Rear hub bearing

... a light push fit. Have you actually tried fitting it? It's located axially by being clamped between the central spacer tube and the dummy spindle. That tube is intentionally slightly longer than the internal distance between the outer race housings.

The outer race does need to be able to move axially to allow everything to line up. Axial location of the hub itself is achieved by the screwed bearing locator on the other side of the hub which positively locates that outer bearing race in its housing.

A bit difficult to describe.....

The double-row ball bearing (117DR) fits into the area at which you have pointed. The shouldered spacer ( p/n 18234 ) then inserts into the bearing.  Pack this space with grease and then fit the single-row ball bearing (117)  more grease followed by the small shouldered spacer,  felt washer and lock-ring/speedo drive.  Return to the brake side and using a soft metal drift ensure that the bearing is fully home in the recess, add more grease , then add the bearing cover washer, felt washer and felt washer retaining ring.  Use now a small punch or chisel to carefully indent the hub outer to hold all the parts in place.  The stub axle can then be fitted and the brakeplate with it spacer and nut / washer is ready to be fitted to the hub and swinging arm.  The hub is then held in place and the spindle , washer and spacer are inserted. When that's all located add the three hub to brakeplate long shouldered nuts and covers.  Have fun, cheers Howard   

Just looked at the early commando wheel i have. the double row bearing looks as if it sits in a steel sleeve (It does have a steel sleeve, I just checked with a small magnet) in the wheel hub. Your photo looks as if the hub bore has a steel sleeve.(It has, see above)  See if a small magnet sticks to it. If so, the sleeve has worn (most likely from a collapsed/seized bearing at some point in the past). Looking on the AN website it doesn't show an outer sleeve for this bearing so i don't think it is available as a spare. If so, you are now into the realm of finding someone to remove, manufacture and fit a new sleeve. Obviously don't carry on building the wheel as whoever you get to do the sleeve work will want just the hub to work with.   

The hub diameter : what bearing came out of it ?? 

Is there a makers number on it ?

Just wondering of someone has fitted a bearing with a larger O/D at some point to cater for wear.

The number ( or dimensions ) will allow you to get another bearing the same. 

I was going to say the same. Take a good look at what came out. It may have the steel ring attached.  Then read the number of the old bearing and find the data on line. It's possibly an oversize addressing a wear issue or the ring is attached to the original.
J

Richard - Perhaps a previous owner fitted a larger bearing to that side of the hub for competition work.  41.6 mm is about 1 5/8 inch so maybe the hub was opened out a little to  take an Imperial sized double-row bearing or even two single-row bearings.  Does your new double-row (4203) bearing fit tightly on the shouldered bearing spacer that goes into the hub ?  Also does the new single-row bearing fit correctly into the speedo-drive side of the hub ?  It may be possible to acquire a bearing to fit your hub.  I often get assistance from technicians at Diamond bearings in Eastleigh, Hampshire.  Tell them the I/d of the hub and the spacer o/d and see if they have anything.  Two single-row may suffice but they may not have the same quantity of balls as a double-row rigid type.  It may be less expensive than a new hub ........good luck, Howard