Spur Gear 45# Steel Transmission Gear 1.5/2 Mod 12-27 Teeth With Step Motor Gear

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Spur Gear 45# Steel Transmission Gear 1.5/2 Mod 12-27 Teeth With Step Motor Gear

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By HomeDIYer®

Model: 1.5 Mod 12 Teeth

Bore Diameters: 6mm

Price:

$13.46 USD

Stock:

In stock (500 units), ready to be shipped

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45# Steel Spur Gear — Precision Transmission for DIY Automation & CNC Builds

When your motion-control project demands reliable torque transfer without backlash surprises, finding a spur gear that matches your shaft exactly can be a frustrating hunt. Hobbyists, makers, and small-workshop engineers building CNC routers, robotic arms, or custom conveyor systems need gears that are dimensionally consistent, easy to mount, and tough enough for continuous duty — not parts that arrive undersized or with sloppy bores.

These spur gears are machined from 45# medium-carbon steel, offering a solid balance of strength and machinability. Available in two module sizes — 1.5 Mod and 2 Mod — with tooth counts ranging from 12 to 27 teeth, and bore diameters spanning 6 mm (~0.24 in) to 25 mm (~0.98 in). Keyway variants (4 mm, 5 mm, and 6 mm keyways) are available for larger bores to ensure positive shaft engagement without set-screw slip.

Typical use cases include stepper-motor drive stages in desktop CNC machines, gear-reduction assemblies in educational robotics kits, and indexing mechanisms in small automated feeders — anywhere a compact, metric-pitch spur gear with a precise bore is required.

⚙️ Compatibility: Designed for metric module (Mod) gear systems. 1.5 Mod gears mesh with other 1.5 Mod gears; 2 Mod gears mesh with other 2 Mod gears. Verify module, pressure angle (typically 20°), and bore diameter before ordering.

✅ Key Features of These 45# Steel Spur Gears

🔩45# Medium-Carbon Steel Construction
Machined from 45# steel for reliable tensile strength and wear resistance in continuous-duty drive applications.

📐Dual Module Options — 1.5 Mod & 2 Mod
Two module sizes cover a wide range of gear-ratio and torque requirements, from compact stepper drives to heavier reduction stages.

🎯Wide Tooth-Count Range: 12–27 Teeth
Select the exact tooth count to achieve your target gear ratio without resorting to custom machining.

🔧Multiple Bore Diameters with Keyway Options
Bore sizes from 6 mm to 25 mm; larger bores available with precision-cut keyways (4 mm, 5 mm, or 6 mm) for positive shaft locking.

⚡Step-Motor Ready Hub Geometry
Hub dimensions are sized to suit common NEMA stepper motor shaft diameters, simplifying integration into CNC and automation builds.

📦Sold Individually — Mix & Match Variants
Each listing covers a single gear; order the exact module, tooth count, and bore combination you need without paying for parts you won't use.

📐 Technical Specifications — Spur Gears

Material	45# Medium-Carbon Steel
Module (Mod)	1.5 Mod / 2 Mod (see variant options)
Tooth Count	12 – 27 Teeth (see variant options)
Bore Diameter	6 mm – 25 mm (see variant options)
Keyway	Available on select bore sizes: 4 mm, 5 mm, 6 mm, 8 mm keyways
Pressure Angle	20° (standard metric)
Pitch Diameter (1.5 Mod)	18 mm – 40.5 mm (Mod × Teeth)
Pitch Diameter (2 Mod)	24 mm – 48 mm (Mod × Teeth)
Surface Finish	See variant options
Weight	See variant options
Quantity	1 piece per order

❓ Frequently Asked Questions

How do I choose between 1.5 Mod and 2 Mod?

Module (Mod) is the ratio of pitch diameter to tooth count. A higher module means larger, stronger teeth. Use 1.5 Mod for lighter loads and compact assemblies (e.g., small CNC axes, desktop robots). Use 2 Mod when you need to transmit more torque or when gear size is less of a constraint. Both gears in a meshing pair must share the same module.

What bore diameter should I select for my stepper motor shaft?

Match the bore to your motor's shaft diameter. Common NEMA 17 stepper shafts are 5 mm; NEMA 23 shafts are typically 6.35 mm or 8 mm. If your shaft diameter falls between standard bore sizes, choose the next size up and use a set screw or keyway to secure the gear. For shafts 12 mm and above, keyway variants are available for a more positive drive connection.

Are these gears strong enough for continuous-duty use?

45# steel provides a good balance of tensile strength (typically 600–800 MPa) and machinability, making it suitable for moderate continuous-duty applications such as CNC drive stages, conveyor indexers, and robotic joints. For very high-load or high-speed applications, consider whether surface hardening or a higher-alloy steel would be more appropriate for your specific torque and RPM requirements.

Do these gears resist corrosion?

45# carbon steel has moderate corrosion resistance. For indoor, dry environments this is generally adequate. If your application involves moisture, coolant, or outdoor exposure, we recommend applying a light machine oil or grease coating, or considering a stainless-steel alternative for your application.

Will a 1.5 Mod gear mesh with a 2 Mod gear?

No. Gears must share the same module to mesh correctly. Mixing modules results in incorrect tooth engagement, excessive noise, accelerated wear, and potential gear failure. Always confirm that all gears in your drive train share the same module value.

What is a keyway and do I need one?

A keyway is a rectangular slot machined into the bore that accepts a matching key inserted into the shaft. This creates a positive mechanical lock that prevents the gear from rotating on the shaft under load — unlike a set screw alone, which can loosen over time. If your application involves reversing loads, high torque, or vibration, a keyway variant is strongly recommended for bores 12 mm and above.

How do I calculate the gear ratio for my project?

Gear ratio = (Teeth on driven gear) ÷ (Teeth on driving gear). For example, pairing a 12-tooth drive gear with a 24-tooth driven gear gives a 2:1 reduction — the output shaft turns at half the speed but with twice the torque. Use this formula to select the tooth-count combination that achieves your target speed and torque output.

🛒 Select your Model (Mod & Teeth) and Bore Diameter above, then add to cart.