Which device is used to repair a stripped bolt hole by inserting a coil?

Which device is used to repair a stripped bolt hole by inserting a coil?

• A. Epoxy insert
• B. Dowel pin
• C. Tap
• D. Heli-coil

Answer: (D)

Repairing a stripped bolt hole is about restoring a strong, fresh threaded pathway for the fastener. A helicoil insert does this by providing a new coil-threaded bore that the bolt can grip. The process starts by removing the damaged threads so the hole is clean and round, then using a special tap to cut new internal threads that match the insert. The helicoil is inserted with an installation tool until it sits flush, and the tang at the bottom is broken off so the bolt can be threaded normally. The result is a durable, reusable thread that distributes load along the insert and resists re-stripping better than the original damaged threads. Epoxy inserts are another repair method but rely on filling and hardening material rather than a persistent coil, and dowel pins are for alignment—not thread repair, while a tap is a tool used to cut threads, not the repair device itself.

Repairing a stripped bolt hole is about restoring a strong, fresh threaded pathway for the fastener. A helicoil insert does this by providing a new coil-threaded bore that the bolt can grip. The process starts by removing the damaged threads so the hole is clean and round, then using a special tap to cut new internal threads that match the insert. The helicoil is inserted with an installation tool until it sits flush, and the tang at the bottom is broken off so the bolt can be threaded normally. The result is a durable, reusable thread that distributes load along the insert and resists re-stripping better than the original damaged threads. Epoxy inserts are another repair method but rely on filling and hardening material rather than a persistent coil, and dowel pins are for alignment—not thread repair, while a tap is a tool used to cut threads, not the repair device itself.