It was always difficult for me to sharpen a drill with a diameter of less than 3 mm. Most of the available tools for sharpening drills are not designed for this, and manual sharpening was not always obtained. Sharpening drills with a diameter of less than 1 mm did not work at all.

Once I came across a description of a little-known tool Wishbone for sharpening small drills and I decided to do something similar, but suitable for manufacturing on an FDM printer. The result is Wishbone 2. This tool allows you to quickly and efficiently sharpen drills with a diameter of 4 mm to 0.5 mm without any special skill.

Made using 3D printing on an FDM printer, easy to assemble, inexpensive.

The work of Wishbone 2 is shown in the video: https://youtu.be/7oEiV30UQRUAssembly instructions are in the PDF document.

Project page: https://3dladnik.wixsite.com/workshop/wishbon-2

P.S.The angle of sharpening ϕ1 at the apex can be changed simply by changing the offset of the drill. Preservation of symmetry is ensured by an equal number of passes on the abrasive, or corrected by additional passes. It is better to control the quality of sharpening small drills with optics.

The rear cutting angle α is set “by eye”, with sufficient accuracy, it is not difficult, it can be estimated as follows:

1 - take a matchbox, place it vertically, on a narrow long edge,2 - put the school protractor to a short edge and notice how it looks at the same time,3 - tilt the box to the right by 5 degrees, mark the difference with the previous position,4 - now tilt the box to the right 40 degrees

• A tilt of 5 to 17 degrees provides a rear cutting angle α
• A slope of 25 to 40 degrees provides a second angle

From my own experience, the rear angle α is obtained with a deviation of +/- 2 degrees, which is quite enough.