I have heat treated in a gas forge for heat treating 52100 but, as stated above, it not ideal. As with all hypereuticoid steels it's easy to put too much carbon into solution and then create a problem with retain austenite. If soaked at too high of a temperature you can also run into a problem with grain growth. It's helpful if you can spot decalessence. That way you can try to keep the steel at the same brightness it had when the last of the shadow passed from the steel and try to hold it there for about 10-15 minutes. At the same time you have to keep the shadow from reappearing which would indicated recallesense and conversion of the iron structure back the the body centered cube.
As far as what you need to do before grinding I assume that you are talking about stock removal with steel from a supplier. It should come to you ready to grind so you shouldn't have to do anything to prepare it. You may even be able go get by without thermal cycling to adjust the grain size. You should, however, normalize once to relieve any stresses in the steel from production or grinding and then proceed to hardening process. If you are going to try spotting decalessance or recalessance you should do so under dim light.
Doug
