When You Need Accurate Holes in a PCB, Only a "Ridiculously Complicated" MIni Drill Press Will Do
Over a decade in the making — though shelved for the majority of the time — this live-view "part logic, part analog" hole-maker delivers.
Pseudonymous EPOS engineer and maker "throbscottle" needed to drill a few holes in PCBs — so did the sensible thing and spent around three years over a 10-year period building and tinkering with a self-described "ridiculously complicated" auto-feeding mini drill press.
"I built this PCB drill to do precise work with tungsten carbide bits,, which are notoriously fragile, and are intended be used in a CNC [Computer Numeric Control] drill," throbscottle explains. "I didn't want CNC. I just wanted a precise drill where I can position the work with both hands and operate the drill with my foot. I also didn't want to program a microcontroller just to run a drill up and down, since needing to learn how to program it first seemed rather excessive (back when I drafted the first design). So I started looking at analog motor control. What I ended up with is part logic, part analog. A bit like Robocop."
The maker began the project in 2014, more than a decade ago, though it spent around seven years on a shelf before being rediscovered and finalized. The drill is operated via either a push-button or a foot switch, and is designed for precision: while an initial prototype used laser targeting with less-than-ideal results, the finished design uses a low-cost borescope camera to provide a live view with overlaid crosshair image. "With perspective correction, this works well," throbscottle says.
"Mechanically speaking, a much superior version of this drill could be built by adopting the mechanism used in pillar drills (or press drills, if you like)," throbscottle admits. "Much too late, I realised the vertical movement would be better driven using a servo. By then I already had a working prototype, and wasn't going to change the design. Using a stepper motor would eliminate the need for feedback, unfortunately I hadn't realised this when I did the initial design. A stepper also needs precise digital control to ensure the correct number of steps are always generated. So another alternative to consider, but you may need a microcontroller for this."
"I had settled for a system that's 'pretty good' instead of 'perfect' due to aesthetics, despite the extra complexity and vibration issues," throbscottle concludes of the finished build. "Eventually I decided that having a consistently behaving drill to be more important."
The project is detailed in full, including a parts list and a schematic built around a 74HC74 flip-flop chip, on Instructables; "The availability of some of the parts I used may have changed by now," throbscottle warns, "so you might need to make substitutions."