WPS05/21B-4 Metric Moulded Hostaform Spur Gear 21 Tooth 0.5 Mod Bored 4mm (H9)

Metric Moulded HOSTAFORM 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 instances lubrication is not required, gears potentially subject to severe weather or chemical exposure may require some form of lubrication and protection selected specifically for that application. eg: waterproof enclosures etc but in the vast majority of applications nothing is required.
Material: Hostaform offers an enhanced balance of strength, stiffness and toughness over a broad temperature range, improved long-term fatigue resistance at high temperatures for applications where the material may be exposed to higher levels of mechanical and cyclic stresses. It is a tough, hard material and is readily machineable.
Benefits: High quality, good tensile strength, stiffness and temperature resilience, pre-bored to H9 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.
Gear modulus 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.