Assuming you are not in the US where imperal cutters are the norm I would suggest getting a 6mm collet and then yoi can fit industry standard FC-3 metric cutters with 6mm shank and cutting diameters from 1mm to 6mm in 0.5mm steps and a few other intermediate sizes. You can also get bull nose cutters in this style. They are comparitively cheap as well. You could also use imperial FC-3 cutters with 1/4" shank these go from 1/16" to 1/4" in 1/64" steps but are not quiet so easily available or cheap.
Have a look at page 8 bottom right, the uncoated JL3 Disposables are always a good buy when on offer
Even if you can source 1/8" shank cutters the adaptors are not as secure as a proper collet.
Edited By JasonB on 07/05/2016 18:23:28
Edited By JasonB on 07/05/2016 18:27:17