PM-25MV Mill Conversion

Note: This is a work in progress. I’ll likely be updating the designs of the 3D printed parts and adding/updating features.


3D Models on Thingiverse ›

Ballscrews & Bearings

Here’s is Franco’s overview. In the description of this video on YouTube is a link to an excellent interactive 3D model of his PM-25MV conversion that I’ve found myself referring to many, many times during my conversion.

Definitely subscribe to Franco and watch all his PM-25MV conversion videos if you haven’t already.
I bought Chai’s ballscrews & ballnuts off E-Bay:

And then I straightened Chai’s ballscrews:

Here are the angular contact bearings I bought:

The FK bearings are pre-loaded, so (I guess?) you don’t need to worry about over/under-tightening the lock nut that holds them in place.

Screws, Nuts. Washers

Buy an assortment of m4 and m5 screws/nuts/washers on AliExpress including:

  • 3 90mm m5 screws to attach z motor mount together
  • 4 60mm m5 screws to attach z ballnut to ballnut holder
  • 4 20mm m5 screws to attach z motor mount to mill
  • 4 30mm m5 screws to attach z motor to motor mount
  • 2 50mm m3 screws to attach x ballnut to ballnut holder (Or 2 50mm m4 screws? I think I redisigned the x ballnut holder for m3 because I didn't have 50mm m4.)
  • 2 35mm m4 screws to attach y ballnut to ballnut holder
  • An assortment of m4 screws of sizes <= 25mm (25, 20, 16, 14, 12) to attach FK bearings to plastic parts.
  • m5 nuts
  • m4 nuts
  • An assortment of m3, m4, m5 washers (helps prevent the screws from digging into the plastic parts)

It wouldn’t surprise me if I’ve forgotten some screws or got some lengths wrong.. You can always cut a long screw down to make a smaller one in a pinch so it might be a good idea to get a few extra long m4 and m5 screws just in case. Perhaps some long m3 screws too.


Here are the motors, drivers, and power supplies I purchased:

Here is my (mostly completed) electronics enclosure:

It’d probably be best to buy an enclosure with a PLASTIC backplate. Or make your own backplate. Drilling and tapping holes in the metal backplate sucked. Not to mention 3d printing custom plastic stand-offs for everything in it.

Using spade connectors on the wires screwed to the bus bars also would have been smart. (I didn’t.)

Motor Mounts, Ballnut Holders

You can download Franco’s parts here.

My 3d Printable models are at:
Overview of externally visible 3d printed parts:

Videos of the internal parts (ballnut holders) are in the build log below.

Y Axis Build

Y axis ballscrew holder design:

I forgot to mention in this video that I filled the void between the metal and epoxy parts with epoxy.

Y axis install:

Y axis motor mounted:

X Axis Build

Dealing with clearance issues:

Minor hiccup:

Aligning X axis:

More alignment of X axis:

YAY! X & Y are moving!:

Z Axis Build

Removed the original Z axis screw:

(Ignore the bit at the end about the ballnut holder – it broke.)

Another soon-to-fail Z ballnut attempt:

Installation of Z axis motor mount:

Broke the Z axis ballnut holder:

New Z axis ballnut holder:

Z axis head removal:

I found a way to manually turn the Z ballscrew!:

Yay! Z Axis finished!: