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When your motor drive project demands repeatable torque transfer without backlash surprises, finding a correctly pitched flat spur gear in the right tooth count is the first obstacle. Hobbyists, robotics builders, and small-machine designers working with Module 4M (4 mm/tooth pitch) drive trains need gears that mesh cleanly and mount securely — this listing covers the full 10T-to-38T range so you can spec the exact reduction ratio your build requires.
Each Module 4M flat spur gear is machined from engineering-grade metal (typically steel or aluminum alloy, confirm via variant detail), featuring a standard 4M tooth profile. Bore diameter and keyway dimensions vary by tooth count; overall gear outer diameter scales from approximately 48 mm (≈1.89 in) at 10T up to approximately 160 mm (≈6.30 in) at 38T. A mounting screw is included with each unit for shaft retention.
Typical use cases include DC motor gearbox reduction stages for CNC router axis drives, servo-driven robotic arm joints requiring a specific gear ratio, and custom conveyor or actuator builds where a Module 4M spur gear pair delivers the target RPM-to-torque conversion. Long-tail applications: "4M spur gear 20 tooth motor mount", "module 4 flat gear transmission DIY robot", "4M gear with set screw shaft coupling".
Select from 29 tooth-count variants (10T through 38T) to dial in your exact gear ratio without sourcing from multiple suppliers.
Each gear ships with a set screw for positive shaft retention, reducing assembly steps and preventing axial slippage under load.
Conforms to the international Module 4 (4 mm/tooth) standard, ensuring direct mesh compatibility with any Mod 4 mating gear in your drive train.
Low-profile flat spur design keeps axial stack height minimal — ideal for space-constrained motor bays and compact gearbox housings.
Precision-cut tooth flanks deliver consistent pitch engagement, reducing vibration and audible noise in continuous-duty motor drive applications.
Suited for CNC machines, robotic joints, conveyor actuators, and custom DIY drive systems — anywhere a reliable Module 4M spur gear transmission is needed.
| Module (Pitch) | 4M (4 mm per tooth) |
|---|---|
| Tooth Count (T) | 10T – 38T (see variant options) |
| Outer Diameter | See variant options |
| Bore Diameter | See variant options |
| Gear Width (Face Width) | See variant options |
| Material | See variant options |
| Finish / Coating | See variant options |
| Pressure Angle | 20° (standard) |
| Mounting Hardware | Set screw included |
| Packing Quantity | 1 pc per order (default) |
| Weight | See variant options |
Divide your motor output RPM by your desired output RPM to get the gear ratio. For example, a 3:1 reduction pairs a 10T drive gear with a 30T driven gear. Browse the 10T–38T variants in this listing to find the driven or drive gear that matches your target ratio.
Yes. Any gear conforming to the international Module 4 (Mod 4) standard with a matching 20° pressure angle will mesh correctly with these gears. Confirm the module and pressure angle of your existing components before ordering.
Material varies by variant. Common options for Module 4M gears in this class include carbon steel and aluminum alloy. Please check the variant detail or contact us to confirm the exact material for your selected tooth count.
Corrosion resistance depends on the material and finish of the specific variant. Steel variants may benefit from additional lubrication or protective coating in humid environments. Aluminum variants offer inherently better corrosion resistance. Contact us to confirm the finish for your chosen tooth count.
Bore diameter scales with tooth count and outer diameter. Because this listing covers 10T through 38T, bore sizes vary across variants. Please refer to the variant specifications or contact us with your shaft diameter before purchasing to ensure a correct fit.
Torque capacity depends on material, face width, and operating speed. Module 4M gears in steel are typically rated for moderate-to-high torque hobby and light industrial applications. For precise load ratings, consult the variant specifications or contact us with your application details.
Yes. The included set screw uses a standard metric hex (Allen) socket drive. A common M3 or M4 hex key (depending on the screw size for your variant) is all that is needed for installation and removal.
