Root-Cause

Scrap in deep hole drilling is more expensive than scrap in most other machining operations. By the time the hole is drilled, the part has already been turned, heat-treated, and faced. A scrapped bore means all that upstream work is lost. I have worked on reducing scrap rates across multiple shops. The approach that works is not complex — it is systematic. Track What You Are Scrapping The first step in reducing scrap is knowing what you are scrapping and why. Without data, you are guessing. ...

Why Root Cause Analysis Matters Root cause analysis (RCA) is the difference between fixing a problem once and fixing it over and over. I have seen the same broken drill, the same oversized hole, and the same surface finish problem recur because someone fixed the symptom instead of the cause. A symptom is what you see. A broken drill is a symptom. The root cause is why the drill broke. Fixing the symptom means putting in a new drill. Finding and fixing the root cause means the new drill does not break again. ...

I examine every broken gun drill to figure out what went wrong. A broken drill is not trash — it is evidence. The break pattern, the fracture surface, and the location of the break all tell you something about the cause. I have learned more about deep hole drilling from examining broken tools than from any textbook. Problem Description Gun drills break for many reasons, but the break itself is the end result of a chain of events. The drill does not snap spontaneously. Something causes the load to exceed the strength of the drill body. The break pattern preserves information about what that something was. ...

I have been diagnosing gun drill breakages for over a decade now, and I can tell you one thing for certain: a broken gun drill is almost never a single-cause failure. It is a chain of events that lines up in the wrong order. But certain root causes show up again and again. Tool breakage is one of the most expensive problems in deep hole drilling. A single broken drill can mean a scrapped part, a stuck tool removal job, and days of downtime. Here are the ten most common causes I have seen, ranked by how often they show up in my shop. ...

Why Intermittent Problems Are Different I have spent more hours than I care to count standing at a machine, waiting for an intermittent problem to reappear. The part that makes these issues so frustrating is obvious: if the fault fired every cycle, I could isolate it in an afternoon. But when a tool burns up on one part, runs fine for the next ten, and then burns up again on part twelve, you are no longer troubleshooting a single event. You are chasing a condition that crosses some invisible threshold only part of the time. ...