A connection is a system, not a component. The AGBA Thread System is our name for engineering all of it — bar end, upset, thread, tooling, coupler, gauges and fitting — as one thing, which is why we supply both halves.
The chain does not care which link was set badly. Any single process, done poorly, sets the strength of the whole connection.
The coupler is the easiest part of a connection to certify and the least able to make up for the rest. A Standard Mark on the sleeve says nothing about the thread cut into the bar it is joining.
Thread a bar that was never cold forged and the finest thread form in the world has been cut into a section that has already lost a fifth of its area.
A thread is not added to steel — it is carved out of it. The only question is whether the metal was put back first. IS 16172:2023 Annex G-2(b) requires the bar end to be hydraulically enlarged by cold forging before any thread is cut.
Ø32 bar · thread cut directly · M32 × 3.5
80%
of parent bar section at the thread root
One fifth of the bar machined away. The connection cannot reach 130% of yield, and it fails at the threads — brittle, inside the coupler, where nobody can see it.
Ø32 bar · end upset, then threaded · M36 × 3.5
104%
of parent bar section at the thread root
Metal is displaced outward before any cutting begins. The threaded section is stronger than the bar, so failure is forced back into the parent bar.
| Bar | Parent area | Threaded directly | % of bar | Cold forged, then threaded | % of bar |
|---|---|---|---|---|---|
| 20 mm | 314 mm² | M20 × 2.5 · 245 mm² | 77.9% | M24 × 3.0 · 353 mm² | 112.2% |
| 25 mm | 491 mm² | M25 × 3.0 · 387 mm² | 78.8% | M29 × 3.5 · 519 mm² | 105.8% |
| 32 mm | 804 mm² | M32 × 3.5 · 648 mm² | 80.5% | M36 × 3.5 · 841 mm² | 104.5% |
Stress area on ISO metric basis, As = π/4 · ((d₂+d₃)/2)². Cold forging applies to the rebar end only — AGBA couplers are machined from special alloy tube, never forged.
IS 16172:2023 places no constraint on thread form. That freedom is where the difference between one coupler and another actually lives — so we treat the thread as a designed feature, not a copied one.
| Dimension | What it is set for |
|---|---|
| Root radius | Fatigue resistance — a radiused root carries a connection through load reversal; a sharp one is where a crack starts |
| Pitch | Load distribution along the engaged threads |
| Engagement length | Strength transfer from bar to coupler |
| Outside diameter | Concrete flow and cover at the connection plane |
| Chamfer | Installation without cross-starting the thread |
A radius is only worth what the tooling actually forms. AGBA controls it as a drawing feature, gauges it, and audits sectioned couplers against it.
AGBA deploys cold forging and threading machines with trained technicians, so the bar end and the coupler come out of the same quality system.
Whether you're a contractor, consultant or distributor, our team is ready with sizing, certificates and pricing.
