High-quality black-and-white photographs of large old machines and tools

[Frank S]

The name for the tooth pattern sometimes called a double helical but most often called a Herringbone. As I mentioned in another thread about the ability to transmit more torque with a helical than a straight cut gear the Herringbone design takes that to a far new level not only in the ability of handling increased torque the design does 2 more things it virtually eliminates lateral thrust plus can offer near zero backlash.
Here is a small pair of gear I have made out of aluminum



Here are a few examples of larger gear sets even right angle


Due largely to the double angle cut of the gears which in turn alters the stress angle in the body of both gears a higher ratio between pinion and bull can be obtained since there is also more tooth contact and more teeth in contact than a straight cut spur gear