The No Bull Zone

Myth 1:  “Butchers, chefs, knife sharpening (grinding) services, etc, are knife sharpening experts”

• Most people (including journalists who don’t know us) turn to these ‘experts’ to find out about knife sharpening. Problem is, the same old stories have been passed down through the generations, by the same people, only because they seem to fit the evidence. Most have no basis in science, and many are just plain incorrect and confusing.
• Chefs do not make good knife designers, trust me, I’ve seen the same mistakes many times over the years. Mechanical Engineers need to observe what chefs do, then use specialized knowledge and research to come up with new solutions, which will then be appreciated by chefs. It takes an engineering degree and years of primary research to really understand what is going on with knife materials, cutting edges, manufacturing, handle physics, etc, believe it or not.
• With some knowledge of the science behind knives and sharpening, everyone can achieve better results, more quickly, with less damage to their knives and themselves. That’s what I hope to achieve with my R&D, the website in general, and this section in particular.

Myth 2: “Honing on a Steel only ‘straightens’ or ‘aligns’ the edge or burr”

• This is only true of the specific edge shapes that ‘burr’ – only for very finely angled edge bevels of around less than 10 degrees each side.
• These edges are rare, and only found on the finest slicing/carving knives.
• Most knives found in home and restaurant kitchens, or on sporting knives, have edges of greater than 15 degrees each side, and these edges are all simply too strong to fold over and burr. Edges feel dull simply because the fine ‘teeth’ on the edge have eroded, not because the edge has folded over, or ‘burred’.
• Honing is simply a process of laying new small scratches over the surface of the edge bevels, creating a sharp new ‘microserration’ on the very cutting edge, and this has nothing to do with a burr or aligning the edge, for any knife sharpened to greater than 10 degrees each side (99% of knives).

Human angle error during honing on a Steel leads to the profile shown in red. This rounded material must be removed to ideally return to new bevels of about 20º each side (blue lines). Most grinding methods remove far too much metal (yellow lines).	I took this micrograph looking side-on at a chef knife edge (200x magnification, diamond honed). The fine cutting edge ‘B’ is strong and well-shaped (flat bevel, no wear). Note the scratches across the bevel, which meet at the edge to form a fine ‘microserration’. This is really what honing is about: laying new scratches over the bevel to create sharp new teeth.	A closer look (2,000x) at the same cutting edge after 6000 cutting strokes (on a wear testing machine I developed). Note that the edge hasn’t ‘rolled’ or ‘burred’ during cutting, because it is too thick and strong. The edge is dull, because the ‘teeth’ on the edge have eroded and are simply less effective at cutting.
This finer-angled edge is sharper, but also weaker than the chefs knife edge. The red ‘burr’ is the folded thin edge, and this needs to be ‘re-aligned’ or ‘straightened’ (bent back to centre). This is where the myth started.	Side view of a fine slicing edge before wear (200x). The edge bevel, ‘D’, is at about 10º. Note some fine edge damage from the Steel and normal handling, which has created small burrs on the weak edge.	Looking closer at the same edge after 6000 cutting strokes (2000x magnification). Note how the thin edge has ‘rolled over’. This is what butchers refer to as the ‘burr’ that needs ‘straightening’, because the rolled edge is not sharp at this stage of damage. This ‘rolling’ will only happen to a very narrow edge, not to the broader edges typical of Chef knives.

