Key-Locking Insert
Threaded Inserts · Keensert (brand) · solid bushing insert · key insert
Definition: A key-locking insert (Keensert is the leading brand) is a solid threaded bushing with locking keys driven into the parent material, for high-strength thread repair in soft metals.
Anatomy
■ Head■ Shank■ Threads■ Point
Governing standards: ASME B18.29.2
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| 1/4-20 | M6 | 0.276 drill | 0.295 c-bore |
| 5/16-18 | M8 | 0.354 drill | 0.375 c-bore |
| 3/8-16 | M10 | 0.433 drill | 0.453 c-bore |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Carbon steel | carbon steel | — | Standard |
| Stainless | 304 stainless | — | Corrosion-resistant |
Materials
- Carbon steel
- Stainless steel 304
Pros & Cons
Pros
- Extremely strong — solid bushing, not a coil
- Locks in place with keys (cannot unwind)
- Excellent in soft parent metals
Cons
- Needs a larger hole and counterbore
- More expensive than a helical insert
- Thick boss required around the hole
Typical Uses
- Heavy-duty thread repair in aluminum and cast iron
- Aerospace and defense
- High-cycle threaded holes
- Repairing damaged machine housings
Alternatives & Related
- Helical Insert — Compact, standard repair where space is tight
- Rivet Nut — Thin-sheet applications
Where to Buy
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FAQ
Keensert vs helicoil — which is stronger?
A key-locking insert is stronger in soft parent materials because it is a solid bushing with a larger external area and positive key locking. A helical insert wins where space and boss size are limited.
How do you install a key-locking insert?
Drill and counterbore to spec, tap the outer thread, thread the insert in, and drive the locking keys down until they seat. It is permanent without drilling out.