Helical gears of the same hand drive shafts at right angles. In parallel shaft applications, the advantage of the helical gear design over spur gears is improved smoothness, with less noise due to the fact that the angled teeth engage more gradually and more than one tooth is in mesh at any time. In helical-worm speed reducers, a set of helical gears connected to the motor shaft drives a worm-gear set, Figure 3. The helical-gear set reduces input speed (from the motor) to the wormgear set. Spur gears and helical gears are two of the most common types of gears. They can often be used for the same types of applications; so what are the differences between helical gears vs. spur gears? Spur gears are the most common type of gear, and are also the most simple. They have straight teeth that are produced parallel to the axis of the gear.

HELICAL GEAR CALCULATIONS PINION GEAR No. Teeth = N = Number of teeth (t = pinion T = gear) Normal Pitch (DP) = DP = Normal Diametral Pitch ( pi/CP or [1/MOD] x ) Transverse DP = Trans DP = Norm DP * cos(HA) Circular Pitch (Inch) = Circular Pitch (mm) = Module (Inch) = Module (mm) = The article "Helical Gear Mathematics Formulas and Examples" appeared in the May/June 1988 issue of Gear Technology. Summary The following excerpt is from the Revised Manual of Gear Design, Section III, covering helical and spiral gears. This section on helical gear mathematics shows the detailed solutions to many general helical gearing problems.