Was set a challenge, can I make a disc with a 0.2mm hole in it that is round. First try was using a pin and ground it down to 0.25mm, however the steel was too weak and broke once the hole was made. Found a broken 0.75mm HHS drill and ground a new punch aiming for just under 0.2mm. Due to the radius on the resin wheel used for grinding, it ended up with less than 0.5mm usable before the taper went out of tolerance. This time the tool survived punching a hole and looks like I can go smaller in diameter, but not by much.
The bottom hole in this example is the 0.2mm and the hole above was opened out to 0.5mm trying to get rid of the ragged edge. The shim stock punched is 0.12mm beer can, the application for such a hole is in a pinhole camera with a 25mm focal length. (hole needs to be 0.18mm ideally)
Just something a little different.
