Boston Model 19 Pencil Sharpener Gear for 10mm Shaft

[brianwsimms's gear](https://www.thingiverse.com/thing:267626) did not fit the Model 19 sharpener I was working with. The slot was too short and too wide. I modified it for a shaft with a diameter of 10mm and whose slot is 6.82mm wide. The hub was also made thinner to avoid rubbing on the motor winding.

Each of the STL files have a different tolerance. This is the how much the shaft opening is enlarged in the STL file. Bigger tolerances are looser on the shaft. For example, the 0.1mm toleranc