I have a 3axis cnc with mach 3  and Routcad software. But every time I draw something in cm in the Routcad then load the gcode in mach3 it starts to cut in a larger  scale.  I've checked everything I know of and it's all showing metric. Any help would be great

Change your units to mm.

Thanks for the reply, when I set up the machine w mach I used the mm , and when I go through mach and look around. The mm button is on.
So according to mach it's in mm.  My Routcad software uses cm . . Not sure what els to try.
Tom

Consult your Routcad manual. I would assume that you can select different units.
If MM is not available you could generate code in inches and use a converter to convert the code to MM.
You could also scale in Mach, have a look in the Mach manual for info.
BTW....never heard of Routcad 

RICH

Well I changed my steps from 640 to 320  and now it cuts perfect mm . But now when I'm cutting  a program  it seems to cut the holes good but then when it's time to cut out the object it starts half way up the material. 

when it's time to cut out the object it starts half way up the material.

 

You need to define how you want to machine something in CAM.  Know nothing about your software.


RICH

I have a similar problem; I am configured in inches. the X & Y cut fine, but the Z cuts in mm's.

mikesbeehives,
If the code is correctly generated in inches only, ie; no code to change the z , and the axis steps are correct for inches , and Mach config units are inches and no scaling, then Mach will generate the correct pulses for the move.
Maybe it's your external device or plug-in that is goofy.

RICH

If I zero everything after jogging to a max and then jog to the opposite Max., the x & Y dro are correct. The z dro is 54.2, when it has actually only moved 4".