Cnc cutting the wrong size..

[JAZZCNC]

Sounds like you're now sorted (ie 100mm is cutting 100mm), if you're using Mach3 & have access to a dial indicator, here's how to get really granular with accuracy....

Purposefully didn't suggest using the auto feature has it doesn't really help Tom understand whats going off with his machine. Much better if you know the inner workings of the machine, makes fault finding and smooth operation much easier and quicker.

The belt is a 5mm pitch as for the ballscrew i dont know, any ideas how to find out also can this harm the machine or what problems will it cause.
Thanks

Ok well there's a few ways to find screw pitch but easiest way is to simply accurately measure the distance travelled for one full turn of the screw. This will give you pitch then you need to count the teeth on each pulley to find any ratio. (NOTE: 1 Turn of SCREW not MOTOR)

The belt pitch doesn't have any bearing on setting the steps per unit or distance travelled it's just the spacing between teeth.

The other way to find pitch is measure distance between the ball track centres. This technique works ok to give quick eyeball idea but it can catch you out if the screw is multi start.? Multistart screws are common with lead type screws and some of the higher pitch ball screws.
Basicly multistart use 2 or more tracks added together to give affective pitch per rev. IE: 10mm pitch with 2 starts each track will measure 5m centres.
The measuring distance travelled technique is preferred has it's more accurate and less prone to error.