Method and apparatus for machining

A method of machining a workpiece with an insert having a top surface terminating with a cutting edge, said insert being mounted within a holder formed with at least one discharge orifice oriented to direct coolant onto the top surface of said insert toward said cutting edge, comprising the steps of:

• positioning the discharge orifice relative to the insert mounted in the holder so that the distance between the cutting edge of the insert and the discharge orifice is in the range of about 0.040 inch to 0.440 inch;
• engaging the workpiece with the cutting edge of the insert to form chips having a bottom surface overlying the top surface of the cutting insert;
• rotating the holder or the workpiece;
• ejecting a jet of coolant from the discharge orifice onto the top surface of the insert and beneath the bottom surface of the chip substantially perpendicularly to the cutting edge of the insert at a velocity of at least 250 feet per second;
• moving the insert with respect to the workpiece at a feed rate in the range of about 0.004 to 0.025 inches per revolution of the holder or workpiece.

Apparatus for machining a workpiece with a cutting insert having a top surface terminating with a cutting edge, comprising:

• a support bar formed with a cavity having a bottom wall, rear wall, top wall and side wall, said bottom wall being formed with a seat adapted to mount an insert with the top surface being exposed and the cutting edge projecting from said support bar;
• an orifice block mounted on said bottom wall of said cavity in said support bar atop the cutting insert;
• said orifice block being formed with an internal passageway, said internal passageway decreasing in cross section from an enlarged entrance opening to a discharge orifice lying on the top surface of the insert and being spaced from the cutting edge;
• adjustment means mounted to said support bar for laterally adjusting the position of said orifice block along said bottom wall of said cavity atop the insert so as to vary the space between said discharge orifice and the cutting edge of the insert;
• and
• coolant delivery means for conveying coolant under high pressure and low velocity to said entrance opening, said coolant being accelerated within said internal passageway and ejected at high velocity from said discharge opening across the top surface of the cutting insert.

A method of breaking chips produced by the relative rotary engagement between the cutting edge at the top surface of the insert and a workpiece, said insert being mounted within a holder formed with at least one discharge orifice oriented to direct coolant onto the top surface of the insert toward the cutting edge, comprising:

• positioning the discharge orifice relative to the insert mounted in the holder so that the distance between the cutting edge of the insert and the discharge orifice of the holder is in the range of about 0.040 inch to 0.440 inch;
• moving the insert whth respect to the workpiece at a feed rate in the range of about 0.004 to 0.025 inches per revolution of the holder or workpiece;
• ejecting a jet of coolant from the discharge orifice onto the top surface of the insert and beneath a bottom surface of the chip overlying the top surface of the insert at a velocity of about 250 feet per second;
• increasing the velocity of the coolant jet from 250 feet per second until the chips are broken from the workpiece in small lengths up to a velocity of about 1,000 feet per second.