Just finished a new machine and configuring Mach3.

Under "set steps per unit" for my X and Y axis I get 1 inch of movement when I ask it to give me one inch so I have to assume that my steps per unit setting is correct, BUT manually driving either axis one inch (measured with my dial indicator) causes the display to read 10 inches

So my display reads actual measured movement * 10. G-code files are that ran just fine on my previous machine are thus one tenth the size I designed them to be.

Both the X and Y axis are belt drive via two pulleys. My Z runs on a lead screw and its display reads just fine.

Any help?

Sounds like you may be missing steps when jogging. Try MDI'ing a slowish feed and see if that works correctly, something like G1X1F5. If that travels the correct distance then your Acceleration is likely too high.
Hood

MDI'ing for one inch gives me one inch as best I can measure on the dial indicator and + 1.0006 on Mach3's screen.
Ill adjust my acceleration,, but its pretty conservative now. A manual move gives a slow ramp up and down rate.

Try reducing the Velocity, that way you may get better accel.
Also you may be needing a wider pulse, so that may be worth a try.
What do you have the kernel set to? Best to just have it as high as you need and not over.
Hood

Wider pulse seems to be helping...have to re-measure to be sure but movement seems more proportional now....

still losing steps - badly. I've tried every combination of settings both in mach3 and the hobbycnc driver board.
Both of the belt driven axis - X and Y - have the issue. The lead screw driven Z seems fine. Even with 1/1 stepping set and very conservative velocity and acceleration settings.

Steppers are 300 oz/in units from hobbycnc so I believe they're of decent quality and have enough power.  Driver board seems fine...wonder if I just hit on a motor, driver, gear ratio, etc, etc combo that just 'ain't going to work...

I'm stuck, and worse I've got a two week road trip starting this Wednesday and its going to nag me the entire time...(I'm kinda obsessive that way

Just poked at it again a bit more....could just be a coincidence but the onscreen scales still differ by x10 when i manually move the X and Y and the speed, accel, etc doesnt seem to matter, however i can still MDI for one inch and get exactly one inch.  Using the same computer as I did on my previous all lead screw machine so I think it should be ok

What is your setup?
In other words do your drives have microstepping? if yes what is it.
How exactly is your axis driven. You say belts  so I assume you are meaning you are using a toothed belt fixed to the frame and the motor has a pulley so that you are basically using the belt and pulley wheel as a rack and pinion set up?
If so what is the pitch of the belt and how many teeth on the pulley?
Hood

Try MDI a G0 and see if it still is OK, ie G0X1
Hood

Yes, just did. Asking for one inch gets me one inch. I don't know how it would do if I actually ran a Goode file because my spindle hasn't arrived yet...but I can zero the scales, manually move either x or y maybe  a foot or so and the actual distance moved will only be about 1/10th of what the onscreen scales show.