How do you tell what has failed?
Look before you repair. A thread failure is rarely bad luck, and the repair differs by cause. A sheared internal thread, a galled thread, a cross-threaded one and an overloaded bolt each need a different answer. Apply the same thinking to the adapter.
| What you see | What it means |
|---|---|
| The adapter thread has lost its crests, the rod end is intact | The internal thread sheared: too little engagement, or a soft adapter (Q1-04) |
| Damage on the first two or three threads, the rest clean | Cross-threading, which may only need the thread chased with a correct-size tap |
| Both threads scuffed or welded-looking | Galling, a surface problem in stainless and similar pairs (K06-Q1-09) |
| A crack at the weld, rust staining or broken paint along it, or the adapter moves in the tube | A structural failure of the weld or tube end (K09-Q1-07) |
| The tube is bent, dented or cracked away from the adapter | The tube was overloaded or buckled (Q1-10) |
Check the pitch before forcing a rod end into a thread it will not take. A bolt of the wrong pitch is a common way to damage a thread in the first place.
What are the options?
Chase the thread. For minor damage or cross-threading, clean the thread with a correct-size tap. It restores the thread's form, not its strength.
Fit a thread insert. An insert restores an internal thread to its original size instead of tapping to a larger size and changing the fastener: the damaged thread is drilled out, an oversize thread is tapped, and the insert becomes the new load-bearing thread. Inserts help in softer materials and where there is vibration.
The limit is the wall. The repair adds roughly one thread size to the diameter of the hole, and a boss without enough wall has no room for it. The wall left around the thread is worked out in Q1-02: in its example, stepping the hole up one size leaves a wall of only 0.030 in. (0.76 mm), a thin skin, and an insert is not an option.
One point matters here: the insert only fixes the thread. The parent material's ability to carry the load is unchanged, so an insert in a cracked or thin part is a thread repair, not a structural repair.
Cut out the adapter and replace it. Use this when the thread is beyond repair but the tube is sound, or when the adapter is loose. It means cutting the old adapter and its weld out of the tube end, preparing the end, and fitting and joining a new one by a qualified procedure (Q1-01). The tube gets shorter. Measure the centre distance before and after, and check that the rod ends' thread adjustment still covers the length you need (K06-Q1-12).
Scrap the link. When the tube is damaged, the cracks come back, or the link is a safety part and you cannot verify the repair.
Can a cracked weld be repaired?
Not by welding over it. A cracked weld in a link that takes load is a safety question: take the link out of service and get an engineer or a qualified welder to decide (K09-Q1-07). Any repair of the weld belongs to a qualified procedure. A crack means the joint was overloaded or fatigued, so repeat the check from Q1-04 to find which link was weak. A new weld on the same design, with the same cause, will crack again.
How do you take out a seized rod end without wrecking the adapter?
Safety first, then the least destructive route.
- Support the link so it cannot fall or spring when freed.
- Do not apply heat to a bearing rod end. It can damage the race and its liner.
- Decide what you want to save. If the rod end is cheaper than the adapter, sacrifice the rod end: cut or remove it and keep the adapter's thread.
- Galling and seized threads are covered in K06-Q1-09.
What about corrosion at the joint?
Three points are specific to a tube joint.
- Inside a closed tube. A welded-in adapter closes the end, and moisture that gets in can rust the inside where you cannot see it. When you cut a joint out, look inside the tube.
- Finish after welding. A coating on a tube end is damaged by welding, so plan to finish after welding, or to repair the coating.
- Steel adapter in an aluminium tube. The two metals form a galvanic couple, and you cannot weld them to each other. In an aluminium tube use a pinned, bolted or threaded insert (Q1-01, K01-Q1-07).
What if the link is on a vehicle?
A cracked weld or loose adapter in a steering or suspension link is a safety failure, so the vehicle stays out of use until the link is replaced or a qualified person has made the repair. After the event that caused it (a rock strike, a landing, an accident) sight along the tube for a bend, and look at the other end of the link and the mount on the chassis, because the load that broke one joint went through the others. A replacement adapter has to fit the real tube (Q1-02). If the maker's data says what repair is allowed on this link, follow it. When in doubt, replace the link. The weld-in tube adapters page is the product page for the replacement part.