3
Results and Conclusions
A graph of the
results is plotted with cutting tool life on the
y axis in minutes, and the cutting speed is plotted on the x axis in surface feet per minute (sfpm). The logarithmic line of best-fit is plot- ted through the data points (Fig. 3). Error or confidence bars may be added to the graph and used to compare cast discs from other heat lots or grades. The Taylor Line is the loga-
rithmic regressions line from a plot of several observed cutting tool lives over a range of cutting speeds. Several characteristics of the Taylor Line may be used to compare different heat lots and cast iron grades. The intercept of the Taylor Line at a time on the y axis is popular in this type of machinability testing. For example, the intercept of 30 minutes at the x axis could be used as the speed that predicts a 30-minute life on the Taylor Line. Investigators de- cided to call this attribute the V30 machinability value of the casting. Several other parameters of the Taylor Line are used to compare
machinability, such as: • Compare the overlay of the observed cutting tool lives and Taylor Lines on the same graph
• Compare the slope of the Taylor Lines
• Compare the regression line formula of the Taylor Lines. The machinability test mythol-
ogy was certified in metalcasting machine shops, such as Dura- Bar and Waupaca Foundry, and machining laboratories including Kennametal and TechSolve.
@
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Mar/Apr 2013 | METAL CASTING DESIGN & PURCHASING | 37
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