Pumps included in this class; air and gas compressors; compressed air motors; hoists; motor activated tools for drilling, thread cutting, screw driving, nut tightening, grinding, sawing, chipping and binding electric cable assemblies; pneumatic hammers; portable rotary earth drilling machines; components for rotary earth drilling machines, namely, drawworks (hoists), rotary table type drill stem driving units, pulley blocks (travelling and crown), and drill pipe; rock drilling machines; pressure fluid activated percussion rock drills, rock drill supports and advance causing mechanisms, rock drill stem components, namely, drill rods, drill rod couplings and drill bits all being goods included in this class