A gear, shown in the picture, teeth is helixes shape and it is made on the inside of the cylinder.

It meshes parallel with a helical gear as long as twisted angel and twisted direction are facing the same side

Outer gears usually turn opposite side from each other when they mesh, but when an inner gear and an outer gear mesh, they turn towards the same direction.

An inner gear will always be larger, in other words, there will be a limitation on the number of tooth differences.

We can gear shave and gear grind as well.

We will solve any gear related problems.
We are glad to assess and suggest the solution to your problems..

http://www.kikuchigear.co.jp/