Having taken the advice of my betters and read some books, I made a
determined effort to get this to work, so perhaps a bit OTT but...
I took a short length of cast iron bar (ex casement weight) and drilled out
the middle to make a small pot. Then I ground up the Eternite to a fine
powder put the Eternite into the pot added in the tappets and cams tamping
down the Eternite between components, topped off with Eternite popped on a
little cast iron lid then warmed the whole lot upto big propane torch
temperature in an insulating cave made from old (modern) gas fire insulation
and kept it orange hot for 15 minutes and then left to cool for 30 minutes.
Then I quenched the pot retrieved the components, heated them back up and
quenched. Now the file won't touch it. Everything looks nice and evenly
baked and is polishing up well.
Apart from a charred workbench - the insulation wasn't quite as good as I
14 years ago