Another one to play with....
NT
Sharpen cutlery
Sharp kitchen knives make hard jobs easy, reduce fatigue, and reduce the risk of accident due to putting too much force on a knife and losing control.
==Considerations== ===Metals=== The quality of steel used in knives varies fairly widely. Some knives can take a very sharp edge, most can be made fairly sharp, and the occasional bad one is barely capable of becoming sharp at all.
===Angles=== Specific angles are best for specific metals and jobs, but with kitchen knives one is usually working with unknown budget metal, and not looking for a razor edge. The thinner the angle, the more sharp the blade is initially, but the quicker it blunts. And with popular low cost cutlery, blunting at narrow angles can be very quick. Also the poorest quality metal, found on some table knives, is sometimes unable to take 35 degrees without the cutting edge pitting during grinding.
The following angles work well for me:
Cutting knives: 30 degrees.
- sharp
- blunts quickly if used with glass boards or ceramic plates
Table knives: 40 degrees
- mildly sharp
- child friendly
- works on any steel
- retains its mildly sharp edge well
- Not very sharp, but a big improvement on a blunt knife.
Its possible to place a printed angle under the grinder to act as a guide if wanted. Personally I don't lose sleep over precision here, kitchen knives are far from critical high performance tools. If you buy high cost knives, you should follow the original grinding angles to ensure you get the best possible performance. Most people however are working with unknown material, and its not possible to specify what angle will give the best performance for each knife.
If you're determined to tweak your grinding angles to get peak performance out of each knife, it may be worth nothing that in my experience the worst quality metal is found not on cheapo knives, but on pretty table knives from a popular major manufacturer, one most buyers would regard as quality.
==Serrated blades== Serration is a way to get much of the effect of sharpness without real sharpness being present. Serration is widely disliked among knife sharpeners, but its an easy way to get cutting ability from cheap metal, its liked by many end users, and it has its uses, such as cutting frozen food. Consequently it may be wished to sharpen serrated knives without loss of serration.
There's no easy way to maintain the serrated shape indefinitely while sharpening using home equipment. There are however a few successful ways to sharpen serrated knives.
===Sharpen the back=== Often knives are serrated asymmetrically, with serrations ground on one side only. In this case the flat other side of the blade can be ground. Only a small amount of grinding is needed. A final single very light pass on the serrated side removes any burr.
===Sharpen the tips=== Where the above method doesn't produce enough sharpening, the knife may be ground on the serrated side(s) too. The idea here is not to thoroughly grind all areas of the blade, but rather to make the usual fairly quick pass over the blade. This will sharpen the tips only, giving a big improvement in performance. Its good enough for most uses.
===Rough edge=== This technique produces a rough edge with mini serrations, and works well with an angle grinder. I don't know if its possible to do this approach with other grinding tools. The blade is sharpened as normal, but its moved over the grinder disc as quickly as can be done safely, rather than gradually. The idea is to pass the whole length of the blade over the disc in about half a second. The result is fairly sharp, but rough and uneven. It effectively creates ungraceful serrations. A rough old grinding disc creates more serration than a new smooth one.
This method isn't often the best choice, but can be used where existing serrations are too uneven to sharpen usefully, and where conversion to a plain edge is unworkable for some reason, eg not enough metal left, or would require grinding an excessive amount of metal away. Its also a very quick way to deal with serrated knifes that are barely worth the trouble of sharpening.
===Sharpen all=== In principle its possible to sharpen cresent shaped serrations and maintain their shape. However its very time consuming and not very pointful, so not normally done.
===Plain blade conversion=== The final option is to remove enough metal to convert the knife to a plain blade. This is usually not necessary, but is the only way to ensure a blade that's sharp every millimetre of its length.
==One sided blades== Many knives come ground on one side only. This causes them to wander off line when cutting, which is a pain in the kitchen. Its a good idea to grind them on the unground side to reduce this tendency, only making a final burr removing pass on the originally ground side.
==Sharpening tools== There are a few ways to sharpen kitchen blades.
===Kitchen knife sharpener=== Many low cost motorised domestic knife sharpeners are available. One go with one of these caused me to abandon all hope.
