My Lathe modifications

I converted my HBM 300 DC mini lathe in 2015 to CNC for about 100 $ (without display). I also made some small changes. For each change there is a zip file containing information, pictures and drawings. There are two changes to improve the rigidity (cross slide nut and carriage saddle press boards). Both are easy to do and undo. The result are best described as wow. You should try it!
I initially started threading using a stepper to drive the spindle (only during threading). To make threading available for more lathe owners, I have added spindle sync threading to GRBL Arduino Uno version Arduino Mega version. For the synchronization I added 2 proximity switches at the back of the spindle, one for the index pulse and one for the synchronization. Using only 1 sensor for the index pulse is also possible.

Files and documentation can be downloaded Download
The CAD designs can be opened by (free software) LibreCAD or ProgeCAD
The electronic designs by (free software) Eagle or Kicad

The items marked ** are needed for CNC conversion
The items marked *** are optional for CNC conversion (Stepper controlled threading, knurling, broaching)

• Extending the spindle back to prevent swarf entering the gearbox
• Changing the cross slide nut fixation to increase rigidity
• Changing the carriage saddle press boards to increase rigidity
• Adding carriage gear cover to prevent swarf entering the gears
• ** Adding a stepper to the Z-axis (carriage), in 2020 upgraded to 1.26 Nm Nema23
• ** Adding a stepper to the X-axis (cross slide) , planned to upgrade to 1.26 Nm Nema23
• *** Adding a stepper to the C-axis (spindle)
• ** Connection the steppers to TB6600 drivers
• ** Connecting the TB6600 drivers to the GRBL controller (Arduino)
• Cooling the TB6600 drivers
• Adding wireless communication to the GRBL controller
• Selecting a power supply
• "Quick change" tool holder
• Adding proximity switches for spindle sync threading
• Adding Spindle RPM display