Rotary downhole cutting tool

In a downhole cutting tool of the type that is suspended by fluid conducting continuous tubing and responsive to increased fluid pressure to effect a tubular goods cutting operation, the apparatus comprising:

• an elongate body of revolution having a sidewall, upper end and lower end with the upper end connected to said tubing, said body having an axial cylinder cavity disposed adjacent the lower end and a reduced bore axially communicating downhole;
• plural, equi-spaced longitudinal slots formed radially to extend outward from the cylinder cavity through the body sidewall;
• plural, generally flat cutter bars pivotally suspended in each of said plural longitudinal slots, each cutter bar having a pivot hole at the upper end and extending downward to form a linear camming surface at the lower, radially inward edge, while the radially outward edge is formed as a cutter blade extending into a hook and point portion;
• a piston member disposed slidably in the lower portion of the body axial cylinder cavity, said piston member having an upper camming shoulder extending upward axially to form a piston rod and foot end;
• a compression spring disposed in said axial cylinder cavity and seated against said piston member end to maintain downward spring pressure;
• plural porting means in said body of revolution directing fluid under pressure from the body upper end down to the body lower end for communication with said axial cylinder cavity below the piston member;
• whereby sufficiently increased fluid pressure forces the piston member upward while urging the piston member upper camming shoulder against the plural cutter bar linear camming surfaces thereby to force the cutter bars outward into cutting contact with surrounding tubular goods.