Great idea on bike spokes.
I use drill rod, which can be had in many diameters. Same sizes as number drills, and fractional sizes by sixty fourths in the smaller sizes.
If I drill with a 5/64 drill(.078), and the hole is too loose or too tight, I have the option of the pin sizes below. This is precision ground rod, easy to cut, and can be hardened if you like. They will never mushroom once hardened.
Drill rod can be had in .075, .077, .079, and .081
5/64 is more substantial than 1/16, and easy to tap in and out with a 1/16 drift without chewing up the wood. I round the pin ends to prevent the pin from cutting the hole bigger.