I share your pain.
I've tried to get my normal go-to people in the UK to have a go at the splines in the pic here. Drawn a blank so far. 'Risk of distortion' plus 'risk of subsequent breakage', 'cast iron difficult, especially with hollow mainshaft' etc.
Advice has been to find another - but I am reluctant to scrap an otherwise good item.
An owners' club member with a similar problem - and bigger lathe and miller plus far better skills than me - tells me he Tigged his, recut the splines on his miller, and has since done 25,000 km or more without disaster.
Says it can be done though, if one can find the right person . . . but no idea of cost of course. Serious, sure, but so's finding another crank, regrinding etc etc etc.
(Plan B in my case would be to lock up the crankshaft shock absorber, ditching the spring and making suitable spacers, and find / fit / modify a clutch with a cush drive centre. Which is I think do-able using AMC parts. Is that do-able on an A if using a 4-spring Tri-type with the inserts?)
