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Pressure angle (also referred to as “tooth shape”) is the angle at which the pressure from the tooth of one gear is passed on to the tooth of another gear. Spur gears come in two pressure angles: 14 1/2º and 20º. (See Figure above)

•The 14 1/2º pressure angle is the original standard tooth shape. It is still widely used today. (See Figure 2.4A)

• The new and improved 20º pressure angle tooth shape is a stronger and better tooth because of its wider base, especially on pinion gears with small numbers of teeth. (See Figure 2.4B)

IMPORTANT! 14-1/2º pressure angle gears will not run with 20º pressure angles gears – and vice versa!