Variable ZZero

[waynelocke]

I have been having a problem getting a consistent zeroing with my zzero plate. Thinking that my old and abused plate might be the problem, I recently made a new one from some new plate aluminum and try to hit the same spot. I measured it with calipers and then tweaked it until it was dead on. This morning I needed an accurate depth for some veneer inlays and the zeroing routine gave settings between.008 above the material to ,020 above the material. It never seems to go to low. The Z axis seems tight. Any ideas.
Wayne Locke

[kerrazy]

What size bit were you trying to zero. Anything small than a 1/8 inch gives me problems, due to the geometry of the bit. even when you use a 1/8th end mill with either an upcut or down cut spiral you really only have a fraction of it contacting the z-zero plate, as the tip is machined on an angle. When I use any bits amaller than this I use a piece of paper between my material and the bit, and slowly move the z down just until it pinches the the paper but does not pierce it.

Food for thought, good luck, oh another thought, is there any way you could be raising your Z axis high enough to be racking it?
Dale

[ecnerwal]

I've not put on a Z Zero plate yet (predate them) but I think when I do I'll either use copper or a blank printed circuit board (copper foil and fibreglass) rather than aluminum. Don't know how much difference it will make, but copper is a better conductor, and does not coat itself with insulating oxides. I also recall seeing that Gerald had a buch of extra grounding cables on the machine to make sure that the ground connection to the router was good (I'm guessing).

[gerald_d]

That's right Lawrence, we would never trust a couple of grease filled bearings to make the ground path for us. Also for the sake of the bearing, we don't want electrical currents causing pitting/erosion on the finely polished balls and raceways inside.