It's time to attach the 1/2" 5-start ACME lead screw and nut to the CNC. 

One of the problems with any type of screw system for use with CNC machines is that as the lengths get longer, they tend to whip at high speeds. Here I will be using 36" screws, so I shouldnt have any problems.

Adapter Plates

The Y drive system consists of two bearing mount plates, two motor mount plates, two drive plates, and two bearing cover plates.

While my eventual target will be 1/4" - 1/2" Aluminum (or possibly steel). These were done in 1/2" Corian.

 

Motor Mount Assembly

First I installed the motor mounts on the rear of the machine frame, as shown here.

Note that I added extra length so that the plate not only attaches to the end of the base side extrusion, they can also attach to the front and rear extrusions using T-nuts.

This would add even more support to the base.  Im not sure these are needed as the double corner brackets on the inside does a pretty good job at keeping things rigid. I may remove these in time.

The motor is then attached to the mount.

A helical coupler is then added to the motor.

 

Bearing Mount Assembly

The bearing mount adapter plates are installed on the front of the machine.

The bearing mount plate has a pocket that holds a 1/2" bearing.

At some point I will look into adding thrust bearings as well. For now this setup has proven to work very well.

A bearing cover is added to hold the bearing in place.

Update

Note the pocket in the cover.  This is a new design that will eventually replace the pocket in the actual bearing mount.

The adapter plates are very easy to make by hand. The bearing pockets however, require a little more precision. By moving them to the covers, I can fabricate these parts for those that don't have a way of doing so.

 

ACME Screw and Nut Assembly

A drive plate is added to the Y carriage.

A 5-start 1/2" ACME nut is installed on the drive plate.

A 5-start 1/2" ACME screw through the bearing, into the nut, and then into the coupler.

The bearing needs to capture the screw to remove lateral movement due to the helical coupler.

 

 

Conclusion

With both Y drives installed. Its time to move on to the X drive.