@Rob_Mitchell1
what setting are you using now? Not full step I hope! Full step is kind of weird. It is really coggy, and resonant.
@Rob_Mitchell1 if your at full steps, try 1/8 first. I seem to remember I had the same issue when I was using belts at low speed.
@Mark_Leino the controller was set at 1/8 step.
@Rob_Mitchell1 have you ever changed or checked the voltage settings of your drivers? I can’t remember the exact steps to check it, but there is a lot of info online about it. Probably first place to check would be documentation about the xpro. Just need a multimeter, tiny Philips screwdriver , and a steady hand or three 
Remember to change steps per mm. Should be twice as many as you have it set now, if you change to 1/16 micro stepping
@Rob_Mitchell1 your controller may reach 1/32 microsteps, the smaller the microstepping the smoother the motion
@Miguel_Sanchez
Motion is not necessarily smoothed out more with more microsteps. But resonance bands will certainly move around. I have had motors run smoothly even with just half step sequencing. Right now I am using quarter step sequencing, and it is smooth as can be.
Guys, I adjusted the stepping down to 1/32 and updated the steps/mm accordingly to 106.67steps/mm.
I still get chatter sounds and rough movement although the 1/32 did seem a little better.
I also adjusted the current pots but they didn’t help much.
Are your belts too tight? Wheels overly right? What size gt2 pulleys? Is your z axis also making this noise?
What speed (mm/min) are you trying to run at now?
If you jog an axis, does it sound the same? Did you adjust the motor drivers woke it was powered up, and use a multimeter? I don’t know all your info, but I think your steps/mm are off.
@Mark_Leino At higher speed jogs it’s a better sound (more smooth it would seem) then jogging at slower speeds. My intent is to cut PCB boards, real small ones. The video I posted is when the machine is “air cutting” a PCB at 300mm/min. When I look at the bit real close you can tell it’s rough movements. I’m afraid at the size I want to mill the board traces at (0.1mm) any side to side jaggy rough motion will not work.
My GT2 pulley is 20 tooth from openbuilds store. Pitch is 3mm, same as belt.
I adjusted the pots while the machine was powered up. As for using a multimeter I did not do that. not exactly sure where to connect the meter on this board.
From what I remember, check motor driver voltage from the pot screw head to ground. As far as what voltage your shooting for, I can’t remember.
Gt2 belt is 2mm pitch
If I’m not mistaken you should be at 160 steps per mm at 32 stepping. Note: that might not necessarily fix your issues though
Try bumping up to 400mm/min see if it helps
@Mark_Leino This is the pulley I have http://fuzztech.ca/shop#!/GT3-GT2-3mm-Aluminum-Timing-Pulley-20/p/38780247/category=9992288
And this is the belt…
http://fuzztech.ca/shop#!/GT3-GT2-3mm-Timing-Belt-By-the-Foot/p/39307672/category=9992288
I’m assuming both are 3mm pitch
Ah gt3 yep I watched your video again
How many lines of code is the program? Like was said before, it could be getting overloaded with too many movements to process properly. Is it over 5000? 10,000?
Just one more test I can think of, if you jog the machine 100mm on the DRO, does it actually move 100mm?
1/8 is fine, I don’t think it’s a micro step issue. Look at you acceleration settings and if you can the buffer level. What I think is happening is your gcode is in small segments and it’s completing each one stopping and then starting again. If you issue a long G0 command is it better?
@Paul_Shaw the PCB guide is smaller segments however if I send a command to Y with s/mm set to 300mm/min over a 400mm distance the result is the same. The acceleration setting is 300 for X&Y.