Robin,

If you look at the picture below you can see how much of an offset it is... the bearing itself is quite thick and is side spilt. The main reason it is thicker on the split side is because the spindle is keyed to retain the bullgear and when you extract the spindle the key has to pass through the bearing. To give a strong positive drive they wanted to use a fairly substantial key and that meant they needed the bearing to be thick enough to allow a slot for the key to pass through (you can see the slot to the left in the pic, just above the split in the bearing, out of focus tho). But to have that thickness all round would have made it difficult to pinch down without straining the casting, so they offset it in the casting. Thats easy to do with a poured bearing and meant the casting didnt need to be too accurate. I suspect they had a jig that clamped to the bed with a long mandrel with a built-in key and this allowed them to pour both bearings at once and in alignment..