About Quality Diamond Tools Owned By Duncan & Duncan Incorporated. Quality Diamond Tools (QDT) was established in 2004 and is considered a small business concern with Jim Duncan as its principal owner. Jim has more than 28 years of experience in the drilling industry. Most of his background comes from 23 years spent with the Christensen organization. While there, he consulted and traveled all over the world, spending countless hours with customers in the field in many different drilling situations. He possesses experience in the manufacturing, consulting, sales, and distribution of diamond bits, core barrels, rods, casing, and all the related drilling tools. Because of valuable customer relationships and experience gained with them in the field, QDT exists today to serve you and your drill tool needs. If you have any questions, feel free to give us a call.