4 Modulus Spur Gear 10T - 22T Flat Gear 45 Steel Transmission Gears OD 48-96mm

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4 Modulus Spur Gear 10T - 22T Flat Gear 45 Steel Transmission Gears OD 48-96mm

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By HomeDIYer®

Modulus: 4Modul

Teeth-OD: 10T - OD 48mm

QTY(Pcs): 1

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$24.82 USD

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In stock (500 units), ready to be shipped

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Module 4 Spur Gear — Precision 45 Steel Flat Gear for Reliable Power Transmission

When your drive system demands consistent torque transfer and dimensional accuracy, an undersized or poorly machined gear becomes the weakest link in the chain. Engineers, robotics builders, and machine designers who need a dependable module 4 spur gear with a verified tooth profile will find this flat gear a direct fit for demanding mechanical assemblies.

Each gear is machined from 45 steel (medium-carbon steel, equivalent to C45 / S45C), offering a balanced combination of strength and machinability. The module 4 spur gear range covers 10 teeth to 22 teeth, with outer diameters spanning 48 mm to 96 mm (approximately 1.89 in to 3.78 in). Tooth width (face width) is consistent with standard module 4 geometry; bore diameter varies by tooth count — see variant options for exact bore dimensions.

Typical applications include CNC router axis drives, robotic arm joint transmissions, conveyor indexing mechanisms, and small-batch automation equipment where a module 4 spur gear with a flat (non-helical) tooth profile is specified. The straight-tooth design simplifies alignment and allows axial assembly without thrust bearing considerations, making it a practical choice for parallel-shaft gear reduction stages and DIY power transmission projects.

⚙️ Compatibility: Meshes with any standard Module 4 (Mod 4) spur gear, rack, or pinion. Verify center distance using the formula: CD = (T₁ + T₂) × m / 2, where m = 4 mm.

✅ Key Features of These Module 4 Spur Gears

🔩 45 Steel Construction — Medium-carbon steel delivers solid tensile strength and wear resistance for sustained mesh loads in industrial and hobbyist drive systems.

📐 Wide Tooth-Count Selection — 10T through 22T in a single listing; outer diameters from 48 mm (1.89 in) to 96 mm (3.78 in) to match your gear ratio requirements without custom machining.

⚡ Standard Module 4 Tooth Profile — 20° pressure angle, straight spur tooth geometry; fully interchangeable with any Mod 4 mating gear or rack on the market.

🎯 Flat Gear Design — No helix angle means zero axial thrust force, simplifying shaft and bearing selection in parallel-axis gearbox builds.

🔄 Multi-Piece Quantity Options — Available in packs of 1, 2, or 3 per order; ideal for building matched gear pairs or stocking spares for ongoing production runs.

🛠️ Machinable Bore — Standard bore can be re-bored or keyway-cut to match your shaft diameter, giving flexibility for custom shaft fits in prototype and small-batch builds.

📐 Technical Specifications — Module 4 Spur Gear

Module (m)	4
Pressure Angle	20°
Tooth Type	Straight spur (flat gear)
Teeth Range	10T – 22T
Outer Diameter (OD) Range	48 mm – 96 mm (1.89 in – 3.78 in)
Material	45 Steel (medium-carbon, C45 / S45C equivalent)
Surface Finish	See variant options
Bore Diameter	See variant options
Face Width (Tooth Width)	See variant options
Hub Diameter	See variant options
Keyway	See variant options
Quantity per Pack	1 / 2 / 3 pcs (select above)

❓ Frequently Asked Questions

How do I choose the right tooth count for my application?

Select tooth count based on your required gear ratio and available center distance. For a 2:1 reduction, pair a 10T pinion with a 20T gear. Center distance (CD) = (T₁ + T₂) × 4 / 2. Smaller tooth counts produce more compact assemblies; larger tooth counts distribute load across more teeth for smoother, quieter operation.

What is the load capacity of a Module 4 spur gear in 45 steel?

45 steel has a typical tensile strength of 600–800 MPa and yield strength of approximately 355 MPa in the normalized condition. Actual gear load capacity depends on tooth count, face width, operating speed, and lubrication. For high-cycle or shock-load applications, consider surface hardening (induction hardening or case hardening) after machining the bore to your shaft size.

Are these gears corrosion-resistant?

45 steel is a carbon steel and will oxidize if exposed to moisture without protection. For corrosion resistance, apply a light machine oil, grease, or a surface coating such as black oxide or zinc plating after installation. For environments with continuous moisture exposure, consider stainless steel or plastic gears instead.

Will this gear mesh with my existing Module 4 rack or pinion?

Yes. Any gear or rack manufactured to the Module 4 standard with a 20° pressure angle will mesh correctly with these gears. Confirm the module and pressure angle of your existing components before ordering. Module 4 is not interchangeable with DP (diametral pitch) gears — if your existing system uses DP gearing, you will need a conversion.

Can I re-bore or add a keyway to the standard bore?

Yes. 45 steel machines well on a lathe or mill. The bore can be enlarged and a keyway or set-screw flat can be added by a machine shop to match your shaft diameter. Ensure sufficient hub wall thickness remains after boring — contact us to confirm hub dimensions for your selected tooth count before machining.

What quantity options are available, and when should I order multiples?

Each variant is available in packs of 1, 2, or 3 pieces. Order 2 when building a matched gear pair (e.g., input and output gears of the same size for a parallel shaft). Order 3 when you need one installed gear plus spares for a production run or field maintenance kit. Buying in a pack is more economical than separate single-piece orders.

What is the difference between a flat spur gear and a helical gear, and which should I choose?

A flat (straight-tooth) spur gear has teeth parallel to the gear axis, producing no axial thrust force. This simplifies bearing selection and assembly. Helical gears have angled teeth that engage more gradually, resulting in quieter operation and higher load capacity, but they generate axial thrust that must be managed with thrust bearings. For most DIY, robotics, and light industrial applications, a straight spur gear is the simpler and more cost-effective choice.

🛒 Select your Teeth-OD size and quantity above, then add to cart.