Calibration issues, advice needed

[JAZZCNC]

I have been out with the machine again, the MS drivers are still set to Jazz's settings and after calibration the 'steps per' on all 3 axes are between 1275 and 1286. It seems to cut at a reasonable rate according to the feed rates. I was expecting it to move quicker on rapids and jogging by hand.

That's a very high number of steps per.!! . . . The figures make think you have the Micro stepping set far too high and working on the steps per figures you have given I'd guess you have drives set at 6400 micro steps if using 5mm pitch screws or 3200 if 2.5mm pitch screws. In either case your set too high and should reduce to 2000 at most. Anything above this is just wasting pulses and robbing you of speed. If I'm correct then This will be why you can't get very high rapids.

So Please give details about machine.

#1 Are you using mm's or inch units in Mach3
#2 Micro steps drives set at.
#3 Ballscrew or lead screw pitch.

Edit: I've just been to your Intro and can see you have either 5mm or twin start screws so 10mm pitch so this confims to me you have the Micro stepping set way way to high.
Drop the micro stepping down to 1600 and if 5mm pitch set the steps per to 320. or 160 if 10mm pitch.

Now if the Kernal speed is set to 25Khz you should get in the region of around 4000mm/min velocity with Accel of around 800-1000s/s.

Raising the Kernal speed will allow more pulse rate so a higher velocity can be reached but I wouldn't go any higher than 45khz and even then I don't recommend you change it has every change from 35khz makes the machine potentialy unstable. You'll need a fast PC with good parallel port to higher than 45Khz.