For trimming OEM studs , this is what I've done several times .
1) mark the overall length required + at least one full thread for good measure.
2) run a sacrificial but good lug nut (or any proper pitched free run nut ) down to the mark (to provide a good perpendicular surface you'll use as a guide for a nice straight cut)
3)using a thin 1/16" thick cutoff wheel with a 90° die grinder (or equivalent ) and using the previously installed nut as a guide Cut the stud off accordingly.
4) run the nut down to the hub for now , do not remove the nut yet . Now using 120 grit or so sand paper and a foam block , sand the end of the stud smooth and to a slightly rounded end taking care not to remove anymore thead material than required .
5) now apply some anti-sieize or grease on the end of the stud ( to keep from damaging the nut ) now remove the nut by hand if possible if not use a ratchet working it back & forth on the cutoff area until the threads are clean & straight enough to install and remove a good lug nut by hand . Clean all grease or anti-sieize thoroughly ! ! You DO NOT want any lubricant on studs or Lug nuts you plan to use for the install ! !
Done !
This is a simple and quick process just seems like a lot to type out .
Pointer on keeping the nut in place while cutting off = wrap a little electrical tape on the stud and run the nut up on it a little until it's in place on your mark.
If you jack up a stud and it requires replacement no worries this is a simple process as well , takes less than 2 minutes to replace one . Just ask here and I'll tell ya how I do it .
☆☆Important☆☆
My way stated above is not the only way , but it's worked for me just fine many times .