can be connected to the tip and run in the air line to the tool the flow rate adjuster assembly 28 cooperates with the piston assembly 29 so as to reduce the stroke of the oil piston 64 by moving the oil piston 64 relative to the air piston 66 the adjuster screw 102 which has a splined end 102a an externally threaded intermediate section 102b and an abutment stud 102c threadably engages the threaded section 66a of the air piston as the screw 102 is advanced the end 102c engages the disc section 64a of the oil piston 64 and urges it against the biasing spring 76 thereby moving the oil piston 64 away from the threaded section 66a which effectively increases the quantity of oil delivered by increasing piston end 64c travel past supply hole 56 the adjusted assembly 28 also includes a plug like section 104 having external threads 104a at one end for cooperation with internal threads 106 in the middle section 14a the plug is axially positioned on the body 14a by means of an external shoulder 104b that abuts the end face of the body section and an o ring 108 disposed in an intermediate retaining groove 104c pneumatically seals the threaded section the outer end of the plug has inner and outer detent grooves such as 104d and 104e the plug is internally bored for cooperation with the piston 66 and splined screw 102 the piston end.