wanting to remove the stanchions and steerer from some Rockshox Revs
and make a new crown with a view to fitting them on the fatty

just wondering how they are fixed in

bonded, with a possibility of a heated crown and frozen stanchions.

You won’t get a decent re-bond either, your best bet will be pinch bolts like on dual crown forks. If you smack it with a hammer enough times it should come out but may damage the steerer, no idea how you would get stanchions out but “carefully” is my guess.

If you’re making a new crown anyway, I’d make 2 cuts in the crown to release each of the pressed in pieces. If you got both cuts nearly through the crown, a sharp blow may finish the job by cracking the crown w/o cutting into the stanchion/steerer.