It was the kind of call every deep hole drilling shop dreads. The customer’s operator had pushed the cycle start button, walked away, and come back to a machine that had stopped mid-cut. The alarm said tool breakage. The part was a forged steel component — think crankshaft oil passage, hydraulic cylinder, or similar — worth more than the drill that had just snapped inside it. And the machine had stopped with the broken drill about 400mm down a 500mm-deep hole.
Scrapping the part meant replacing a forging that took weeks to obtain. Fishing the drill out wrong would wreck the hole and cost the part anyway. The operator was staring at a choice between weeks of lost production and an expensive gamble.
What actually happened next is a process, not a trick. Here’s how it works.
Step 1: Know Exactly Where You’re Working
Before anything goes in the hole, we have to know what’s in there. Our engineer started by getting the operator to measure the depth of the break and report the condition of the coolant return — is the pump seeing normal pressure, or is the flow partially blocked?
Two things matter at this stage:
- The position of the break. How far down is the broken tool? The deeper it is, the more careful the extraction has to be — you are working blind, with very little clearance between the tool and the hole wall.
- The posture of the broken piece. Is it sitting roughly centered, or has it cocked sideways in the hole? A tool wedged at an angle behaves completely differently from one that’s free.
The machine’s own axis data and a simple depth check from the operator usually answered this well enough to plan the extraction.
Step 2: Understand What You’re Pulling On
This is where the physics matters, and where operators often make the fatal mistake.
A gun drill is not a twist drill. For deep drilling it is a long, slender tool — a brazed carbide cutting head on a steel shank. Two things follow:
- It won’t respond to a magnet. The cutting head is solid carbide, which is not magnetic. You cannot lower a magnet and pull it out. People try this, and it fails — worst of all, a magnet can’t even feel how the tool is seated, so it gives you no feedback.
- It will not come out by force. The broken tool is wedged in a hole that is barely bigger than it is. Pulling hard on whatever you can grab will either shear the extraction tool, or — worse — drag the broken drill sideways and score the hole wall beyond repair.
The rule: extraction is a slow, controlled process, not a pull. The goal is to grip the broken tool and work it free with a combination of gentle tension, rotation, and coolant, never transmitting force to the bore wall.
Step 3: Choose the Right Tool
Depending on what the break looks like, one of two approaches applies:
- If the broken shank is steel and reasonably accessible, we drill a small pilot into the broken tool’s shank from above, tap it, and thread in a screw extractor. The extractor bites into the shank, and we rotate it out — like backing out a stripped screw, but at 400mm depth.
- If the broken piece is too short, too hard, or sitting at an angle, we use a sleeve-type extractor: a thin-walled collar that drops over the broken tool, is drawn down over it, and grips it from the outside by friction. This is the gentler method for a carbide head, which cannot be drilled and tapped.
Whichever tool is used, it goes down on a rigid, controllable holder — not a flexible wire. We need to feel what the tool is doing at the other end, which means the extractor has to be driven by the machine’s spindle or a rigid hand-held fixture, with continuous coolant to keep everything lubricated and to flush away any debris.
Step 4: Work It Free, Then Work Out Why It Broke
The extraction itself is methodical: gentle rotation, incremental tension, pause, repeat. Progress is measured in millimeters. A skilled operator can feel when the tool is seated firmly in the extractor and when it’s about to come free — and crucially, when to stop pulling and back off to re-approach at a slightly different angle.
In this case, the broken drill came out intact, and the hole was inspected: straightness unaffected, bore wall clean. The part was saved.
Then came the part of the process that prevents a repeat: why did it break in the first place? Our engineer walked through the cut with the customer’s operator:
- Was the feed rate appropriate for the depth? A common cause of mid-hole breakage is a feed that was fine at the start but too aggressive as the drill got deeper and cutting pressure built.
- Was the drill nearing the end of its expected life? Worn gun drills don’t always warn you — they often break without a gradual decline.
- Was chip evacuation clean at that depth? A packed flute will overheat and snap the tool.
The fix was a combination: slightly conservative feed at the deep end of the cut, and a tool-life schedule so the drill was replaced on a count rather than on failure.
What This Means for You
Broken drills happen. Even well-run shops break tools now and then — a material anomaly, a worn guide bushing, a parameter that was fine yesterday and not today. What separates a shop that survives the moment from one that loses the part is a process:
- Don’t improvise. Lowering random tools into a 500mm hole is how holes get ruined. Understand what’s down there first.
- Match the extraction tool to the broken tool. Screw extractors for steel shanks; sleeve extractors for carbide heads. Never a magnet.
- Pull with control, not force. The bore wall is worth more than speed.
- Fix the root cause. Getting the tool out saves today’s part; finding out why it broke saves the next hundred.
We stock the extraction tooling and keep engineers on call for exactly this situation. If you ever have a tool stuck deep in a hole and the part is worth saving, send us the details — this is one of those calls we take at any hour. And if the breakage keeps happening, the tooling and process review is where the real fix usually lives.