When I was building science museum exhibits I relied on WM Berg for precision mechanical parts. They never let me down.
They have a fantastic range of gears, belts, shafts, and bearings in many sizes and materials. This includes very small sizes and innovative belt systems.
They are not cheap, but everything is the best. Even browsing their catalog is fun. Take a look here, this is the metric catalog, they also have an inch version: https://www.wmberg.com/documentation/metric-catalog/metric_catalog.aspx
They have a fantastic range of gears, belts, shafts, and bearings in many sizes and materials. This includes very small sizes and innovative belt systems.
They are not cheap, but everything is the best. Even browsing their catalog is fun. Take a look here, this is the metric catalog, they also have an inch version: https://www.wmberg.com/documentation/metric-catalog/metric_catalog.aspx