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sharpening: holding angle from heel to point

post #1 of 9
Thread Starter 

Forgive me if I screw up some of the terminology.

 

So I've been practicing my sharpening for a few weeks and I was going to use the "coin tip" from this website to just provide a spot check that I'm pretty close to the angle that I want.  http://www.chadwrites.com/knife-sharpening-coin-trick-magic-angle-finder/

 

 

To make a long story short, if you want a 15* angle you divide the height of your knife by 4 and then the spine of the knife should be that height off the stone.  I'm an engineer, I'm sorry, my brain works well with math  :)

 

 

 

Anyways, as we all know, a common gyuto style knife is shaped somewhat like a triangle and the blade height reduces from the heel to the center of the knife to the tip of the knife.  So in order to keep the angle at 15* when I get close to the tip the blade is going to be lying flatter and flatter to the stone, correct?

 

 

Also, does anyone have any advice for sharpening the tip?  This has proved to be the most difficult part of sharpening for me, I've had quite a few times where I've dug the tip into my stone.

post #2 of 9

It's very easy to round over tips when sharpening. The general advice is to just start at the tip and stroke to the base.

 

As you learn control you can use the more traditional base to tip stroke. Both work. It's about developing muscle memory mostly.

Palace of the Brine -- "I hear the droning in the shrine of the sea monkeys." Saltair
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Palace of the Brine -- "I hear the droning in the shrine of the sea monkeys." Saltair
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post #3 of 9

If you're having trouble gouging the stone with the tip, try doing just edge trailing strokes with the tip.  With a bit of practice this will help you "feel" where the edge is without messing up your stone.

"Excellence is an art won by training and habituation. We do not act rightly because we have virtue or excellence, but we rather have those because we have acted rightly. We are what we repeatedly do. Excellence, then, is not an act but a habit." - Aristotle
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"Excellence is an art won by training and habituation. We do not act rightly because we have virtue or excellence, but we rather have those because we have acted rightly. We are what we repeatedly do. Excellence, then, is not an act but a habit." - Aristotle
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post #4 of 9

The Coin Trick absolutely will not work to keep a consistent angle.  If you (a) took trig, and (b) are looking at your knife, I shouldn't have to explain, but...  A constant distance from spine to stone will create an edge angle which varies proportionally to the variance in distance from spine to edge (which varies a lot at the tip where the "lower limit" is zero).

 

The easiest way to teach yourself a given angle is to draw the same large angle on several pieces of graph paper and put them around your sharpening station where you can compare.  You won't be perfect, just do your best.  Use the Magic Marker Trick to make sure your bevel shoulder runs in a straight line down the length of the knife.

 

As they approach the tip, most freehanders lift the handle a little to keep the tip on the stone.  This tends to sharpen the tip area at a slightly more acute bevel angle, and you'll almost always see a wider bevel at the tip on hand sharpened knives.  For your part, lift the handle as necessary and try for consistency.  Again, the MMT is your friend. 

 

You can use heel to tip strokes edge leading or edge trailing.  You can go back and forth up and down the stone.  You can also section with any or all of those three different strokes. One doesn't work better than any other generally, although one may prove more comfortable or consistent for you.

 

It's not a general truth, but in my experience most good sharpeners tend to section the tip during the burr creation process, at least somewhat, in order to make ensure (again) the tip was actually on the stone and that the burr was formed.  Use the MMT, plus one of the burr thumb tests to make sure.

 

Using edge trailing strokes tends to draw out the burr more; while edge leading strokes tend to dissolve it -- somewhat.  If you use anything other than very light pressure and very few strokes with an edge trailing (called "stropping") only motion, you really should deburr before moving on to the next highest grit. 

 

BDL

post #5 of 9

Trying to force yourself to maintain an exact angle never works well to produce a consistent angle from heel to tip. Once you established what the advised approximative angle should be, using any trick or calculation, put your knife on the stone and forget about the exact angle. Just let your mind take over and sharpen the entire knife. Not one professional or amateur freehand sharpener has an idea which exact angle they produce, none! Just stick to the angle your body dictates, it works best and allows you to focus on the whole concept of the sharpening.

