for fine-grained sandstone the wear rate is 10 mg/sec (temperature produce during drilling is around 128 dec. centigrade)

and Medium-grained sandstone the wear rate is 6.66 mg/sec (temperature produce during drilling is around 91 dec. centigrade)

my question is what is the main role between these two sandstone. (whether pore space leads to decrease the temperature and wear rate of the drill bit when we used for the medium-grained sandstone) please give the reason for the same sir.