Here are installation instructions for the X2 minimill kit with ballscrew upgrade on the X-Y axis.
Step1 Table Removal
Remove the Y axis handwheel, handle block & Y axis screw, and the brass nut.. Keep the original Y axis cap screws, you will use them later. Remove the small plate at the left end of the table, thats opposite the X axis handwheel. You will not need the two screws that hold this plate in place, you will use 6mm cap screws that come with the kit. Remove the X axis handwheel, and thrust bearing plate. Loosen the X axis gib screws and remove the table. Remove the X-axis leadscrew, and brass nut.
The Y axis motor mount and ballscrew will come pre-assembled as shown in this photo. Remove the ballscrew from the Y axis motor mount by loosening the locking collar and coupling. Push the saddle back toward the column as far as possible. Lay your mill on it backside. From underneath the mill, feed the ballscrw through the hole in the base, while at the same time inserting the aluminum ballnut mount into the slot that held the original brass nut. Snug up the locking screw that secured the original brass nut, this will hold the ballscrew in place while you stand your mill back up. Stand mill back upright. Pull the saddle forward, so the ballscrew is now sticking out the hole in the base far enough to slide the Y-axis motor mount onto the end of the ballscrew. Re-assemble the Y-axis motor mount to the ballscrew. Be sure to get the collar tight against the bearings. Push the saddle back so the motor mount is against the base, and you can insert and tighten the two 6mm cap screws that secure the motor mount. You will also want to loosen the locking screw that secures the ballnut mount at this time. Once the motor mount is tight, turn the ballcsrew by hand, until the saddle is all the way forward. Now snug up the locking screw that secures the ballnut mount. Done.
Install the X-axis ballscrew as shown in this photo. Note that the ballnut is on the right hand side of the mill. Re-install the table. Do not tighten the gibs yet, leave them loose. Slide the table to the left so that the ballscrew is sticking out the right hand side. Slide the original thrust bearing plate from the hand wheel onto the end of the ballscrew. Put the locking collar onto the end of the ballscrew, push it hard against the thrust bearings, and tighten. Slide the table against the thrust bearing plate, and tighten it in place with two 6mm cap screws. Install the motor coupling on the left hand end of the ballscrew. Install the X-axis motor mount on the left hand end of the table. Snug up the set screws that held the original brass nut in place, not tight, just snug. Done, ready for tweaking.
Remove the Z-axis fine feed, spoked handle, and the splined shaft the engages the rack. Use the Z gib lock to make sure the head doesn't slide down the column, and remove torsion arm, or gas spring depending on which type of counter-weight your mill has. Remove the plastic stop at the top of the column, its what keeps the head from coming off the column. Now lift the spindle head until it is in THIS position.
Slide the head down SLOWLY, until the Z-axis motor mount is resting on the top of the column. Now use the screw that held the platic stop at the top of the column to secure the Z-axis motor mount.
You now need to drill two holes in the column to finish securing the Z-axis motor mount. You have two options, ONE: drill 1/4" holes and use the 6mm nuts and cap screws, or TWO: drill and tap the two hole with a 6mm tap. Its your choice. I chose to tap the holes, it looks a little cleaner, and a 6mm tap is only a couple dollars.
With the motor mounts all in place, its time to mount your motors & tighten couplings.
Run the X table back and forth until you feel there is no binding, then tighten everyting down. Repeat this step with the Y, and then the Z axis. For the Z axis, you will need to remove the three 6mm screws in the column and lift the head so you can tighten the 12mm screw from inside the head.