... than 20 years experience 1,Name: Adjustable screw for sewing machine;adjustable screw;screw for sewing machine 2,For the similar screw,what can we do ?(1 ... ), Ability for the material of this kind of screw: Grade3.6,4.6,4 ... .8,5.6,6.8,8.8,9.8,10.9,12.9,etcCarbon steelGr.B,Gr.C ...