Nickel-Alloy

I get more questions about drilling small holes in Inconel 718 than almost any other topic. A recent Practical Machinist thread about drilling 3mm holes 160mm deep in Inconel 718 at HRC 40-45 got over 3,500 views. The user was struggling with drill breakage, centerline deviation, and surface finish. The root cause in that thread was the same one I see most often: coolant pressure at 8 bar (116 psi) when the job needs 100 bar or more. Here is what I have learned about getting this application right. ...

Additive manufacturing is changing how we think about deep hole drilling. Instead of drilling a solid bar to create a hole, additive processes can build the part with the hole already partially formed. But the as-printed surfaces are not suitable for most engineering applications, so post-process drilling is still needed. I have worked with hybrid manufacturing processes that combine additive deposition with subtractive machining in the same machine. The deep hole drilling step comes after the additive build, and it presents unique challenges compared to drilling from wrought material. The approach to selecting a machine for the application becomes more complex when the machine must serve both additive and subtractive functions. ...