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

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can estimate from these micrographs how far back the as-ground edge has been polishedaway by the buffing operation.The distance of retraction of the tip from the extrapolated lines was measured foreach pair of blade sections and the results are presented in the left 3 columns of Table 5for the A edges. The average retraction distance is 73 and 42 microns for blades 1A and4A, and 25 and 39 microns for blades 2A and 3A, respectively. One would expect moreretraction from blades 1 and 4 because these blades had 4 passes rather than the 2 of theother blades, and the data is consistent with this expectation. The corresponding resultsfor the T sections are not as easy to interpret. The outline of the original blade shape wasfitted to that of the buffed blades by moving the outline onto the buffed blade image sothe lines from the bottom and top faces fit the buffed blade image. If the buffingremoved significant material from the top and bottom faces appearing on themicrographs, then the outline would move further to the right than they should have.This would have the effect of reducing the contraction distance from the true tip position.The average retraction distance forblades 1T and 4T is (38+54)/2 = 46 Table 5 Measurement of retraction distances.µm, compared to (51+54)/2 = 52.5 µmfor blades 2T and 3T, which is notconsistent with the larger number ofpasses for blades 1 and 4. Perhaps thisinconsistency results from the fittingproblem. Nevertheless, the data doshow that the T edges have retractedby a minimum of around 40 to 55microns during the buffing.S1ABS1ADS2ABS2ADS3ABS3ADS4ABS4AD75 µm7224274236384673 µm253942S1TBS1TDS2TBS2TDS3TBS3TDS4TBS4TD33 µm43633944686148Blade Retraction Avg. Retr. Blade Retraction Avg. Retr.The data of this study show clearly that any bur on the tip from the originalgrinding operation must have been removed by the buffing operation. For example, thedata of Table 5 show that the original tip has receded by at least 25 µm on the mostlightly buffed A edge and probably by at least 40 to 50 µm on the most lightly buffed Tblade. The bur size on the final blades are in the 1 to 5 µm range, and on the original asgroundblades they were probably no larger than 7 µm at the most. Looking at Fig. 41 it is38µm51565434
seen that the buffing action is removing a very significantamount of metal from the tip region, very much larger thanthe size of the burs involved either on the final or the originalas-ground blades. So it is apparent that any bur on the buffed blades was produced by thebuffing action itself. At the conclusion of this phase of the buffing study it was surmisedthat perhaps bur formation in the buffing operation might be reduced if the buffing wasdone with a lighter pressure and this lead to the following study.Buffing study on a non stainless steel To investigate the effects of using a ligherbuffing pressure, and expand the buffing study to non stainless steel blades, Al Pendrayprepared a set of 3 blades made from austempered 52100 steel. The hardness of theaustempered blades was HRC = 56. Figure 42 illustrates the blade shape. The endmarked CL was held in a clamp and the opposite end of the blades was sharpened on abelt grinder using 3M Trizact belts A-65, A-30, A-16 and A-6, which correspond to gritsof 280, 700, 1200 and 2000,Table 5 Sharpening procedure of the 4 blades.respectively. The blades contacted thebelt just after it left the pulley No. Belt Series Buffingproducing a "slack belt" grindingeffect. After the belt grindingoperation the blades were lightlybuffed and/or stropped on leather asdescribed in Table 5.AP-1 280-700-1200-2000 White 555 on cloth wheelAP-2 280-700-1200-2000 White 555 on cloth wheel+ plain leather strop.AP-3 280-700 White 555 on felt wheelFigure 43 presents the SEM micrographs of blade AP-1. The two faces of theblade are fairly smooth indicating that the combination of the 2000 grit belt and thebuffing have been effective in giving a well polished surface. However, there is adominant bur along the edge and the Edge View 3000x micrograph indicates the edge-onbur width to be around 1 to 1.2 µm wide. The bur has been curled around the down faceshown on the right of Fig. 43.CLSize: 3.3" x 0.91" x 0.098"Sharpened surfaceFigure 42 Geometry of 52100 blades.35
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 11 and 12: Even on freshly dressed wheels a 2
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: the 600 grit wheels were largely re
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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