I'm in my first year and while I'd say i've gotten a decent hang of drilling, I always end up with either my buccal or lingual walls being perfectly convergent and the other being divergent or just straight (usually straight). It depends on the quadrant that i'm working on whether it's my buccal or lingual that's not convergent but always one of them isn't. I've talked to my prof about it and i've been told that the reason is due to not angling my bur towards the long axis of the tooth. I have drilled probably hundreds of preps and in my eyes, it seems as though i am drilling towards the long axis, but every single time, I am still left with one of my walls not being convergent. To drill, i usually use the 330 on high speed for my initial outline, then i'll take my 245 on slow and refine everything. Does anyone have any tips on angling your bur towards the long axis of the tooth/finding the correct long axis of the tooth?