| 1. Identify the thread standard | Confirm whether the damaged thread is metric, Unified inch, or another standard before choosing a kit. | Metric threads are specified in millimeters; Unified threads use inch-based designations such as UNC or UNF. Do not assume that similar-looking sizes are interchangeable. |
| 2. Match the nominal diameter and pitch | Check both the thread’s nominal size and its pitch. A diameter match alone is not enough. | Common metric coarse sizes include M6 × 1.0, M8 × 1.25, and M10 × 1.5. The kit must match the original thread specification. |
| 3. Distinguish coarse and fine threads | Verify the thread series and pitch, especially when buying an inch-size kit. | For example, 1/4-20 UNC and 1/4-28 UNF have the same nominal diameter but different pitches, so a repair kit for one is not a substitute for the other. |
| 4. Check what the kit includes | Look for the correct repair tap, drill-size guidance, installation tool, and inserts or plugs required for the chosen repair method. | Many wire-insert systems use a special STI tap to form the insert’s outer thread while preserving the specified internal thread for the fastener. Follow the kit instructions rather than selecting a tap by appearance. |
| 5. Consider the parent material | Account for the material surrounding the damaged hole and the amount of material available for the repair. | Aluminum and other softer materials may benefit from a suitable threaded insert, but the repair must have enough wall thickness and clearance for the specified drill and tap sizes. |
| 6. Match insert material and service conditions | Check the insert material and any application requirements, such as corrosion exposure, temperature, or repeated assembly. | Stainless-steel inserts are commonly available, but the appropriate choice depends on the surrounding material and operating environment. Confirm material compatibility for the specific application. |
| 7. Verify depth, clearance, and repair method | Measure the usable hole depth and check whether the repair is blind or through-hole before buying. | Confirm that the insert length, drilling depth, and installation method suit the part. Use the specified drill depth and tapping procedure, and avoid damaging nearby features or breaking through a blind hole. |