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

There are two drives on the Y axis.  Each drive requires the adapter plates shown here:

  • Motor Mount Plate
  • Bearing Mount Plate
  • Bearing Holder Plates
  • Y Drive Plate

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 some drop-in T-nuts.

This would add even more support to the base.  I'm 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

I build the bearing mount assembly.  I only finger tighten the nut at this point.

I used 1/4-20 x 2" bolts and hardware.

The assembly is then installed on the machine as shown here.

Note that I did have to TAP the holes in the ends of the extrusion.

I used 1/4-20 x 1" bolts and hardware.


ACME Screw and Nut Assembly

I build the Y drive plate assembly.

Note the spacer between the lead nut bracket and the plate is 1/16" thick. I have added enough play in the holes that this spacer may not be needed.


The assembly is added to the Y carriage as shown.

Note the orientation of the lead nut.  I will be installing the ACME screw from the bearing side (front) so its easyer to install from the rear side of the nut.

I install the 5-start 1/2" x 36" ACME drive screw

I start by inserting it into the rear bearing block.

Once through the block, I insert a thrust bearing set on the shaft then a collar clamp.

I screw the rod through the nut on the plate assembly

Once through the nut, into the helical coupler.

Finally, I add the final thrust bearing and collar.

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




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