Myth 3: “Chefs and butchers are good at sharpening knives, but most other people are just bad at it”

• Chefs and butchers look impressive with their rapid ‘swashbuckling’ swiping on a Steel, but their angle error every swipe is so great that they quickly ‘round off’ the cutting edge (in cross-section), to such an extent that the Steel no longer works and the edge is very dull and needs regrinding (back to flat-sided bevels).
• I couldn’t tell you how many times I’ve seen this at trade shows:
  • Chef or butcher who doesn’t know Füri walks up to our sharpening tools, and declares that they will show us how to hone on a Steel.
  • They pick up a demo Steel (we always have one there to show what not to do) and proceed to swipe furiously at it with a smug glow of superiority on their face….
  • ….until I point out the scratches all down the side of the blade, which clearly indicates that some of their swipes were at zero degrees (blade flat against the side of the Steel)! I also assure them that each of their other swipes probably varied between zero and 40 degrees, when a robot, or our simple Füri fingers honing technology, will always achieve 20 degrees every swipe. The reason they have to regrind their knives so often is that they (no human) can control the angles accurately enough on a Steel to avoid totally rounding off the edge to the point that it needs regrinding.
  • The clever, learning types stick around to ask intelligent questions, advance their knowledge, and switch to our sharpening tools.
  • The others storm off in indignation that a researching engineer claims to know more than them on this topic. Good fun, even though I know my debating partner is ‘under-gunned’!
• They will rarely tell you, but chefs and butchers also regularly need to have their edge bevels reground (on a stone, with a lot of time and skill, or by a sharpening service with lots of metal loss), to remove all the rounded edge metal from all the damage they caused by honing on a Steel.

Myth 4: “When buying a knife, if it feels comfortable in your hand and well balanced, it should be a good knife for you”

• This is an okay test for knives used for a few minutes at a time to rough chop for the occasional evening meal, but not good enough for professional or heavy knife users, because it does not replicate how you really operate a knife.
• This common advice doesn’t test for the hand strain that can be caused by too much squeezing on a badly designed handle shape.
• This test only measures ‘static’ comfort of a handle, and doesn’t test the performance of a handle under the repetitive ‘push down and forward to cut, roll through, lift back’ cutting motion most commonly used by chefs (a ‘dynamic’ situation, not well understood by Reps or retailers).
• The only way to test a handle’s performance in a store is to grip the handle in the normal way, safely hold the blade with the other hand (ensure edge is covered and hold from spine side), and push forward with the ‘handle hand’.
• The handle that best resists hand slip toward the blade will generate the least hand strain in actual service.
• The handle that shows the most slip toward the blade will generate the greatest strain, because the hand will automatically squeeze tighter on a slippery handle to prevent the hand slipping forward onto the blade. This is very fatiguing over long cutting sessions, and seriously damaging to hands over years of such repetition. There is a direct relationship between this test and the hand strain that the knife handle will cause.
• Choose a knife handle that best resists forward slip with the above test, and it will simply be the least fatiguing.
• My patented ‘reverse wedge’ handle shape will resist hand slip toward the blade better than any traditional handle shape, because traditional handle shapes for 800 years have had a taper down toward the blade (thick in the tail, thinner toward the blade), which actually encourages hand creep toward the blade.
• Balance is only important for the large knives that are used for heavy repetitive work in a classic rocking-sawing motion. Test the knife for balance at the point where the forefinger normally rests (in the curve of the bolster where the handle meets the blade, not behind the bolster on the handle). The knife should either balance evenly, or tip forward slightly, not tip back (slightly blade-heavy, but not handle-heavy).
• My Coppertail innovation (patents pending at time of writing) is for rebalancing knives as the blade is worn down (becomes lighter) over the years. Simply grind off some copper to rebalance the knife, and it will feel like a new knife again.

Chefs push down and forward for all their heavy cuts, so the hand is always creeping toward the blade. If the handle is also tapering down toward the blade, it takes more hand squeeze to avoid slipping. This squeezing is automatic: the brain will compensate for slip by telling your hand to squeeze. For chefs, this squeezing leads to fatigue, and strain-related injuries like arthritis and carpal tunnel.

For 800 years, western chefs knives have all used this handle shape. Modern stylish variations, like the handle at left, mostly have the same overall taper down thinner toward the blade.

