Knife sharpening revisited

Robert Dewey

Some 10 years ago, I put together an article on the subject of knife sharpening. It was at a time when there was a lot of discussion as to what was the preferred cutting edge geometry. Diamond sharpeners were beginning to dominate the scene. Opinions were becoming replaced with facts and a lot of the mystique about knife sharpening was being resolved.

This article looks at my current technique, aimed essentially at Australian hunters and fishermen and the food preparation group. To use as an example, I will relate a recent experience where a colleague asked me to sharpen his blunt model 621 Dewey-made sheepsfoot paring knife.

This design was highlighted in Edition 66 of the Australian Hunter magazine. The knife is made from 1.4116 stainless steel, hardened and tempered to HRC 54-56. The blade thickness is 1.5mm and is fashioned with flat ground bevels that meet at a cutting edge of zero thickness and finished with a barely discernible cutting edge vee.

The knife concerned had been resharpened a number of times using a pull through sharpener and, by eye, it could be seen that shoulders had formed, roughly ½mm in thickness – that is, his knife was seriously blunt. I explained that we would need to reset the bevels so that, once again, they met at a point of zero thickness.

Using a 25cm flat file with an industrial 600 grit diamond surface, I filed the bevels accordingly. With such a thin blade, this filing took about five minutes. I could have used a quality standard second cut file, but the diamond gave me less work to clean up the file scratch marks.

I then used a hand-held 600 grit Eze-Lap diamond hone to form a cutting edge vee. To prepare this vee, I laid the hone flat on the bevel then raised the back of the hone approximately 3mm. I honed the edge, giving an equal number of strokes on both sides of the blade. This was continued until a feather was raised before I used the hone to buff it away. This operation took just a few minutes.

I demonstrated its sharpness using the thumbnail test ‑ that is when pulled against the thumbnail, it bites. You have reached your maximum level of sharpness.

This process is needed in its entirety only when you have resharpened/touched up your blade many times and have developed a shoulder. At that point, a further touch up will not produce a sharp edge. This procedure is applicable for all filleting, skinning and cooking knives.

For the hunter, the knife used as the indestructible unit of the three-knife kit should have bevels to meet at a point of approximately ¼mm thickness. This thickness is dependent upon the quality of the blade steel. For example, with a poor-quality steel blade to hold its edge, a thicker end point may be needed.

The quality of the blade will largely determine how long before a touch up or resharpening is needed. It can be as short as after several cuts or up to six months frequent use. For example, my 621 parer, used almost every day, holds its edge for several months before half a dozen strokes with the 600 grit diamond hone are needed. After approximately 20 years of use, we have not yet produced a recognisable shoulder.

Once I had sharpened my colleague’s entire kit of knives, my advice was that, apart from serrated blades, a 600 grit diamond hone was the only sharpening tool needed until a shoulder does come along. Then use can be made of a diamond or conventional file, a diamond stone or powered equipment. To remove the shoulder and re-establish flat bevels is a tedious job and the subject has been written about in previous editions of Australian Hunter.

I made the point to my colleague that he should use the diamond hone sparingly as they are aggressive. However, it was evident that the difference in my blade size, compared with a new blade, was barely discernible notwithstanding 20 years of service.

From this example, we can deduce a number of things:

● To put the final cutting edge vee on a knife is a simple technical exercise.

● The procedure outlined can be used on all of your knives also including items such as garden tools.

● The procedure can be taught to your partner and children. The pleasure of using a knife that both holds its edge and produces effortless cuts makes it worthwhile.

● If your choice is to use a 25cm diamond coated rod in lieu of a hand-held hone, the process is unchanged.

● The price of a 600 grit diamond hand-held hone is about $25 and, for the casual hunter and domestic chef, this item will be effective for approximately five years. If using a 25cm diamond rod, it will be operative for more or less 20 years.

● Leaving aside the period to remove a shoulder and reshape the bevels, the usual time to touch up the vee is about five minutes.

● The difficulty with shoulders has not changed. A user will raise a shoulder after repeated re-sharpenings irrespective of using hand-held equipment or a pull through type machine. If not removed, your knife will be blunt.

● The quality of your edge sharpness is almost totally dependent upon bringing your bevels near to or zero at the point of meeting and prior to honing the cutting edge vee. However, how long this sharpness lasts depends upon the quality of your blade steel and its heat treatment.

At all times, keep it simple, recognise and follow the few key points. You will then enjoy the use of your knives and their upkeep.

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