Gear Selection Guide
Selecting the right gear for your application involves five key decisions: gear type, material, module, face width, and precision grade. This guide walks through each step.
Step 1 — Choose Gear Type
Spur Gears: Parallel shafts, simple design, most economical. Best for moderate speeds.
Helical Gears: Parallel shafts, quieter operation, higher load capacity. Preferred for higher speeds.
Bevel Gears: Intersecting shafts (typically 90°). Use Miter gears when ratio = 1:1.
Worm Gears: Non-intersecting, non-parallel shafts. High ratios in compact space. Self-locking at high ratios.
Gear Racks: Rotary to linear motion conversion.
Step 2 — Select Material
For general industrial use: S45C carbon steel. For corrosion resistance: stainless steel (SUS303/SUS304). For light-duty, low-noise: MC Nylon or acetal (POM). For food/medical: stainless or food-grade plastic.
Step 3 — Calculate Module
Use Lewis bending stress analysis with your required torque and speed to determine the minimum safe module. Then select the next standard module size up.
Step 4 — Determine Face Width
Standard face width: 8m to 12m (8 to 12 times the module). Wider faces increase load capacity but also increase weight and alignment sensitivity.
Step 5 — Specify Precision Grade
JIS N8–N9 for general use. JIS N6–N7 for precision machinery. JIS N5 for high-precision positioning. Higher grades cost more but provide tighter tooth profiles and reduced backlash.