Spur Gear 1/1.5/2/2.5/3/4/5 Mod 12T - 150T Flat Gear 45 Steel Transmission Gears

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Spur Gear 1/1.5/2/2.5/3/4/5 Mod 12T - 150T Flat Gear 45 Steel Transmission Gears

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By HomeDIYer®

Modulus: 1Modul

Teeth-OD: 12T - OD 14mm

QTY(Pcs): 1

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$4.43 USD

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In stock (500 units), ready to be shipped

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Spur Gear 45 Steel — Precision Flat Transmission Gears for Demanding Drive Systems

When a slipping or mismatched gear brings your build to a halt, you need a replacement you can trust to spec. Engineers, robotics builders, and CNC hobbyists working on power-transmission projects require spur gears with consistent tooth geometry, reliable material hardness, and a broad size range — all in one catalog. These 45 steel spur gears are machined to standard modulus tolerances, making them a direct fit for most metric gear trains without custom modification.

Each gear is machined from 45 steel (medium-carbon steel, equivalent to C45 / S45C), a material known for its balanced combination of tensile strength and machinability. The flat-face (no hub) profile keeps axial length minimal. Available in seven modulus values — Mod 1, 1.5, 2, 2.5, 3, 4, and 5 — with tooth counts ranging from 12T to 150T and outer diameters spanning approximately 14 mm (0.55 in) to 152 mm (5.98 in) depending on the selected modulus and tooth count.

Typical applications include DIY CNC router axis drives, desktop robotic arm joints requiring a compact spur gear set, small-batch automation conveyor reduction stages, and 3D-printer extruder or Z-axis transmission upgrades. The standardized modulus system means these gears mesh directly with any mating gear of the same modulus and pressure angle, simplifying replacement and multi-stage gearbox design.

⚙️ Compatibility: Meshes with any standard metric spur gear of the same modulus (Mod 1 / 1.5 / 2 / 2.5 / 3 / 4 / 5) and 20° pressure angle. Verify bore diameter and keyway requirements before ordering.

✅ Key Features of These 45 Steel Spur Gears

🔩 45 Steel Construction

Medium-carbon 45 steel provides a tensile strength of approximately 600–800 MPa, offering solid load-bearing capacity for light-to-medium duty transmission applications without the cost of alloy steel.

📐 Seven Modulus Options

Available in Mod 1, 1.5, 2, 2.5, 3, 4, and 5 — covering the most common metric gear standards. Select the modulus that matches your existing gear train for direct mesh compatibility.

🔢 Wide Tooth Count Range

Tooth counts from 12T to 150T (modulus-dependent) let you achieve a broad range of gear ratios within a single product family, reducing the need to source from multiple suppliers.

📏 Flat-Face Profile

The hubless flat-face design minimizes axial space consumption, making these gears well-suited for compact gearboxes, stacked gear stages, and space-constrained robotic joints.

⚡ Standard 20° Pressure Angle

Machined to the industry-standard 20° pressure angle, ensuring smooth meshing, predictable load distribution, and straightforward interchangeability with other standard metric spur gears.

📦 Flexible Quantity Options

Available in single-piece (1 pc) or two-piece (2 pc) packs depending on the selected modulus and tooth count, allowing you to order exactly what your project requires.

📐 Technical Specifications — Spur Gears

Material	45 Steel (Medium-Carbon, C45 / S45C equivalent)
Gear Type	Spur Gear (Flat Face, No Hub)
Available Modulus	Mod 1 / 1.5 / 2 / 2.5 / 3 / 4 / 5
Tooth Count Range	12T – 150T (range varies by modulus; see variant options)
Outer Diameter Range	Approx. 14 mm – 152 mm (0.55 in – 5.98 in); see variant options
Pressure Angle	20°
Face Width (Tooth Width)	See variant options
Bore Diameter	See variant options
Surface Finish	Machined (natural steel finish)
Pack Quantity	1 pc or 2 pcs (see variant options)
Applicable Standards	Standard metric modulus system, 20° pressure angle

❓ Frequently Asked Questions

How do I choose the correct modulus for my application?

The modulus must match the mating gear in your drive system. Measure the outer diameter (OD) of an existing gear and divide by (tooth count + 2) — the result is the modulus. For example, a 20-tooth gear with an OD of 22 mm has a modulus of 22 ÷ (20 + 2) = 1. Select the same modulus value from the variant options above.

What gear ratio can I achieve with these spur gears?

The gear ratio equals the tooth count of the driven gear divided by the tooth count of the driving gear. For example, pairing a 12T driver with a 60T driven gear gives a 5:1 reduction ratio. With tooth counts from 12T to 150T available in this range, you can achieve ratios from approximately 1:1 up to 12.5:1 in a single stage.

Are these gears strong enough for my CNC or robotics project?

45 steel has a typical tensile strength of 600–800 MPa and yield strength of approximately 355 MPa, making it suitable for light-to-medium duty power transmission — including desktop CNC routers, robotic arms, and small automation systems. For heavy-duty or high-speed industrial applications, consider alloy steel or heat-treated gears. If you are unsure, contact us with your torque and speed requirements.

Do these gears require any surface treatment or lubrication?

The gears are supplied with a natural machined steel finish and are not pre-treated or coated. For outdoor or humid environments, applying a light machine oil or grease will help prevent surface oxidation and extend service life. For enclosed gearboxes, standard gear oil or grease lubrication is recommended.

Will these gears mesh with gears from other brands or suppliers?

Yes — as long as the mating gear shares the same modulus value and 20° pressure angle, these gears will mesh correctly regardless of brand. This is the standard metric spur gear specification used globally. Always verify the modulus, pressure angle, and bore diameter before assembling.

How do I determine the correct tooth count for my gear ratio and center distance?

Center distance (C) between two meshing spur gears is calculated as: C = (T1 + T2) × m ÷ 2, where T1 and T2 are the tooth counts of the two gears and m is the modulus. Rearrange to find the tooth counts that satisfy both your required gear ratio and your physical center distance constraint. Select the Modulus and Teeth-OD variant combination that fits your design.

What is the difference between the 1 pc and 2 pc quantity options?

The QTY(Pcs) option lets you select either 1 piece or 2 pieces per order line (availability varies by modulus and tooth count). Ordering 2 pcs is useful when you need a matched pair for a symmetric drive stage or want a spare on hand. The price shown reflects the per-pack cost for the selected quantity.

🛒 Select your Modulus, Teeth-OD, and QTY above, then add to cart.