I'm planning on buying a 3 phase, 1.5 Hp, TEFC motor and Hitachi VFD to replace the stock motor on my cnc'd X3.

http://www.amazon.com/3450RPM-230-460-C-Face-Baldor-VM3550/dp/B000BATM4Y

http://www.driveswarehouse.com/Drives/AC+Drives/Sensorless+Vector+VFD/SJ200-015NFU.html

I want to stop using the gearing in the X3, mount the new motor vertically, and directly drive the spindle with an L pitch timing belt and pulleys.

Does anybody have a suggestion for a timming pulley that could easily replace the stock spindle drive gear on the X3?

Will weight be an issue, and balance as the X3s motor mounts on the side of the spindle housing?

Weight will be an issue, especially at the top of the column. But a few shims and it should fix it. Post pics of this mod.
Any belt drive conversion will either require you to make your own spindle drive pulley from scratch, or to turn down the stock spindle gear, and bore a purchased pulley, so you have a nice tight interference fit. Some red loctite will help everything stay tight

Definitely will keep watching this thread. What kind of gear ratio are you looking at? I'd love to get a bit more speed and eliminate the gearbox losses/noise (although I can't say as mine has been anywhere near as noisy as I would have thought).

Good luck!

Cad, if you want to lose a great deal of noise, just do that conversion from the arceurotrade pdf. It's great, and pretty cheap. I did that in tandem with a pulley swap. Changed the motor pulley and the head pulley and now get 6000 in high, 3000 in low. The low is great for anything larger than a 10mm drill, and the high handles a 1/2in endmill at .1 DOC full on cutting a slot without breaking a sweat.

Last year I did a VFD 2hp conversion on a round column Enco Mill. I now am able to do all operations in a single belt position. I can go from 100 RPM with a big flycutter on steel, to 2600 RPM at 60 cycles for aluminum. It is possible to go to much higher cycles (90 or more) and get additional speed, but I have avoided that so far.

This conversion transformed the machine. It is quiet, vibration free and powerful. However, quality 3 phase motors that are properly insulated for VFD applications are big and heavy. My 2HP Leeson is at least 50 pounds. This was no problem on the Enco, but you will have to evaluate the weight/fit considerations on an X3. Big HP and VFD would be sweet on an X3!

Bill