.5	—			10:1	20	20°	30 mm	2	34.5 mm	12 mm	22 mm	8 mm	22 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K757	00000
1.5	—			15:1	30	20°	45 mm	2	49.5 mm	12 mm	22 mm	10 mm	30 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K759	00000
1.5	—			20:1	20	20°	30 mm	1	34.5 mm	12 mm	22 mm	8 mm	22 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K756	00000
1.5	—			30:1	30	20°	45 mm	1	49.5 mm	12 mm	22 mm	10 mm	30 mm	10 mm	Bronze	Right Hand	Not Hardened	Unfinished	57545K758	00000

High-Power Metal Helical Gears

The helical teeth on these gears stay in contact longer than straight teeth, which allows them to transmit higher loads at higher speeds than spur gears.

Crossed Gears

Crossed helical gears, also known as screw gears, can be configured to transmit motion at a 90° angle or in a straight line. To transmit motion at a 90° angle, pair two gears with the same tooth direction. To transmit motion in a straight line, make sure to get one left-hand and one right-hand gear.

For gears to mesh correctly, they must have the same pressure angle and pitch/module. To change speed and torque in your assembly, pair two gears with different numbers of teeth.

								Hub				Keyway				Left-Hand Teeth		Right-Hand Teeth
	Gear Pitch	Gear Module	No. of Teeth	Helix Angle	Gear Pitch Dia.	OD	Face Wd.	Dia.	Wd.	Bore Type	For Shaft Dia.	Wd.	Dp.	Material	Tooth Heat Treatment		Each		Each
20° Pressure Angle



		—	1	13	45°	18.4 mm	20.38 mm	10 mm	15 mm	10 mm	Round Bore	6 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N289	000000	3598N291	000000


		—	1	26	45°	36.8 mm	38.77 mm	10 mm	30 mm	10 mm	Round Bore	10 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N296	00000	3598N297	00000
		—	1	30	45°	42.4 mm	44.43 mm	10 mm	35 mm	10 mm	Round Bore	10 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N298	00000	3598N299	00000
		—	1.5	10	45°	21.2 mm	24.21 mm	15 mm	16 mm	10 mm	Round Bore	8 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N276	00000	3598N277	00000
		—	1.5	13	45°	27.6 mm	30.58 mm	15 mm	23 mm	10 mm	Round Bore	10 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N278	00000	3598N279	00000
		—	1.5	26	45°	55.2 mm	58.15 mm	15 mm	40 mm	10 mm	Round Bore	12 mm	—	—	Black-Oxide 1045 Carbon Steel	Not Hardened	3598N285	00000	3598N286	00000


		14 1/2° Pressure Angle



				16	—	16	45°	1"	1.09"	1/2"	0.86"	0.5"	Keyed Bore with Set Screw	1/2"	0.125"	0.062"	1137 Carbon Steel	Hardened	2585N11	00000	2585N12	00000


				16	—	24	45°	1 1/2"	1.59"	1/2"	1.37"	0.5"	Keyed Bore with Set Screw	5/8"	0.187"	0.094"	1137 Carbon Steel	Hardened	2585N13	000000	2585N14	000000
				16	—	32	45°	2"	2.09"	1/2"	1.87"	0.5"	Keyed Bore with Set Screw	5/8"	0.187"	0.094"	1137 Carbon Steel	Hardened	2585N15	000000	2585N16	000000
				16	—	48	45°	3"	3.09"	1/2"	2.5"	0.5"	Keyed Bore with Set Screw	5/8"	0.187"	0.094"	1137 Carbon Steel	Hardened	2585N17	000000	2585N18	000000
				12	—	18	45°	1 1/2"	1.62"	3/4"	1.34"	0.5"	Keyed Bore with Set Screw	5/8"	0.187"	0.094"	1137 Carbon Steel	Hardened	2585N22	000000	2585N23	000000

Parallel Gears

Pair two parallel gears to transmit motion in a straight line or a gear with a rack to convert rotary motion to linear motion. Make sure mating components have different tooth directions.

For gears to mesh correctly, they must have the same pressure angle and pitch/module. To change speed and torque in your assembly, pair two gears with different numbers of teeth.

