The Compact Faceting Head


I recently finished one of my long term projects that I had in mind for quite some time before I started. Essentially some ideas I had already after I finished my first self built faceting head (described here).

Beside a better quality and reliability this faceting head should fulfill the following requirements:

  • Better stability
    • The joints and connections between the parts should be more firm
    • It should be more "massive" in order to eliminate vibrations
  • Higher accuracy
    • Arm should be fixed and rotations and movements should not allow any play
    • Angle change should happen on an exact perpendicular movement
    • Index wheel and needle should provide solid fitting, stability, and accuracy
  • Small in size
    • As the name indicates the size of the faceting head should stay as small as possible for the least demand of space
  • Good "usability"
    • Fast and accurate change of angle limit
    • Fast and easy change of rotation index
    • Although arm is fixed, a good view on the stone should be possible

All of that I tried to consider in my design here's the video presenting the outcome:

In the following I'd like to share some details that were not part of the video:

Parts used

You might have seen that many of the self designed parts I milled or turned out of aluminium. I simply bought some left overs from a close metal dealer and used my low cost (and self CNC'd) milling machine and lathe to create arbitrary parts. The axis and rods however are steel shafts. Beside that I bought some ready made parts:

  • ER16 Chuck Holder with 10cm shaft
    • Usually used for milling, but a good solution to hold the dop stick. Also allows to hold dop sticks of different diameters. (However, I use 8mm only so far)
  • Graphite Lubricating Brass Bushings
    • These are a nice option for my use case. However, I cut the ring axially once to allow putting pressure on it by a grub screw. This way there's no play.
  • Optical incremental encoder sensor
    • This piece was one of the more expensive parts (EUR 18,-). The nominal resolution for a full rotation is 1000 ticks. However, using the signal edges more intelligently, it does 4000 ticks. This results in a 0.09° accuracy, which is sufficient. Note that I took the idea from the great book of Tom Herbst: Amateur Faceting
  • Arduino Electronics
    • I chose an Arduino Mega 2560 (Just to keep it extensible. A simple Uno would do as well)
    • 20x4 characters LCD display with an I2C middle piece
  • ... and a lot of M4 / M3 screws, nuts, and threaded bars


My Arduino sketch is kept quite simple, altough I invested quite something in performance tuning in order to have a fast reaction time of the display. If you are familiar with C than it shouldn't be hard to understand the code, it's also commented well.

The sketch is available at I used two libraries:

#include <Wire.h> #include <LiquidCrystal_I2C.h>

If they are not already coming with the Arduino IDE, they should be easy to find on the web.

Construction Plans

This time I collected all single files that I used to feed my CNC mill. I used Inkscape (SVG/DXF) and EstlCam to mill. The actual design I did with the great tool Blender.

I did not publish the files (yet) as they are not "polished" by now. Please contact me via email (see here) in case you are interested in having these.

This article is my 16th oldest. It is 574 words long