Involute gears (spur and helix)

This is the customizer for gears in Mechanical Parts Library (http://www.thingiverse.com/thing:1427673). This script can generate spur, helix and double helix gears.This is the only script I have seen to include cutoff, which is very important for gears with low number of teeth. Without cutoff, meshing gears may got stuck. Additionally, this script can generate different spacing patterns and mounting hole shapes. It is possible to generate screw hole and support. Finally you could enable handle