• Medium cutting speed between the low and high selected cutting speeds. Feed rates for other cast metals may be selected
from machining handbooks. A depth of cut up to 0.1 in. (2.54 cm) may be used for other cast metals if the disc does not slip in the chuck. Deeper cuts increase the amount of flank wear, which provides more area for measurements.
remove scale and solidification effects on the sub- surface microstructure. One of the selected cutting speeds is programmed for the first test campaign or test insert run and the cutting tool/workpiece inter- face is flooded with the water soluble cutting fluid. An up-sharp nose or corner of the cutting tool insert is used for each campaign. The cutting tool path is programmed to take a cut or pass length leaving 0.5-in. diameter of uncut metal at the disc’s center (Fig. 2). The tip of the cutting tool is programmed to disengage quickly without impacting the uncut metal at the disc’s center. The test campaign is stopped frequently, usually after a completed pass, to remove and measure the flank wear on the cutting tool insert at a 30x magnification. The width of the wear land is measured in a zone of the cutting edge plane perpen- dicular to the major cutting edge, according to the measuring procedure in the International Standards Organization Specification 3685-1977 (E). The time to complete one facing pass is measured
2
and recorded. The flank wear is recorded, along with the number of completed passes on the test sheet. After measuring the insert, it is replaced, properly seated and reclamped in the tool holder, which has been cleared of chips and cutting fluid buildup. Unusual wear is noted and/or macrophotographed for further explanation. The cutting tool life is calculated by multiplying the number of passes by the time to complete a pass. The time taken to reach the flank wear end of life criterion, cutting tool life, is recorded in minutes on the test report sheet. Te procedure is repeated with the other selected
speeds. Finn recommends a minimum of five test cam- paigns that include: • Two test runs at the low cutting speed • One test run at the medium cutting speed • Two test runs at the high cutting speed. More test campaigns with the repetitions or other cutting speeds within the selected range will improve the test’s accuracy.
March 2013 MODERN CASTING | 61
Procedure After clamping the hub in a three or
four-jaw chuck of a turning center, the operator removes 0.02 in. (0.51 mm) off the face of the disc in a truing or skin pass to
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