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When a stripped or undersized gear brings your CNC router, automated conveyor, or robotics build to a halt, you need a replacement that holds tolerance under load — not one that wears out in the first hundred cycles. Engineers, makers, and machine builders who demand repeatable accuracy turn to Module 4.0 spur gears machined from 45# carbon steel for their drive trains.
This listing covers a complete range of Module 4.0 flat spur gears spanning 10T through 50T tooth counts. Each gear is machined from 45# medium-carbon steel (equivalent to SAE 1045), offering a tensile strength typically in the 600–800 MPa range before any additional heat treatment. Tooth pitch diameter scales with tooth count at 4 mm per tooth (e.g., 10T = 40 mm / 1.57 in PD; 25T = 100 mm / 3.94 in PD; 50T = 200 mm / 7.87 in PD). Bore diameter and keyway dimensions vary by tooth count — see variant options for exact bore specs.
Typical use cases include CNC milling machine Z-axis drives requiring consistent backlash control, open-frame 3D printer extruder gear trains where module 4.0 spur gears for RepRap-style builds are needed, and light industrial conveyor reduction stages where a flat spur gear transmission gear for automation lines must mesh reliably with a matching pinion.
Machined from 45# medium-carbon steel for a balance of machinability and load-bearing strength, suitable for moderate-to-heavy drive applications.
Involute tooth geometry cut to Module 4.0 standard ensures smooth meshing and interchangeability with any Mod 4 mating gear or rack.
40 tooth-count variants in a single listing let you dial in the exact gear ratio your drive system requires without sourcing from multiple suppliers.
Parallel-axis flat gear profile transmits torque efficiently with minimal axial thrust, ideal for compact gearbox assemblies and open-frame machine builds.
Dimensioned for direct drop-in use on CNC routers, laser cutters, conveyor reduction stages, and robotics joint drives where a reliable transmission gear is critical.
Each order ships as 1 PCS, letting you order exactly the quantity you need for prototyping, replacement, or small-batch production runs.
| Module | 4.0 (Mod 4) |
|---|---|
| Tooth Count Range | 10T – 50T (see variant options) |
| Material | 45# Carbon Steel (SAE 1045 equivalent) |
| Gear Type | Flat Spur Gear (parallel axis, involute profile) |
| Pitch Diameter | Module × Teeth (e.g., 4 × 20T = 80 mm / 3.15 in) |
| Pressure Angle | 20° (standard involute) |
| Bore Diameter | See variant options |
| Hub / Face Width | See variant options |
| Surface Finish | Machined, natural steel (no coating unless noted) |
| Packing Quantity | 1 PCS per order |
| Application | CNC machines, robotics, conveyor drives, automation |
Gear ratio is determined by dividing the driven gear tooth count by the driving gear tooth count. For example, pairing a 10T pinion with a 40T gear gives a 4:1 reduction. Calculate the ratio your drive system requires, then select the tooth count that achieves it while keeping the center distance within your frame constraints (center distance = Module × (T1 + T2) / 2).
45# carbon steel has a typical tensile strength of 600–800 MPa in the as-machined condition. Actual load capacity depends on tooth count, face width, operating speed, and lubrication. For high-cycle or high-torque applications, consider specifying heat-treated variants or consult a mechanical engineer for a formal gear strength calculation (AGMA or ISO 6336).
45# carbon steel is not inherently corrosion resistant. For outdoor, humid, or washdown environments, apply a suitable lubricant or protective coating (e.g., grease, oil, or zinc spray). For applications requiring inherent corrosion resistance, consider stainless steel gears instead.
Yes — any two gears sharing the same module and pressure angle will mesh correctly. These gears use Module 4.0 with a standard 20° pressure angle, so they are interchangeable with any Mod 4 / 20° rack, pinion, or mating spur gear regardless of brand, as long as the tooth count combination gives you the center distance your frame allows.
Bore diameter varies by tooth count and is listed in the variant detail page. Measure your shaft diameter with a caliper before ordering. If the bore is slightly larger than your shaft, a keyway and set screw arrangement or a shaft collar can take up the slack. If the bore is smaller, the gear cannot be installed without machining — contact us to confirm bore specs for your selected tooth count.
Yes. Module 4.0 spur gears are commonly used in CNC router rack-and-pinion drive systems, laser cutter gantry drives, and similar motion control applications. Ensure the pinion tooth count and motor torque are matched to your required feed rate and cutting force. A 20T–25T pinion paired with a Mod 4 rack is a common starting point for desktop CNC builds.
Yes. Steel-on-steel gear meshes benefit from lubrication to reduce wear and operating temperature. A light machine oil or lithium-based grease applied to the tooth flanks at installation and periodically during service will significantly extend gear life, especially in continuous-duty or high-speed applications.
