Thanks for the reminder! I have a couple of Machtachs, one built up and working when I was living in a workshop-less rented house. Must get round to fitting it finally, now that I have my workshop!
As you can see from the link above, you can enter the diameter of the work (lathe) or cutter (mill) and it will tell you the surface speed rather than just the rpm, which is actually what you need much of the time. The alternative is looking up the required rpm from a table etc according to the diameter of the work / cutter and the material. This cuts out that extra step.
Nice piece of kit that went together nicely and just worked.
Murray