... -40mm Thread Pitch:2.5mm,3.0mm,3.5mm rebar coupler with threading rolling end Materials: 45# carbon steel. Specifications: D14mm- ... Upset forging machine to enlarge the end of rebar.Secong, use GZL-45 Threading machine to process screw on the enlarged end ... .Third, use one rebar coupler to connect two rebar ends. rebar coupler with threading ...