This handle was developed by mechanical  engineers using sound principles of physics to resist hand slip toward the blade. The handle tapers in a direction opposite to traditional handles and most modern ‘designer’ knives. This ‘reverse wedge’ handle actively reduces hand squeeze required during heavy ‘push’ cutting, because the wedge locks on to the hand more effectively than a handle with an opposite (traditional) wedge.

A mirror image of the traditional handle at top reveals the origin of this shape: the first (Western) chef knife makers were sword makers in the 12th and 13th centuries in London & Sheffield (England), Thiers (France), and Solingen (Germany), and they simply adapted their common sword handle. With modern chef training, the pushing/rocking cutting motion now puts more strain on the hand, because the hand squeezes the handle tighter to avoid slipping forward down the wedge.

Myth 5: “Some knives stay sharp forever and never need resharpening”

• This cannot be true: where there is friction there is wear.
• Such claims should be more truthfully stated: ‘These knives cannot be resharpened and should be discarded when dull’.
• Such claims are sometimes made for cheap serrated knives, or hard-coated knives, which will stay sharp for a reasonable length of time, but they can’t be resharpened. These knives are not used by chefs because they are too coarse (tearing through the food instead of finely slicing).

Myth 6: “Stainless steel professional knives should never rust, because it’s the same material as my pots, forks and spoons, and they never rust, even in dishwashers”

• The material used in professional knives is very different to that used in sinks, pots and pans, forks and spoons, etc.
• The composition (mixture of material elements) and heat treatment required to harden professional knives also makes them less corrosion resistant. It is a balancing act for metallurgists to achieve long-lasting edge properties and stain resistance.
• To avoid isolated rust spots, simply wash and dry your knives after each use. Don't leave them wet on the sink, and certainly don't put them in the dishwasher. Dishwasher solutions are very corrosive, and eat enough material off your knife to 'round' the cutting edges; microscopically, but enough to turn a very sharp knife into just a reasonably sharp knife (the heat of the dishwashing cycle has no effect, contrary to popular belief).
• If your knives do get small rust spots, simply polish them off with a scouring pad (or cloth and metal polish), using only width-wise strokes across the blade. Don’t rub along the blade lengthwise, as this is sideways to the factory grind and scratches will immediately appear along the blade (even coarse scouring widthwise won’t show scratching because the blade is already ‘scratched’ uniformly in this direction during finish grinding).

Myth 7: “Thin Japanese knives have 15 or 17 degree bevels each side, and should be maintained like this”

• This is a common myth perpetuated by sales Reps for importers of these knives. The edges are thin and hand-finished to a concave (slightly rounded) edge shape, and are very sharp when new. However, it will be virtually impossible for the average user to maintain this original edge shape through manual or gadget methods.
• You are much better off converting these blades to exactly 20 degrees each side, with perfectly flat edge bevels, using the Füri Tech Edge or Ozitech sharpener/honers. The Füri edge has the advantage of being stronger than narrower-angled edges, while still being very sharp.
• My research into all kinds of edge shapes and finishes eventually led me to the conclusion that this edge shape is the best combination of sharpness and strength and, most importantly, this ‘Füri edge’ can be maintained extremely sharp, indefinitely, with very little skill and effort.

Other interesting knife myths and answers, in brief:

• M: “The best quality knives are fully forged, with a full-length tang through the middle of the handle, and 3 rivets”
• A: This is an archaic, obsolete, manufacturing method. Only the most expensive knives of this type don’t suffer from durability problems like loosening rivets, melting/cracking handles, and hygiene problems from food trapped in seams.

• M: “The old German knife factories are still the best at making knives and have the most knife engineering knowledge”
• A: Our success is proof that new technologies can overtake old, even in a very traditional industry, once the new is tried alongside the old. Most chefs stick with our products after trying them.

• M: “Country of manufacture is a good indication of quality and performance.”
• A: Not any more. Superior design and the same materials produced to high quality in China will outperform old technology made at high cost in high labour countries. High-cost countries either keep increasing prices, or reduce the materials and manufacturing quality to remain at competitive price. Neither is a good outcome for customers.

