To do or not to do, can it be done? MK4 drill steel.

[Neale]

Seeing that you've quoted my design, I might as well jump in here! I am extremely pleased with the way my AVOR machine has worked out - much better than planned. As a model engineer rather than a woodworker, I've been doing a lot of work in steel recently. For example, cutting the external profile of small steel components (maybe 10mm or so square) and then turning them through 90 deg and slotting. However, I only have the usual router-type spindle nominally rated down to 6K RPM, and it's possible to get it bogging down and slowing (to the point that I have worn out carbide cutters) even then. So, I run at, typically, 7K+ RPM, with carbide cutters in the range 2-4mm. I would cheerfully cut a 25mm hole through steel with this - in fact, I have done through something like 3mm hot-rolled steel - but I do it with an internal contour cut rather than drilling out all the waste. My machine does fine with this, and certainly to the kinds of accuracy you are talking about. When I first saw your requirement, my immediate thought was that I would do it my way, in effect trepanning/annular cutting but with a small milling cutter moving in a circular path. I didn't say anything because whether or not this would work for you depends on a bunch of other factors, like how many, how fast you need to cut them, how deep, etc. From a design point of view, loads on the machine are much reduced compared with drilling but it would be much slower than a machine capable of putting a 25mm drill through steel. In fact, I wouldn't try to do that even with my vertical mill - that's quite some cut.

There is something else to remember, and that is that a CNC machine, properly set up and with appropriate ways to clear chips, will run happily without someone standing there doing anything. So the fact that a job might take longer is offset by the fact that you can be getting on with something else at the same time.

I'm rambling a bit, I know, but although I haven't carried out any formal analysis on it, my gantry design is pretty stiff and capable of handling the kinds of loads my spindle/cutter combinations can throw at it. YMMV!

[Oldtech]

Also Neale, your machine looks very stout, has the gantry weight presented any issues? I think you said you used NEMA 23 would 34 be better? Twin screws on Z axis?