Schrader tubes in Presta configured Rims? My 26" mtb rims support presta sized tube stems, however can I drill the diameter of the holes in the rims bigger in order to support Schrader stemmed tubes? what is the proper way to do this, is there a kit?
In case you really want to drill, the only thing you need is a 10mm drill bit, and a sandpaper to give a smooth finish.

It is true that the rim gets weaker, and very narrow rims should not be drilled, but I have performed this enlargement a couple of times and rode the wheels some honest hundreds of km in every kind of terrain, with no problem.

I did this because I like the ease to get at any gas pump to top tire pressure after trails, and also because schraeder tubes are more avaliable and less expensive where I live.