Thread Repair

Damaged threads may be reconditioned by drilling out, rethreading and installing a suitable thread insert. General purpose thread repair kits are available commercially.

IMPORTANT: Refer to the kit manufacturer's instructions regarding the size of the drill and tap to be used.
1. Determine the size, pitch and depth of the damaged thread. If necessary, adjust the stop collars on the cutting tool and tap to the required depth.
Fig 1: Drilling & Tapping Damaged Threads
Courtesy of GENERAL MOTORS CORP.
2. Drill out the damaged thread.
3. Clean the drilling chips out of the hole.
IMPORTANT: Avoid a buildup of chips. Back out of the tap every few turns and remove the chips.
4. Tap the hole. Lubricate the tap with light engine oil (except aluminum).
Fig 2: Installing Thread Insert
Courtesy of GENERAL MOTORS CORP.
5. Thread the insert onto the mandrel of the installer. Engage the tang of the insert onto the end of the mandrel.
IMPORTANT: When correctly installed, the insert should be flush to one turn below the surface.
6. Lubricate the insert with light engine oil (except when installing into aluminum) and install the insert.
7. If the tang of the insert does not break off when backing out the installer, break the tang off with a drift punch.