Support BladeForums! Paid memberships don't see ads! For the Work Sharp Ken Onion Blade Grinding Attachment (BGA), previous threads have examined offsets between the angle setting of the tool and the resulting apex angle. To gain more understanding, I conducted an experiment using bar stock of varying thicknesses, on which varying BGA settings were used. I supplemented these data with additional data using knife blades of varying thicknesses. Conclusion: The thickness of the blade stock immediately behind the edge apex determines the magnitude of the offset between the BGA setting and the resulting apex angle. Experimental results: The results of this experiment are shown in this chart: This chart shows data in 5 series, where each series represents a different thickness of blade stock. Each series has been plotted using circular markers to show actual data points. Series including 3 or more data points show a trendline created by linear regression of the data. Numerical values of the regression lines are shown in the legend in the lower right area of the chart. The 3 thickest series (0.125", 0.094" and 0.062") show data obtained by sharpening blank blade stock. Each of these series includes 6 data points. The 2 thinnest series show data obtained by sharpening real knives. The series for blade thickness 0.012" includes 3 data points obtained by sharpening Opinel folding knives. The series for blade thickness 0.008" includes 1 data point obtained by sharpening a Shun kitchen knife. The dotted green line shows the theoretical ideal case, where any BGA setting results in an apex angle exactly twice that setting. Discussion and Interpretation: All series having multiple data points shows extremely good linear fit to the data. This indicates the total experimental system (human, machine, materials and measurement) is well-controlled and precise. The data point from the thinnest blade stock falls on the theoretical ideal line; there is no offset between the BGA setting and the resulting apex angle. I expect this scenario to be representative of many common use cases for the typical user, where the presence of a primary bevel on the blade reduces the effective blade stock thickness to a regime where the offset is insignificant. Every series from thicker blade stock thicknesses shows offset between the BGA setting and the resulting apex angle. As the blade stock thickness increases, the magnitude of the offset increases. Consequently, sharpening thick blades will result in large offsets. Thicker blades cannot be sharpened to angles as acute as are possible for thinner blades.