Improved Small Electric Screwdriver (Version 2)

After a few years of using my first version of a mini electric screwdriver, one of the buttons finally broke. That was the moment I decided to stop saying “I’ll redesign it tomorrow” and actually build an improved version.

The main difference compared to the previous model is the power supply. This version does not have a built-in charger. Instead, it uses a standard 18650 3.7V battery, which can be easily removed and charged externally or replaced with a fully charged one. For me, this is a big advantage.

Another improvement is the button placement. The buttons are positioned slightly deeper inside the case, so when the screwdriver is rolling around in a drawer, they don’t get pressed accidentally — something that often happened with the first version.

One downside is that the screwdriver rotates a bit slowly because it runs on 3.7V. I think it would perform better at around 5V. For Version 3, I’m planning to add a boost converter to increase the voltage and achieve higher rotation speed.

Components Used

1. DC Motor – 5V, 60 RPM
2. No-load current: 50 mA
3. No-load speed: 60 RPM
4. Suitable voltage: DC 3V – 12V
5. Speed range: 36 RPM – 108 RPM
6. Shaft diameter: 3 mm (D-shaft, 2.5 mm)
7. Mini Micro Limit Switch (NO / NC, 3 pins)
8. 18650 Li-ion Battery – 3.7V
9. Spring (taken from a larger pen)
10. Ball bearing
11. Outer diameter: 15 mm
12. Inner diameter: 5 mm
13. Thickness: 5 mm
14. (most likely from a fidget spinner)
15. Piece of metal strip for lithium-ion battery connection
16. (can be replaced with any cut conductive metal, even from a beer can)
17. 4 small screws
18. Length: 16 mm
19. Diameter: 1 mm
20. (I could only find 3 of this size, which took the most time to locate and fasten without breaking anything)
21. Small screwdriver bit holder
22. Shaft diameter: 5 mm
23. (taken from an old broken screwdriver)
24. Brass Rigid Motor Shaft Coupling
25. Size: 3.17 mm – 5 mm
26. Used as motor transmission connector

Here are a few important details that are not obvious from the photos but are essential for proper assembly and reliable operation.

1. I used super glue (cyanoacrylate) to fix the buttons in place. This prevents them from moving or shifting during use.
2. The same super glue was also used to secure the metal strip that carries the negative (–) contact from the back of the battery to the circuit.
3. The spring inside the battery cap is fixed using hot glue. This keeps the spring firmly in place and prevents unwanted movement.
4. The metal contact plate is bent over the negative terminal, and the spring presses it firmly against the battery pole. This ensures a stable and reliable electrical connection even if the battery is removed and reinserted multiple times.

These small details greatly improve the durability and reliability of the screwdriver.

Solder the negative wire to the metal strip, orienting it toward the plastic. Adjust the wire so it fits neatly in the channel, allowing the battery to slide smoothly into the cylinder.

Before you start, check that you have the correct 4 screws. Finding them was the biggest challenge for me, and I would have redesigned the case for larger screws if it hadn’t already been printed. As you can see, it didn’t turn out perfectly — the screws almost came through the other side.

You can check out the first version of this project here:

https://www.instructables.com/Mini-Screwdriver/

This project was inspired by the following video:

https://www.youtube.com/watch?v=ZXD2Jqg4518&list=PLb3RPerjHjoqlx4x_Au4Av_AHAGOlWhZE&index=3