Repair of Threaded Holes

GENERAL INFORMATION

Repair of Threaded Holes

Warning.

To avoid eye injury, wear safety goggles.

Damaged threaded holes can be repaired by drilling out, tapping to a larger diameter, and installing threaded inserts.

PROCEDURE.

1. Measure the diameter, pitch, and depth of the thread in the damaged hole. If

necessary, use depth stop collars fitted to the cutting tool (drill, tap). The height of the collars is determined by the depth of the

hole to be machined.

Warning.

Determine the required drill diameter and tap size according to the instructions

supplied with the repair kit by the manufacturer.

2. Drill out the hole with damaged thread. Remove chips and burrs.

3. Tap the thread. Lubricate the tap with engine oil beforehand (except when tapping an aluminum cylinder block). Clean the thread.

Warning.

To avoid chips clogging the hole, periodically (after every

few working turns) back out and clean the tap.

4. Screw the threaded insert onto the installation tool mandrel, see figure. Repair of Threaded Holes. Engage the insert tip with the mandrel.

5. Lubricate the outer thread of the insert with engine oil (except when installing the insert into an aluminum block) and screw it into the hole.

Warning.

When installed correctly, the insert must be recessed one turn

below the mating surface.

6. If the insert tip did not break off when the mandrel was unscrewed, remove it with a screw extractor.