Ok a bit more about the Mill, will try and keep it short, this concerns the rollers as it is probably the most interesting.
The whole process began with me obtaining some rollers ( well known Brand ) for no cost another story, these rollers turned out to be not usable, unfortunately the "Build you own mill" infection was to far advanced for me to stop now, sol I raided my I will need that one day section of my shed and found a section of 4340 steel, I only have a small lathe the stock just fitted into the chuck, I roughed down to size, the finished between centres leaving 1mm to finish later, to cut the grooves I hand ground purpose shaped tools for each one from HSS, then finished the two rollers to .5 mm. Now I needed to get them hardened.
My partner Cait works for a very large aerospace company they have a small research and prototype shop, I spoke to Colin who said we have a small induction machine that should do the job, sounds like a good apprentice training job, and I get to watch. The rollers were passed through two induction coils heating them to a bright red and immediately cooled by liquid nitrogen sprayed from as set of nozzles just below the induction coils. The rollers were then placed in a computer controlled
heat treatment oven controlled ramp up and ramp down, result hardened to depth of 3.2 mm at 65 RC. Collin then said I suppose you want us the finish them (silly question) .
The machines used for finishing are in a clean room, so disposable overalls and hair bonnet have to be worn, the rollers were roughed finished in the main workshop, Colin mounted them in a precision lathe that runs on air bearings has a tolerance of .1 micron ( you can have one for just $2.3 million ), the cutting tip is a diamond, the lathe was programed at let do it's thing, fascinating watch, no pics (no image or sound recording devices allowed). The rollers came of the lathe looking as though they had been polished, no further work needed, I probably have the most hi tech set of rollers on the planet way over kill. But in the end they still cost me nothing.