What about using something like the cone tips in this set? https://www.amazon.com/Diamond-Grinding-Accessories-Jewelry-Lapidary/dp/B07ZQ8GPVY/ref=sr_1_27?crid=VU9TLQGEDRDE&dchild=1&keywords=rotary+coarse+abrasive+cone+shape&qid=1609579738&s=hi&sprefix=cone+rotary+%2Ctools%2C212&sr=1-27