scrader valve

[kurtallen46gp2009]

i want to fit scrader  valve tubes on my ukai wheels but the holes are to small to fit the valve through .
what size drill bit do i use ?

[oldtired]

could  be out on this so double check         5/16ths   or roughly 8mm  think its about 7.9mm  so 8mm  should be ok ,  schwable still do 20inch presta valve tubes though 

[kurtallen46gp2009]

thanks