Went to Wilson Engineering in Benfleet today. The chap could not have been more helpful & did a Rockwell test on the saildrive cutter I was copying. He pronounced it to be as "Soft as s..t" & that is why it has worn so much against the tufnol bearings. He has confirmed I can make the new one in Gauge plate & he will harden with absolute max of 10 thou distortion over 150mm on 6mm* 100 plate, which is acceptable
He has a minimum charge of £ 68-00 plus VAT & can do your items in one go provided one of them is not leaded steel.That would mean 2 separate items. He also lost me when he started describing 2 processes of hardening for those 2 steels.
But if you have someone to go & see already then you will have solved the issue anyway