OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Removing drive roller from SB 590

Your right Grumpy it is cast iron

Close up of left side axle shaft


Close up of right side axle shaft


Close up of boss with part of ring gear, there is no key way securing it just a tight fit with the criss cross pattern to grip.
One little crack with age and it will start to spin.
The boss is one inch and a quarter high