							Hub, mm						Left-Hand Teeth		Right-Hand Teeth
	Gear Module	No. of Teeth	Helix Angle	Gear Pitch Dia., mm	OD, mm	Face Wd., mm	Dia.	Wd.	Bore Type	For Shaft Dia., mm	Material	Tooth Heat Treatment		Each		Each
20° Pressure Angle



		1	20	21 1/2°	20	22	8	17	10	Round Bore	6	4140 Alloy Steel	Hardened	3598N159	000000	3598N161	000000


		1	30	21 1/2°	30	32	8	25	10	Round Bore	10	4140 Alloy Steel	Hardened	3598N171	000000	3598N172	000000
		1	44	21 1/2°	44	46	8	30	10	Round Bore	10	4140 Alloy Steel	Hardened	3598N182	000000	3598N183	000000

Parallel Gear Racks


Parallel Gear on Gear Rack (Sold Separately)

Pair these racks with parallel helical gears that have an opposite tooth direction to convert rotary motion to linear motion.

									Left-Hand Teeth		Right-Hand Teeth
	Gear Module	Lg., mm	Helix Angle	Pitch Ht., mm	Ht., mm	Face Wd., mm	Material	Tooth Heat Treatment		Each		Each
20° Pressure Angle



		1	100	21 1/2°	14	15	8	4140 Alloy Steel	Not Hardened	3598N263	0000000	3598N264	0000000


		1	500	21 1/2°	14	15	8	4140 Alloy Steel	Not Hardened	3598N272	000000	3598N273	000000

Plastic Worm Gears

These plastic gears are lighter and quieter than metal gears—pair them with metal worms for lubrication-free operation. Worm gears use screw threads to make large reductions to shaft speed while transmitting motion at a right angle. They transmit motion from worm to gear and cannot be reversed. For gears and worms to mesh correctly, they must have the same pressure angle, pitch/module, number of thread starts, and thread direction.

Gears

Acetal—Acetal gears are lightweight, and resist corrosion and chemicals. They absorb less moisture than nylon gears, so they’re less prone to dimensional changes. They’re best suited for light duty applications, such as prototyping.

Nylon—Nylon gears are lightweight and stronger than acetal gears.

Speed Ratio—Speed ratio is the ratio by which output shaft speed is reduced. As speed decreases, torque increases.

													Hub, mm
	Gear Module	Speed Ratio	No. of Teeth	Pressure Angle	Gear Pitch Dia., mm	For No. of Thread Starts	OD, mm	Face Wd., mm	Overall Wd., mm	For Shaft Dia., mm	Fabrication	Color	Dia.	Wd.	For Thread Direction		Each
Round Bore—Acetal



		0.5	10:1	20	20°	10	2	11	5	12	4	Molded	White	9	7	Right Hand	4037N112	000000


		0.5	20:1	20	20°	10	1	11	5	12	4	Molded	White	9	7	Right Hand	4037N111	00000
		0.5	30:1	30	20°	15	1	16	5	12	4	Molded	White	12	7	Right Hand	4037N113	00000
		0.5	40:1	40	20°	20	1	21	5	12	5	Molded	White	15	7	Right Hand	4037N115	00000
		0.5	50:1	50	20°	25	1	26	5	12	5	Molded	White	20	7	Right Hand	4037N116	00000
		0.5	60:1	60	20°	30	1	31	5	12	5	Molded	White	25	7	Right Hand	4037N117	00000
		0.8	10:1	20	20°	16	2	17.6	9	18	5	Molded	White	12	9	Right Hand	4037N119	00000
		0.8	50:1	50	20°	40	1	41.6	9	18	8	Molded	White	25	9	Right Hand	4037N124	00000
		0.8	60:1	60	20°	48	1	49.6	9	18	8	Molded	White	25	9	Right Hand	4037N125	00000


		Round Bore—Nylon



				1	10:1	20	20°	20	2	23	10	20	6	Molded	Blue	16	10	Right Hand	4037N129	00000


				1	30:1	30	20°	30	1	33	10	20	6	Molded	Blue	20	10	Right Hand	4037N131	00000
				1	50:1	50	20°	50	1	53	10	20	8	Molded	Blue	30	10	Right Hand	4037N133	00000
				1.5	10:1	20	20°	30	2	34.5	12	22	8	Molded	Blue	22	10	Right Hand	4037N127	00000