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When a motion-control project demands consistent torque transfer and dimensional accuracy, undersized or poorly machined gears become the weak link. Engineers, CNC builders, and robotics makers who need a dependable 1.5 module straight spur gear will find this 45# steel option covers the most common shaft and tooth-count combinations in a single listing.
Each gear is machined from 45# medium-carbon steel, offering a balance of hardness and machinability suited to moderate-to-high load applications. The module is 1.5 (pitch = 4.712 mm), tooth counts range from 12 T to 27 T, and bore diameters span 6 mm to 18 mm (approximately 0.24 in to 0.71 in). Select keyway (KWY) variants include a pre-cut keyway slot (4 mm or 5 mm or 6 mm width) for positive shaft locking without set-screw slippage.
Typical use cases include DC motor output stages in CNC router Z-axis drives, gear-reduction stages in robotic arm joints requiring a 1.5 mod spur gear for torque multiplication, and replacement transmission gears in small industrial automation equipment where standard metric module gearing is specified.
Machined from 45# steel for a tensile strength typically in the 600–800 MPa range, providing durability under cyclic loading in motor transmission and drive applications.
Covers 12 T through 27 T in a single listing, letting you select the exact gear ratio stage you need without sourcing from multiple suppliers.
Bore options from 6 mm to 18 mm (≈ 0.24–0.71 in) accommodate common motor shaft diameters used in NEMA 17/23 steppers, DC gearmotors, and servo output shafts.
KWY variants include a machined keyway slot (4 mm, 5 mm, or 6 mm width depending on bore) for positive rotational locking — eliminating set-screw-only retention on high-torque shafts.
Available in packs of 1 or 4, making it straightforward to stock spares or build multi-stage gear trains without placing separate orders.
Standard straight spur tooth geometry transmits power efficiently along parallel shafts and produces no axial thrust load, simplifying bearing selection in compact drive assemblies.
| Module (Mod) | 1.5 |
|---|---|
| Tooth Count | 12 T – 27 T (see variant options) |
| Bore Diameter | 6 mm – 18 mm (see variant options) |
| Pitch Diameter | 18 mm – 40.5 mm (Mod × Teeth) |
| Pressure Angle | 20° (standard) |
| Material | 45# Medium-Carbon Steel |
| Surface Finish | See variant options |
| Keyway | Available on select variants (4 mm / 5 mm / 6 mm width) |
| Gear Type | Straight Spur Gear |
| Tooth Profile | Involute |
| Hub Width | See variant options |
| Pack Quantity | 1 or 4 (see variant options) |
The tooth count determines the gear ratio when paired with a mating gear. Divide the driven gear teeth by the driving gear teeth to get the ratio. For example, pairing a 12 T drive gear with a 24 T driven gear gives a 2:1 reduction. Select the combination that achieves your target RPM or torque output.
Measure your motor shaft diameter with a caliper. Choose the bore that matches exactly — a bore that is too large will cause runout and vibration. Common stepper motor shafts are 5 mm, 6.35 mm, or 8 mm; DC gearmotor output shafts are often 6 mm, 8 mm, or 10 mm. If your shaft is between listed sizes, consider a keyway variant with the next bore up and use a key for positive locking.
For low-torque or intermittent-duty applications, a set screw on a standard bore is often sufficient. For continuous high-torque loads or reversing drives, a keyway variant provides positive rotational locking and prevents the gear from spinning on the shaft under shock loads. If your application involves frequent direction changes or high peak torque, choose a KWY variant.
45# medium-carbon steel is not inherently corrosion-resistant. In dry indoor environments (CNC machines, robotics enclosures) surface oxidation is minimal. For humid or outdoor environments, apply a light machine oil or grease coating to the gear teeth and bore. If corrosion resistance is a primary requirement, consider stainless steel or nylon gear alternatives.
Yes. Any gear or rack manufactured to the Mod 1.5 standard with a 20° pressure angle will mesh correctly with these gears. This includes Mod 1.5 racks used in CNC router linear drives and Mod 1.5 pinion gears used in rotary stages.
Load capacity depends on tooth count, face width, operating speed, and lubrication. As a conservative guideline, Mod 1.5 steel spur gears in this size range are suitable for transmitted tangential loads of approximately 50–300 N depending on tooth count and RPM. For precise load calculations, apply AGMA or ISO 6336 gear rating standards using the actual face width of your selected variant.
If you are prototyping or replacing a single failed gear, the single-piece option is the most cost-effective. If you are building a multi-stage gear train, stocking spares for a production machine, or running a small batch of assemblies, the 4-pack offers a lower per-unit cost and reduces reorder frequency.
