Design, types, formulas & manufacturing basics
The visual guide starts here. Move from gear fundamentals to practical calculations and workshop considerations.
A toothed component that transmits motion and torque.
Power transmission • speed & torque conversion • direction change
Typical journey: Motor → Gearbox → Machine
Match the gear to the job.
Spur: parallel shafts
Helical: smooth and quiet operation
Bevel: intersecting shafts
Worm: high reduction
Rack & pinion: rotary → linear
Planetary: compact high-torque transmission
Understand the geometry before you calculate it.
Driver rotates
↓
Teeth engage
↓
Motion transfers
↓
Torque is transmitted
↓
Gear ratio controls speed
The involute profile helps maintain a constant angular velocity ratio.
Law of Gearing
The common normal at the contact point passes through the pitch point.
m = d / zd = m × zda = m × (z + 2)df = m × (z − 2.5)a = (d1 + d2) / 2i = z2 / z1Ft = 2T / d20 teeth • module 3 mm • 60 teeth • torque 50 N·m
20 teeth → 80 teeth
Pitch diameters = 80 mm and 320 mm
Input torque ≈ 98.8 N·m
Tangential force ≈ 2,470 N
Automotive • industrial machinery • robotics • appliances • medical • aerospace • renewable energy
Fatigue, wear, pitting, breakage and poor conditions can damage gears.
Maintain: lubricate correctly, inspect teeth, check backlash and alignment, monitor vibration/noise, keep gears clean, replace worn gears.
Work safely: use guards, follow lockout/tagout, wear appropriate PPE and handle heavy gear assemblies correctly.
References: AGMA, ISO 6336, DIN 3990, Machinery’s Handbook, Shigley’s Mechanical Engineering Design.
Workshop: correct cutter • correct setup • accurate measurement • proper inspection • good records.
Explore the complete Gear Engineering Guide and Engineer Data calculators.
Learn the theory. Check the formula. Calculate the dimensions. Build with confidence.