===Bench grinder=== Bench grinders are the best option in most respects. They are the standard engineer's choice for sharpening a wide range of blades. They don't look particularly graceful in the kitchen though. They also lack the speed of an angle grinder.
===Block=== Manual sharpening is slow, and stock removal even slower. Nevertheless some people prefer this approach.
===Steel=== A traditional steel doesn't grind. Rather it restores a microscopically bent cutting edge by restraightening it. These were used between sharpenings as an intermediate way to prolong sharpness.
Modern performance knives don't use steel that suffers this fate, so a steel isn't much use with them. However cheaper knives do use softer metal, and may benefit from use of a steel.
===Abrasive Steel=== The abrasive steel is a traditional steel but with some added abrasive. It primarily acts like a traditional steel, but also provides a little grinding as well, thus prolonging sharpening intervals further. However hand powered grinding of any sort is a labour intensive way to sharpen knives compared to machine grinding.
===Sandpaper=== Sandpaper may be used on a dead flat surface (eg glass) for sharpening. This has popularly become known as the 'scary sharp' method, as by progressing through increasingly fine grades its possible to achieve a very high level of sharpness.
===Angle grinder=== The suggestion of using an [[angle grinder]] to sharpen knives often raises eyebrows. However they are very fast and effective, able to sharpen a totally blunt knife in 20-30 seconds, and remove stock to create a new edge in under a minute. This speed makes it easy and practical to sharpen all one's knives quickly, table knives included. For busy people this is a real advantage.
====Flaws==== As sharpeners, angle grinders have some sizeable flaws, and some precautions are very necessary.
The knife blade must be kept moving, don't ever grind one stationary spot. Doing so would overheat the metal in 5-10 seconds, and if this happens the blade will never be able to keep an edge again.
The very high disc speed can throw a knife if held to the disc in the wrong direction. Always confirm the direction of rotation before use (eg with a match etc), and take care to hold the knife the right way.
Always use indirect vent goggles, ear defenders, and ideally a full face mask too.
Never use a damp grit disc in an angle grinder, and don't dip cutlery in water to cool it when using such a disc. Damp grit discs can fail violently.
Keep your face out of the plane of rotation of the disc. Grit discs can break violently.
Angle grinder grit discs are somewhat coarse. This coarseness limits the level of sharpness available, but the result is plenty sharp enough for any normal kitchen use. It would not satisfy most die hard knife sharpeners though. Use only the very lightest pressure to achieve the sharpest edge.
Don't use these tools if tired, drunk, drugged, or not really with it. They aren't a nice friendly power tool.
====Use==== If you have an angle grinder stand, use it. If not, the tool may be held on its back to minimise fatigue. Sitting down with it on your knees (in your hand of course) makes it easy to pass knives both ways. However you position it, keep a good firm grip at all times.
To sharpen, move the blade as shown past the disc. Use the lightest of pressure only. 2 strokes on each side of the blade is enough for any blade that already has an edge formed, ie doesn't need stock removal. Finally make a burr removing pass along the other side of the blade (compared to the previous stroke). Use all the pressure of a feather, so the blade only just barely touches the disc.
Stock removal requires just a little pressure, and more passes. Never get the metal hot though, if in any doubt just put the knife down and come back to it a bit later. Dipping the knife in water is not recommended with grit discs, damp can cause violent disc failure.
===Die grinder===
==After grinding== Knives should always be washed after grinding. Grind stones can harbour all sorts of detritus, oil residues, decayed food & so on.
Its also worth warning the rest of the household if previously blunt knives are now psychopathically sharp.
==Care of sharp knives== Use of 30 degree knives on glass chopping boards or ceramic plates blunts them quickly. Most knife sharpeners prefer wooden chopping boards.
Knives with relatively soft steel benefit from use of a steel between sharpenings.
==Still to do== Stainful steel: pre-ss knives are occasionally seen, but I know nothing about their sharpening characteristics.
==See Also==
- [[Knives]]
- [[Special:Allpages|Wiki Contents]]
- [[Special:Categories|Wiki Subject Categories]]
[[Category: [[Category: