Experiments on Knife Sharpening John D. Verhoeven ... - BushcraftUK

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machine, both with a 220 grit coarseness, did not reveal any significant differences inSEM images similar to those presented in Fig. 10.The Tru Hone directions recommend that the last step of the knife sharpeningprocess should be accomplished by turning the knob that controls the wheel spacingthrough a specific sequence of colored marks on the knob. It was determined that thesedirections correspond to an increase of the final 2β edge angle by increments of around3.5 degrees on each of the last 2 sets of passes. An experiment was carried out using the1000 grit wheels to examine the effect of incrementing the 2β edge grinding angle on thefinal pass. A control set of blades was first ground on 600 grit wheel at a 2β edge angleof 38.8 degrees. They were then ground with the 1000 grit wheels at a 2β edge angle of41.3 degrees with the final step consisting of 3 back-and-forth passes under holder armpressure (a very light pressure) at the slowest wheel speed, S = 1. The pull rate throughthe wheels was estimated to be around 2 to 3 inches per second. An edge view of acontrol blade is shown at the left of Fig. 13. The center blade of Fig. 13 was a controlblade that had been given one additional back-and-forth pass under holder arm pressureat the slowest speed with the 2β edge angle increased by 2.2 degrees. The right blade ofFig. 13 had the single additional pass done with the angle increased by 7.2 degrees.Examination of the micrographs of Fig. 13 demonstrate a couple of interestingthings. First, one can clearly see the regions along the edge that was ground by the finalback and forth pass. This result shows that a single back and forth pass under the lightgrinding conditions removes a significant portion of the blade surface. Second, the edgebur produced by the small increase of the final 2β edge grind angle does not appear to bereduced in size. So, there does not appear to be a significant advantage of using a smallincrease in edge angle for the final grind.A series of experiments was done on the Tru Hone machine with the 2β edgeangle reduced to 30 and 20 degrees. As the angle decreases the overlap of theinterpenetrating wheels becomes less and any slight non uniformity in wheel radiuscauses the knife edge to undulate up and down as it passes through the wheel sets. Thevertical undulations in turn produce variation in the grind angle and the edge straightness.10
Even on freshly dressed wheels a 2β edge angle of 20 degrees was too small to givereasonable edge quality. At 30 degrees the results were only nominally acceptable, butabove around 35 degrees consistently good results were obtained.Conclusions1 The 1000 grit wheels produce a very smooth surface with a small burr along the edge.The burr width as viewed edge-on in the SEM is consistently in the 1 to 1.5 micronrange. The burr formation appears to be an inherent feature of the sharpening action ofthe Tru Hone machine. It cannot be reduced in size by employing very small addedgrindings at slightly larger 2β angles. Low speeds appeared best for uniform grinding,but varying the final wheel speeds between 1 and 2 did not have a statistically observableeffect on the burr width.2 The 600 and 200 grit wheels produced surfaces that were difficult to tell apart. In bothcases the face abrasion marks were significantly larger and the edge burrs significantlywider and more convoluted than found with the 1000 grit wheels. In addition, the faceview of the edges were significantly rougher and less straight than on the 1000 gritwheels. Nevertheless, the edges produced by the 600 and 200 girt wheels are quite thin,with a burr width on the order of 2 to 3 µm on the 600 wheels and 2 to 4 µm on the 200wheels. And, from a practical point of view, the edges are quite sharp, being able to cutarm hair as well as the 1000 grit edges. Neither cut hair as easily, however, as a razorblade. This later fact is probably due in large part to the much smaller edge angle of therazor blades, 2β of 17 o versus 40 o .3 Optimum edge formation requires the wheels to be concentric with the rotating shaft sothat there is no motion of the wheel surface along the radius upon rotation. Such motionproduces edges that undulate along the edge length. The undulation effect is mostpronounced when using the wheels with the smallest overlap, which is required for thesmallest 2β angles. The undulations observed in these experiments were minor at 2βvalues of 35 to 45 degrees. However, at 2β edge angles of around 30 o and less theundulations became too severe to allow satisfactory sharpening.11
Page 1 and 2: Experiments on Kni
Page 4 and 5: as a guide to good sharpening techn
Page 6 and 7: machine ground. The final 2β edge
Page 8: [2] Experiments wi
Page 13 and 14: ledges of material has broken out o
Page 15 and 16: at the 2β edge angles of 50 and 70
Page 17 and 18: 7 All of the blades that were studi
Page 19 and 20: Japanese waterstones plus leather s
Page 21 and 22: Figs. 23-24. The blade of Fig. 25 w
Page 23 and 24: Figs 23 to 26. It appears that the
Page 25 and 26: [5] Experiments wi
Page 27 and 28: the 2β target hone angle set to ar
Page 29 and 30: lade of Fig. 33 along part of the l
Page 31 and 32: 3 Dropping the 2β edge angle from
Page 33 and 34: the 600 grit wheels were largely re
Page 35 and 36: seen that the buffing action is rem
Page 37 and 38: [7] Experiments on
Page 39 and 40: found that the softer steel produce
Page 41 and 42: optimum EW values found for afinal
Page 43 and 44: [9] Summary and ConclusionsThese ex
Page 45 and 46: 6 When the 2β edge angle is reduce
Page 47 and 48: Appendix 1Edge angle measurements w
Page 49 and 50: β = arc cosine((R 2 +L 2 -Y 2 -h 2
Page 51 and 52: YY = 45.5 mmLThese parameters can b
Page 53 and 54: Appendix 3The Tru Hone Sharpening M
Page 55: To overcome this problem withgrindi

Experiments on Knife Sharpening John D. Verhoeven ... - BushcraftUK

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