A gundrill or BTA head that snaps deep in a bore is not automatically a scrapped part. With the right approach — know where it broke, open a path from the back, then EDM or spade-drill the shank — most parts can be saved in an afternoon.
Before touching anything, find out where the tool broke and why. Boroscope the bore. A break near the entry is a setup problem (alignment, bushing, chip jam); a break deep in the bore is usually a chip-pack, a dull edge, or a whip problem. The recovery method depends on the position:
| Break location | Likely cause | Best recovery |
|---|---|---|
| At entry / within 5×D | Misalignment, bad pilot, bushing wear | Push out from the back, or EDM |
| Mid-bore | Chip pack, coolant loss, dull edge | EDM the shank, or reverse drill |
| Near the bottom | Feed/breakthrough, whip | EDM; re-pilot and continue |
If the tool broke through or near the end, machine the other end open and push the shank out with a drift. Cheapest and fastest.
Burn the broken shank away with an EDM electrode fed down the bore. Works on any material including hardened; leaves the bore wall intact if you stay centered.
Feed a stub spade drill down the broken tool’s coolant hole or flute to break it up, then fish out the pieces.
Drill a small reverse-twist hole into the shank and use a screw extractor. Only works on ductile shanks with accessible ends.
Loosen wedged carbide with ultrasonic vibration applied to the shank through a rod.