... 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 ... lots of risks.P.S:For us,the most competitive industry is machined hardware fastener ,especially the cutting/turning parts. Steel ...