• M: “Damascus blades (folded into many layers) are superior to ‘regular’ steel”
• A: With modern alloys, equivalent, or superior, blade properties are achieved. Damascus-look blades are mostly a cosmetic treatment that only adds visual appeal.

• M: “It isn’t difficult to make high performance professional knives, and big cookware companies and most importers do sell good professional knives”
• A: I haven’t yet seen a real high-performance knife come from the marketing extension of a cookware brand, or from an importer of ‘generic’ knives sourced at the Asian trade fairs. It is much more difficult than the importer/marketers imagine to create a knife that will be respected and really used by the working chefs. None yet have really understood handle physics, blade and edge shapes and hones, and new construction alternatives.

• M: “Price is a good indication of not only manufacturing and materials quality, but performance”
• A: This is easy: simply compare our prices to the expensive older brands that don’t perform nearly as well!

• M: “Electric knife sharpeners can produce professional results and are accepted by expert chefs.”
• A: I have seen very few real chefs use an electric sharpener, and none outside of the USA. They can create an acceptably sharp edge, if carefully operated, but they usually remove far too much metal, and don’t create an edge that replicates the real honed finish of a Steel.

• M: “Knife grinding services don’t remove too much blade material and should be used whenever honing on a Steel stops working, because a stone takes too much skill and time.”
• A: Partly true (the last part)!

• A stone does take a lot of skill and a lot of time, but our Füri Edge Restorer (stage 1 of the Füri Tech Edge system) removes the minimum of material, and completely restores perfect 20 degree bevels, in under a minute, with no skill.
• Unless you have a good recommendation and have seen the work of a professional sharpening service, simply don’t risk it with your good knives. The best ones remove minimal metal, and are great for total blade reconstructions (broken tips, bolster thinning, huge chips, etc), but most remove far too much metal when only a simple bevel restoration was necessary (which shouldn’t actually reduce the width of the blade when done correctly). It all comes down to human error and skill, and your average saw, lawnmower blade and chainsaw sharpening guy doesn’t have the experience or finesse to look after a fine professional knife. There are a very few who are good, but seek them out carefully…..
  
  

Customer Feedback

From: David Corby
Sent: Tuesday, 18 September 2007 8:45 AM
To: info@furitechnics.com
Subject: Good Sense Well Written

Hi Guys 

I just read your No Bull section and I can finally rest happy knowing that there are people in the world who willing to bust all the common myths that you list. I am the manager of a Cook shop in Saffron Walden, Essex, UK, currently holder of the title 'Independent Cook shop of the Year'. For myself I held the title of Housewares Retail Employee of the Year 2005. Knives are my specialty, in my last store we displayed over 300 blades in a my custom designed room with a big empty table in the middle to lay out knives and to teach sharpening. I have lost count of the number of Muppet chefs who have tried to teach me how they use a steel, its always a good laugh to watch them go at it!

Brutal experience of running a sharpening service has taught me just how badly some folks treat their knives and how many dumb ideas they have about what constitutes good sharpening. I believe that TV chefs are mostly to blame. They give their knives a couple of fast flamboyant strokes on the steel, direct into camera and then start working with a with a brand new knife. No wonder most consumers think that a couple of violent strikes on a steel leads to a sharp edge. I have had customers bring me their 'razor sharp' knives to show off who become quite indignant when I point out just how blunt the thing is and then return it properly sharpened.

You are quite correct, knife sharpening is a specialist skill, I began learning at school in metalwork, yet it took another 18 years of selling knives and cookware before I was confident that my knowledge was sufficient to provide a top quality sharpening service. Your sharpeners are by far the best ones on the market and have become an instant best seller in my store. I can sell one of these to even the most unskilled customer, safe in knowledge that they will end up with a top class result.

Keep up the good work, there are a lot of knife users with a lot still to learn 

Your Sincerely

David Corby