Who'd have thought... Mark gummy metal with a sharpie...

[cropwell]

I can't see how a magic marker coating would be any use after the first pass, but maybe it is truly 'magic'.

I always thought that 'in tram' meant all axis movement was at right angles x to y and y to z. Maybe 'tram' is an acronym for True Right Angle Motion

[Snapper]

If it does actually work... it would be something you'd just do on a finishing pass. Could actually be quite handy for boring, I'm going to try it :)