Hi Michael, have you seen this thread?
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=48230#Post48230I don't recall seeing a seriously cracked single deck SB45 before. It wouldn't have been an easy result to achieve. My guess is that it was caused by long-term running with the engine side clutch-half loose, due to the captive cotter having failed.
As you will notice from the other thread, your father's mower has the advantage of having a bolted-on deck, so there are two fairly practical ways to go. The first is to dismantle the deck by grinding off the welds holding its individual parts together, then repair the separate parts by welding and dressing them, then reassemble the parts by welding them together. The second is to just make a new deck, by measuring the parts of the old one and reproducing them, then welding them together. The second is probably easier, and is certainly better.
I think quite a number of Outdoorking people, and especially Deejay, will be very interested in this repair - particularly so if you make a new deck and publish the dimensions of each part.
