SS40/21B-20 Metric EN8 Spur Gear 21 Tooth 4 Mod Pilot Bored 20mm (H8)

Metric Steel Spur Gears: Spur gears are one of the most common type of gears. They have straight teeth and are generally mounted on parallel shafts. They are designed to exchange speed for torque or vice-versa between input and output shafts, dependent on the gear ratios chosen they can step-up / down the output speed or torque.
Lubrication: In most cases standard lubrication by oils or greases is acceptable, gears potentially subject to severe weather or chemical exposure should have their lubrication and protection selected specifically for that application. eg: waterproof grease etc.
Material: EN8 Steel - a medium strength steel with good tensile strength manufactured to DIN standards. It can be through hardened and is readily machineable in any state.
Benefits: High quality, good tensile strength EN8 Steel, pre-bored to H8 tolerance, high quality off the shelf component.
Gear Geometry and Modulus or Mod: The reality of gear geometry and modulus is it can become quite complicated but the rule of thumb is to only use gears of the same modulus together.
The modulus of a gear is a ratio calculated from the gear diameter at half its tooth height divided by the number of teeth, gear modulus must be the same between connecting gears in a drive train, bigger mod ratios have fewer teeth and will transfer larger amounts of power, smaller mod ratios will tend to be in faster and quieter applications.