lapping arbor

[f350ca]

Lapping the bore on the mill will correct the alignment to bring it perpendicular to the flywheel. True he leaves it floating, in so doing he isn't correcting the position of the hole only the direction. Doing it on the lathe you won't be able to hold the flywheel perpendicular to the lap. The small bearing area of your bushing (assuming its square) won't support the wheel, it could wobble on the old hole as the lap turns. Any lapping I've done and that isn't a lot, was done with a lap softer than the bore, so the grit adheres to the lap and cuts the bore. I expect the flywheel is cast which probably is softer than the pin (probably hardened) so the pin will cut more than the bore, or the grit will simply roll around in the gap, which I expect is why he has to keep locating the grit. I'd make an aluminum or brass lap with the correct taper and do it in the mill after the mill was indicated as he says, proper term is tramed I think.
No written or implied guaranties but thats my take on it.