A replacement nut to fit boc cylinder. Oxygen / Argoshield /Argon nut  * R/H thread only * the tubular  nut/ bolt  has a 5/8 bsp x 14 tpi thread  and measures 1" across the hexagon flats

                      

 The spindle has a 27 U.N.F  fine special brass treads  on 1/2" stock this type is fitted with a rubber  sealing  ogee ring  which is replaceable

        when required