[cemented carbide drill] instructions for machining deep holes

More and more processing workshops are using integral cemented carbide bits instead of gun drills to process deep holes. It is considered that the performance advantages of this kind of drill are becoming more and more attractive to manufacturers who process deep holes with gun drill on their own lathe or subcontract the deep hole processing task to gun drill processing workshop. However, compared with gun drills, which usually use cemented carbide or hardened high-speed steel drill tips, hardened steel shank and straight groove, monolithic cemented carbide deep hole drills also have some limitations. For example, their drilling depth limit (dimensioning) is 40 times the aperture, while gun drills can easily drill deep holes with a depth of more than 50 times the aperture.

Gun drill can drill and process all kinds of difficult machining materials. "Because the processing speed of gun drill is slow, it is easier to remove chips. Chip removal is a big problem when drilling titanium alloy and stainless steel, and gun drill has better versatility when processing difficult machining materials. Gun drill will still be widely used in these processes."

Another obstacle to the use of cemented carbide deep hole drill is that the machining personnel are worried about its brittleness and the potential risk of fracture. For example, a manufacturer is worried that with an integral cemented carbide bit with a diameter of 6.35mm, it can drill 240mm deep holes in an extremely difficult alloy material such as nitronic 50 Nitrogen Strengthened austenitic stainless steel in less than 4 minutes, while the bit can still remain intact. The person in charge of the factory first clamped a standard length cemented carbide bit on the lathe, drilled a guide hole twice the hole depth (about 13mm), and cooled the whole cemented carbide bit (diameter 6.35mm, length 30 times the diameter) in rt100t for drilling. He said, "after I switched to use it, I compiled an M00 code. Then I used the high-pressure nozzle of the lathe cooling system to provide 2000psi and 3.5gpm high-pressure coolant. Due to the high-pressure cooling, a sealed sleeve collet was selected to hold the drill bit. When the drill bit was drilled into the hole, the high-pressure cooling nozzle was turned on." Cutting parameters: circumferential cutting speed 42m / min (140sfm), spindle speed 2140r / min and feed rate 0.089mm/r. The processing time for drilling each hole (including drilling guide holes) is about 3.5 minutes. A total of 65 holes were machined before the drill had to be reground and recoated (TiAlN coating).

From the perspective of productivity, the processing efficiency of integral cemented carbide bit is 8 times higher than that of gun drill; From the perspective of processing cost, the processing workshop saves the labor cost and transportation cost of outsourcing processing. Although the overall price of cemented carbide bits ($375) is more than five times higher than that of gun drills ($70), the significant increase in productivity can soon offset and exceed the increase in tool costs.