I am making a spacer to fit a new quick change tool post to my Optimum D300 mini lathe. I am using 6mm flat steel plate. I cut it out with a hacksaw, drilled a 10mm dia. hole (my largest capability) and then had to square and clean up the edges and enlarge the hole to 17.95mm dia. I am busy shaping a boring bar to enlarge the hole, but this article is about squaring and cleaning the sides. I have a Proxxon BFW 40/E milling machine mounted on a Proxxon KT150 compound table. The book of words say this milling machine can mill steel, so I thought I would give it a go. The first pass with a 6mm end cutter went well (conventional milling) but on the second, the cutter snatched and almost gave me a heart attack. I'm not sure what was damaged (I can't see anything wrong and the spindle still measures perpendicular to the table - within 30 thou which is what it was before), but I realize I was climb milling and the depth of cut was too large, at least for steel. I re-planned the passes and finished the side without further mishap.
Two conclusions I have come to and if there is any advice, it would be appreciated.
Firstly the Proxxon BFW40/E can mill steel if you're careful about it.
Secondly, it seems that the final pass of any milling operation will be climb milling - I can't see any alternative. I attach a sketch showing the three passes that I finally used, the secret being in my opinion to make the amount of material to be removed on the final pass as small as possible.
Cheers
Brian