Interference in a pair of gears is avoided, if the addendum circles of both the gears intersect common tangent to the base circles with in the points of tangency.

For a pinion of $$15$$ teeth, under cutting ____________( increases / decreases) with _______________(increases / decreases ) of pressure angle.

Modern gear both profile is given involute shape because

For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon