... 20 years experience 1,Name: Steel hex coupling;steel coupling;hex coupling2,For the similar coupling ,what can we do ?(1), Ability ... for the material of this kind of coupling : Grade3.6,4.6,4.8,5.6,6.8 ... 9.8,10.9,12.9,etcCarbon steelGr.B,Gr.C,Gr.D,Gr.36,Gr.58,1010,1015,1016,1020,1045,etcAlloy steel4130 ... hardware fastener ,especially the cutting/turning parts. Steel hex coupling