In this instalment we are going to add the Z-carriage assembly.  It is similar to the previous two assemblies, but instead of the basic shaft supports we will be using pillow block supports.


Z Carriage Components

The Z-Carriage consists of a Z-Carriage Plate, two 16” 8mm shafts, four 8mm sliding bearing trucks, and four 8mm pillow block shaft supports.

The Z-Carriage plate is supported by the two shafts and four bearing trucks, while the 8mm pillow blocks are used to secure the shafts to the X-Carriage. As with the previous carriages, I had to find the sweet spot for the distance between the two trucks.  The further apart they are the more rigid your table will be. The down side is that you lose travel.

The trucks on the Z-Carriage are 4-1/4" from outer edge to outer edge. The shafts are 2" apart. This will yield 3" of Z travel.

Z Carriage Components


Z Carriage Hardware

In addition to the carriage components listed above, the following hardware fasteners were used to secure the Z-Carriage plate to the bearing trucks and the pillow blocks to the X-Carriage plate:

  • 16, 4mm x 16mm machine screws
  • 16, #8 washers
  • 16, #8 lock washers
  • 8, #10-24 x 1-1/4 machine screws
  • 8, #10-24 hex nuts
  • 8, #10 washers
  • 8, #10 lock washer

Please note that I used #8 washers for the 4mm machine screws.  This is only because they are cheaper and easier to find than their 4mm counterparts.



The first step is to install the pillow block shaft supports, as shown in Figure 2. The supports are held in place with two #10-24 x 1-1/4" machine screws.

The screws are secured (Figure 3) with a #19 washer, #6 washer, #10 lock washer, and finally a #10-24 x 1-1/4” hex nut. At this point the nuts should only be finger tight. The shaft supports should look like the ones shown in Figure 4.


Next, the shafts are inserted through the upper pillow blocks, and two 8mm trucks are added, as shown in Figure 5.

The shafts are pushed through to the lower pillow blocks and secured with the set screws on the shaft supports, as shown in Figure 6.  The bottom of the shaft should be flush with the bottom side of the lower pillow blocks.  Don’t worry about the excess shaft that is sticking out above the upper pillow blocks.  Later you will install a motor mount to the shafts.


The Z-Carriage plate should be created from a piece of 3/4" stock. I recommend melamine coated particle board. The plate has four holes for each truck and two holes in the middle to mount the ACME nut. Several additional holes were added for attaching the spindle mounts. The truck and ACME nut holes have a 3/8” pocket so that the heads of the hardware won’t interfere with the spindle (Figure 7).

Two square recesses were added to the rear side of the Z-Carriage plate. These allow the plate to clear the lower pillow blocks. (figure 8)

The plate is secured to the four trucks with 16, 4mm x 16mm machine screws. A #8 washer/lock washer combo is also added, as shown in Figure 9.



Once the carriage plate is secured to the four trucks, move it all the way to the top and tighten the screws on the upper pillow blocks. Next, move the carriage plate to the bottom and do the same with the lower pillow blocks. Once you are happy with the movement of the carriage, tighten all the nuts. 

This completes the KReduCNC Z-Carriage assembly. As stated earlier, the excess shaft lengths on the top of the Z-Carriage will be used to support the Z motor mount and later to secure hoses and/or cables.


Drawing Files

The drawing files for the Z carriage can be found here:

KReduCNC Z-Carriage Drawing Files

Please note that these files are subject to change. You will need some sort of CAD software that can import eps or pdf files to use them.  They are raw 2D drawing files without annotations.



Please note that there are cheaper linear motion components available. These are the ones I used. Almost all shafts and supports will works, but don't cheap out on the bearing trucks, as you get what you pay for. 


Upgrade Update 11/19/2018

I am constantly changing the spindle mounts so I can experiment different spindles and accessories.

The melamine coated particle has just not held up. So today I upgraded to some 1/2" Corian, which I picked up from a local thrift store for a couple bucks.

It is built exactly like its particle board coutnerpart, but since its only 1/2" thick the pockets for the screws are only deep enough to keep the screw heads recessed.

I used .185" deep pockets.

Note that you also need to add a couple pockets on the reverse side to allow clearance over the lower pillow block supports.

First the front is cut.

You can make the carriage by hand using a drill press or, if your KReduCNC is up and running, you and can machine it.  Just make sure you take light cuts.

As before I am using my KRMx02 CNC to make the carriage.

If you decide to make it with a drill press, drill the pockets first, then the through holes.


Next the rear is cut.

Two pockets are added to the rear of the plate to clear the two lower pillow support blocks.

These can be done manually with a drill press by makeing multiple cuts, then cleaning the slots with a rotary tool.  They don't have to be pretty, they just have to clear the pillow blocks.

The plate is assembled with the same hardware listed above.

Here is a set of drawings showing the rear slots.

Z Carriage with Slots