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

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[6] Buffing Wheel <strong>Experiments</strong>Buffing WheelsBuffing wheels are commonly used to finish the knifesharpening process. Therefore, a study was done in which the stainless steel blades werefinished by buffing on standard felt and cloth wheels. The buffing operation was carriedout by Master Bladesmith, Alfred Pendray of Williston FL. The T edge of the stainlessblades were resharpened to a 2β edge angle of 40 o using progressively the 220, 400 and600 grit wheels of the Tru Hone machine. In addition blades were produced with the Aedge geometry of Fig. 5 using the same procedure. A jig was made to firmly hold theblades into the buffing wheel and the 4 buffing procedures shown in Table 3 were carriedout on both the T and A edges. The 555 polishing compound is a product of Brownells,Inc. The compound is embedded in a wax-like bar similar to the green chrome oxidecompound used above with the leather strops and wheels. The abrasive is aluminumoxide, and the White has an average particle size of under 1 micron, while the black is inthe 1-5 micron size range [5].To the eye, all samples showed a shinnyeffect from the buffing procedure, butthe effect was distinctly morepronounced on the blade of procedure 4.4 (2 steps)The blades were examined by twotechniques. First, the center 1 inchsection of the blades was cut out with awater cooled cut-off wheel and the edge along this section was examined in the SEM.Second, a 1/8 inch length was cut off the remaining blade pieces at each side of the centersection. These 2 pieces from each blade were mounted in plastic and polished throughone micron diamond using standard metallographic polishing techniques. Aftermounting the samples were ground heavily on coarse (50 grit) paper to remove any bursthat were generated when the cut-off blade sectioned the tip region of the blade. Thepolished sections were examined in the optical microscope toreveal the cross sectional shape of the sections.SEM Study of the Buffed Edges The SEM photosin this study were taken on the blades only in Edge view. Anedge view of an unbuffed blade of the as-ground condition isshown in Fig. 39. Comparison of the buffed blade micrographsto it will allow an evaluation of the effect of the buffingoperation. All of the 8 buffed blade edges of Table 3 (4 bladeseach with A & T edges) were examined in the SEM and Fig. 40presents representative micrographs of three of the blades. Thedesignation of T or A on the micrographs refers to the bladeedge examined. For example, 2T means the T edge of blade 2of Table 3 and 3A means the A edge of blade 3 of Table 3.After buffing the blade edges appeared smooth and shinny to theeye, and Fig. 40 shows that the abrasive grooves produced byTable 3 The 4 buffing proceduresBlade No. Wheel Compound No. passes Pressure1 Medium felt 555 White 4 Moderate2 Medium felt 555 White 2 Medium3 Stitched cloth 555 White 2 MediumCloth 555 Black 2 MediumFelt 555 White 2 Med.32
the 600 grit wheels were largely removed by the buffing operation.A small bur was consistently found on all of the blades and a measure of the edgewidth was made on each of the blades using the SEM micorgraphs. Table 4 presents asummary of the range of edge width values found for the 8 blades. There were two clearresults of this study. (1) The T edge of the blades possessed thinner burs than the Aedges. In addition, the burs along the T edge were more uniform than along the A edge.This result can be seen by comparing Blade 2T to Blade 3Ain Fig. 40. (2) The use of the 2-step buffing operation onblades 4, consistently produced thinner burs than any of thesingle step operations used on blades 1 to 3. The variationsof the buffing procedures employed with blades 1 to 3, seeTable 3, did not produce any significant change in edgequality.Table 4 Measurements of edge widths.Blade Edge width Blade Edge width1T 0.8-2 µm 1A 1-5 µm2T 0.8-2 µm 2A 1-5 µm3T 0.8-2 µm 3A 1-5 µm4T 0.3 -2µm 4A 0.5 - 5 µmThe 2-step buffing operation used the coarser compound for the first step on acloth wheel, followed by the finer compound on a felt wheel. It is common practice inmetallograhic polishing of metals to proceed from coarse to fine grit abrasives. It hasbeen the experience of this author that employing this progressive type of polishing ismuch more effective at producing smoother final surfaces. It seems likely that a similareffect occurs here, with the use of a 2-step progressive grit size procedure able to reducethe edge bur more effectively than the use of just the final fine grit compound.Additional experiments would be needed to verify this possibility. The reason why thebur size on the A edges were significantly larger than on the T edges is unknown. Herealso, additional experiments are needed to determine the source of this variation.Cross Sectional OutlinesThe optical images of the polished cross sections ofthe blades were collected digitally. The digital images were then processed on a pc tosuperimpose a white line along the outer surfaces of the blades, as shown for two of theblades in Fig. 41. The extension of the outlines to the crossover point allows a reasonableestimate of the original shape of the blade prior to buffing. The original geometry of theedge was known from sections of unbuffed blades. It is apparent from Fig. 41 that one33
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: 3 Dropping the 2β edge angle from
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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