19 tooth countershaft sprocket

[marel_imp]

nice welding and turning to make that work well.

Indeed. You need a tight fit to keep concentricity right and to keep the pinion plane perpendicular to its axis. Any miss alignment will create vibrations and increase fatigue loads.

Also, I'd be a bit concern about the heat-affected area by the weld. It seems far enough from the hardened surface (pinion faces and spline), but perhaps some stress-relieving wouldn't be a bad idea to avoid a fatigue failure.

Indeed. You need a tight fit to keep concentricity right and to keep the pinion plane perpendicular to its axis. Any miss alignment will create vibrations and increase fatigue loads.

Also, I'd be a bit concern about the heat-affected area by the weld. It seems far enough from the hardened surface (pinion faces and spline), but perhaps some stress-relieving wouldn't be a bad idea to avoid a fatigue failure.
This "invention" was already balanced and seems to be more/less ok - it has a small run-out.
Both sprockets come from the same manufacturer and have the same thickness (and metal alloy?). The inner sprocket was dedicated to SC65, so really I hope will work as should be...