Maybe this was so obvious the author did not write it down, but you can also use this to measure accurately weight of objects below 10 g.
First you make the stacks for 15.0, 15.5, .. 17.5, 18.0. Preferrably using tiny amounts of superglue.
Then you put one stack on one side of the scales, and the other stack on the other side, and you have accurate weights for 0.5, 1.0, 1.5, 2.0, 2.5, 3.0.
You can make some of these combinations more efficiently, but the more coins you use in total, the better accuracy you get as manufacturing variations average out (up to a certain point of course).
It is a bit more cumbersome to make a quarter gram, but you can make one stack of {5x 0.01, 2x 0.02, 1x 0.1, 1x 0.2} for a weight of 27.46 g, and one stack of {2x 0.02, 3x 0.05, 1x 0.01, 1x 0.2,} giving 27.72 g, for a difference of 0.26 g.
As others have mentioned, using Lego is a nice way to make high precision scales. Take a 1x16 Lego Technic brick with holes and balance it on a thick needle through the middle hole. Needle support can be built from other bricks. Use thin sewing thread and some bricks to hang some 6x8 plates from each end.
First you make the stacks for 15.0, 15.5, .. 17.5, 18.0. Preferrably using tiny amounts of superglue.
Then you put one stack on one side of the scales, and the other stack on the other side, and you have accurate weights for 0.5, 1.0, 1.5, 2.0, 2.5, 3.0.
You can make some of these combinations more efficiently, but the more coins you use in total, the better accuracy you get as manufacturing variations average out (up to a certain point of course).
It is a bit more cumbersome to make a quarter gram, but you can make one stack of {5x 0.01, 2x 0.02, 1x 0.1, 1x 0.2} for a weight of 27.46 g, and one stack of {2x 0.02, 3x 0.05, 1x 0.01, 1x 0.2,} giving 27.72 g, for a difference of 0.26 g.
As others have mentioned, using Lego is a nice way to make high precision scales. Take a 1x16 Lego Technic brick with holes and balance it on a thick needle through the middle hole. Needle support can be built from other bricks. Use thin sewing thread and some bricks to hang some 6x8 plates from each end.