What do you really get for a $350 desk top engraver ?

Y-axis:
3:1 reduction is fairly easy to do.  Motors can be flipped around so the output shaft points outboard, with the motor housing inboard using an off-set bracket that puts the motor behind the gantry.  Add a larger pulley to the drive pinion and you'll have an intermediate belt between the motor and the drive system. 

X-axis:
Not so easy as you don't have room on the gantry to 'flip' the motor around like on the Y above.  I'd suggest changing to a ballscrew for the X-axis for a couple reasons:

• Stiffer than a belt
  • Even with a no-backlash belt system, there is still compliance in the belt as the teeth flex.  Belts work rather well for plasma's and lasers, but the cutting forces on a router/mill will expose the problems with belt tooth compliance.  You can't eliminate this, just minimize it with larger belt profiles, wider belts, and more teeth engaged with the various pulleys.
• Doesn't distort the gantry
  • Tensioning the X-belt will/does bend the gantry and perhaps contributes to linear guide friction inconsistencies.
  • A ballscrew won't distort the gantry
• Easy to achieve the mechanical reduction.  A 16mm dia, 10mm pitch ballscrew is fairly inexpensive.  Probably less than (or close to) the cost of additional pulleys and belts, and the 10mm pitch means your motors won't be at some screaming RPM as with a 5mm pitch.

Or... just put ballscrews on all three joints.  No gearboxes needed, no pulleys, vastly improved stiffness, backlash easily managed.

And yes, you'll probably run in to the PS voltage ceiling one you get some mechanical advantage and need more RPM.

i like the belts to be honest. cutting soft material has very little cutting forces involved when finishing. i could care less what flexes while roughing as long as the finished part is good. belts shine on 3D tool paths with the quick acceleration and feed rates and was what attracted me to them in the first place I'm more interested in the high-speed machining applications with this machine

i tested a faster cut with the torque gains from micro stepping .600 deep with a ,130 step over @ 75 IPM with a 1/4 3 flute was impressive but ended up alarming the drive pushing that up to 104 IPM. it made the cut but with an alarm at the end. when you have the following error set at the factory 4,000 you don't alarm out but it shows up in the cut quality, the drive is trying to constantly catch up and shows up on the finish quality.

I'm pretty sure i can swing a reduction with some planning. i have a few weeks before i see my belts so now is the time to sort the design changes while i wait

i think i have a good design starting point for this reduction set up for my Y axis. the X will be easy comparted to the Y axis i think. i think i even avoided losing axis travel and should work well if i can make in come to life i think i will add a cover and rework my belt tension for the X axis into it but i think i have it compressed as much as i can work into this design,

   

Suggest making the cover a structural support that has outboard bearings for the pinion and belt idlers.

It need not be complicated - just a flat plate separated from the motor mount with standoffs and long bolts or threaded rods.  Some flanged bearings pressed in and longer pinion & idler shafts will keep belt tension from flexing the shafts.

Tension the main drive belt at the fixed ends so the pinion can remain fixed in relation to the idlers.

I'm using two tapered roller bearings in opposing directions to anchor the pinion and take out any lateral movement. i don't think that part is going anywhere. I'm using pretty large bearings in that part everything is on a 1" shaft with Anti-rotation ends locked on with M8 screws that will also preload the bearings. it's hard to show everything with a screen grab

1" shaft with tapered rollers?  Nice; disregard my last in that case.