His name was Frank, and he had been running deep hole drilling machines since before I was born. Frank retired in 2018 after forty-two years in the trade. He had started on manual machines in the 70s, drilling oil field components, and had seen the transition to CNC, to BTA systems, to everything we use today. When he walked away from the trade, he took forty-two years of knowledge with him.

I met Frank about a year before he retired. I was struggling with a job. A batch of stainless steel shafts, 316 grade, needed 20mm holes drilled 400mm deep. The machine was running but the surface finish was inconsistent. One part would come out at Ra 0.6, the next at Ra 1.2, and then the third would be back down. I could not figure out what was changing between parts.

Frank walked past my machine, looked at the pile of chips on the conveyor for about three seconds, and said, “Your coolant concentration is too high.”

I stared at him. “How can you tell that from looking at the chips?”

He picked up a handful of chips from the conveyor and held them out. “See how the edges are feathered? That is from lubricity being too high. The chip is sliding over the cutting edge instead of shearing cleanly. Back the concentration down to about six percent and your finish will even out.”

I checked the coolant concentration with a refractometer. It was at 9.5 percent. I diluted it to 6 percent. The next part had a consistent Ra 0.7 finish and stayed there for the rest of the batch.

That got my attention. I asked Frank if he would show me what he looked at when he read chips. He spent the next two hours with me, standing in front of the machine, picking chips off the conveyor and explaining what each one meant.

“Short and curled means you are cutting properly,” he said. “The chip should break into segments about three to five times the feed per revolution. If the segments are too long, your feed is too low or your chip breaker is wrong.”

He picked up a chip that was long and stringy. “This means you are rubbing, not cutting. The material is being pushed aside instead of sheared. You get work hardening, poor finish, and short tool life. Increase the feed or check the edge sharpness.”

Then he showed me a chip that was almost powder. “Fine dust is bad. It means the chip is being re- cut because it is not clearing the hole. Check your coolant pressure and your peck cycle.”

He pulled a chip that had a blue tint. “Blue means heat. If the chip comes out blue, your cutting speed is too high or your coolant is not reaching the cutting edge. Blue chips lead to built-up edge and tool failure.”

We looked at chips with different edge conditions, different curl patterns, different thicknesses. He showed me how a chip that was thicker than the feed per revolution meant the material was swelling ahead of the cut, which indicated a dull tool. He showed me how a chip with a ragged edge meant the cutting edge was chipped.

After that afternoon, I started looking at chips the way Frank did. Every time I picked up a chip from the conveyor, I asked myself what it was telling me. The color, the shape, the thickness, the edge condition. It all meant something.

Frank retired about a year later and I have not seen him since. But every time I stand in front of a machine and look at the chips coming out of a hole, I think about that afternoon. He took a skill that had taken him four decades to develop and compressed it into a couple of hours for me.

These days I try to pass it on to the younger guys. When I see somebody staring at a machine, confused about why a part is not coming out right, I walk over and pick up a chip. “What is this trying to tell you?” I ask.

Most of the time, they look at me the same way I looked at Frank. But the ones who pay attention start seeing the machine in a completely different way. Chips do not lie. They tell you exactly what is happening inside the hole, if you know how to read them.