1978 BobCat 8hp
Having a very hard time finding the small feeder/auger sprocket it is for #35 chain 8 tooth with a 1/2 inch plain bore. I can find a 8 tooth with a 3/8 bore thinking of machining to 1/2 or gearing up to 10 tooth what do you think?
Either bore it or cut down shaft to fit. I just finished upgrading 8/26 tracker replacing silly/cheap(unless you need to buy them) plastic bushings w flange ball bearings. I'll be looking to change chain size if I can't find suitable #35 sprocket if mine ever dies. I put new chain on this season and use the good lube used on my cycles.
Re: Bore or turn down the shaft. If it were mine, I'd look at which is easier and safer...Safer in that I'd be concerned how much "meat " would be left on the sprocket after boring it to 1/2"... furthermore an oops while boring out the sprocket has less consequence than turning down the shaft.
You just need the right equipment and expertise. I'm lucky to have on top of 60 yrs wrenching plus a degree in Industrial Arts Education. Unfortunately I don't have machine tools other than a grinder and drill press. That said a lot can be done the old way- I once resurfaced a damaged cam and rockers with a wet stone.