Shown below is a comparison of a used flywheel starter ring gear and an NOS Ford B-6384 gear. This same 112 tooth ring gear was used on all Model A, B, and V8 Fords from 1928 to 1948.
Because of the nature of the firing order on the Model A and B engine, the crankshaft and flywheel usually comes to rest in one of two spots opposite each other relative to the starter motor.
NOS Ford script gear is shown in front and used gear in the rear.
When the starter is engaged, the bendix teeth tend to usually hit the same areas of the ring gear and this leads to uneven wear and damage to the ring gear. This gear tooth damage and wear can then interfere with the ability of the bendix gear to smoothly engage the ring gear. This then causes the starter gear to jam and lock up while meshing with the flywheel ring gear.
If you are experiencing trouble with the starter jamming, it would be good to inspect the flywheel ring gear for damage and to replace it if necessary.
Shown above is a view of the type of damage and wear which is found on used ring gears (upper gear).