Working with small engines (especially vintage watches and clocks) require (amongst others) crisp, precision ground screwdrivers.
This instructable will help you create a tool for repeatedly grind perfect screwdriver tips. The idea is to roll the tool on the bearings back and forth, over an abrassive media, to grind the tip.
These screwdrivers have removable tips made of brass and sometimes copper ( for not marking or scoring the screws and also not be affected by magnetism).
There are some branded similar tools in the market that use a spring instead of a screw but cost quite a lot of money.
This tool costs just a fraction of the branded ones and can have the same results.
Hope you like it and vote it ?
This is a small video of the tool in action.

Lets get started

Step 1: Tools

No special tools needed. A pillar drill would help drilling and tapping square holes, but you can get away with a steady hand and an electric drill.
Also a 4mm tap with a taping wrench and a small file.

Step 2: Materials

The list of material is pretty straight foreward and simple.
- 2 identical ball bearings with 8mm ID (i used an old pair i replaced from my small bandsaw)
- An 8mm round steel rod about 6cm long
- A 4mm 3cm long screwdriver sloted machine screw
- Some loctite or epoxy or even superglue.

Step 3: Drill a Center Hole

Use a file to create a flat spot on the rod. Start with a small stuby bit and progress to 5mm. That leaves 1.5mm on each side.

Step 4: The Side Retaining Screw

This is a critical part. Find the center of the rod (not like mine :) ) , drill until you go through the center hole, countersink and tap.

Step 5: Assembly

Assembly time. Place the bearings on either side of rod, epoxy them in place and leave to set.

Step 6: Finished Tool and Use

Thats it. Place the small retaining screw on. It will retain the screwdriver in place while grinding. The distance the tip protrudes from the tool defines the tip angle. Use your favorite sharpening stone or emery paper. Start gently on one side. To grind the other side, just flick the tool the other way. Continue until you get an even grind on both sides. Remove the screwdriver from the tool and enjoy. If you create a sharp edge, just knok it off.

Step 7: Through the Lens and Extra Tip

This is the result as seen from a magnifying glass. And an extra tip. Mark the screwdriver so the next time you use the tool, you keep the same distance, thus the same angle.
Thats it. Hope it is usefull to any or all of you. Any comments are welcome.