 

I do agree that sharpening the tip is quite difficult. I never sharpen the tip area (let's say 2 inches) in sequences as it will eventually flatten out the curve in that tip area.

When sharpening the tip area, I keep my "free" index finger on the bladeside, on a point at around 1 inch from the tip, and use that as a "pivoting point". Meaning that I constantly change the position of the knife relative to the stone using my pivoting point. I vary the position of the knife randomly from a 90° relative position to almost parallel to the stone, but I keep the knife at the same time going up and down the stone, keeping my indexfinger constantly with almost no pressure at my pivoting point.

When sharpening the ultimate tip area (let's say the first 5 mm from the tip), I put the knife almost parallel to the stone, use the same "pivoting point" with very little pressure and now slide the tip as little as 10 mm up and down the stone while constantly reducing the sharpening angle by merely a few millimeter and back.

post #6 of 9

Unless I missed something, the thing the "Magic Coin Trick" seems to have left out is the thickness of the spine. For example, in many cases the spine of a forged blade is going to be a good deal thicker than that of a stamped one. The thickness of the spine is going to affect the final angle at the edge considerably, unless you are somehow measuring to the middle of the spine rather than the edge.

 

Regarding learning to sharpen, I highly recommend Murray Carter of Carter Cutlery. He is a master bladesmith, and as well as forging blades has made some instructional videos. Here he sharpens a blade using a cinderblock, a 2x4, and some cardboard: http://www.youtube.com/watch?v=CXLaE1JvQ94

 

There really is no mechanical guide to help you get the correct angle on the edge of the blade, (as you seem to have already surmised) as none of them can account for and adapt to all the different shapes and lengths of blades.

 

 

("I used to not even be able to spell 'eng-in-ear,' but now I are one")

 

 

post #7 of 9

Corny,

 

Funny thing, Murray Carter teaches the coin trick.  So does Chad Ward. 

 

The width of the spine is not a big source of error with the coin trick.  The coin trick assumes the bottom of the spine (on each side) and not the center, and always (by necessity) measures from the bottom face of the knife at the spine.  Thus it measures the edge angle on each side of the knife without any error inherent from "guesstimating" the spine's center.    

 

If you understand sharpening, you know the goal is not to create the desired angle perfectly, but to create an edge which is consistently close.  The coin trick isn't a bad way to establishing a new edge angle on a knife at the heel.  After sectioning the first stone-width though, it's a misleading distraction.  And for returning to an established angle, it's not as good as "clicking in." 

 

I don't like the coin trick myself, but there other things besides spine width making it problematic.  Its highly dependent on placing the stack of coins and the knife in exactly the same position ever time, which is another way of saying you can only reproduce the desired angle from that one position.  Get the spine a little off the edge or the center of the coin (whichever you've chosen), and you've shortened the base and hypotenuse, while decreasing the height.  Furthermore, at ~0.07" width, a quarter isn't what you'd call a precise tool in finding a very specific angle within plus or minus 1*.  Take those two together, and you can see what I mean about "misleading." 

 

A stack of 7 quarters (typical stack size) has a way of falling over with very little provocation.  So on top of its other shortcomings, the coin trick is a PITA.

 

More generally, I feel it's a mistake to try and pursue precise angles too ardently, since you'll never really achieve them; just as it's a mistake not to "do your best," to find and hold whatever is optimal for your knife. 

 

It's attractive to a certain mind set though, that is one which prefers the security of apparently objective, external measurements, to measurements taken by touch (like clicking in) and by eye.  At the end of the day, good freehand sharpening is going to depend almost entirely on how well you train your wrist and the techniques like the coin trick are mostly ways of getting started on that. Other ways, such as referring to large pictures of the desired angle, work just as well. 

 

Done right, sharpening is a practical discipline acting as a handmaiden to something else, like cooking.  It's neither an exact science nor an end in itself.  The best you can do is bring some experience and perspective to the task.

 

Bottom line:  Whatever works.

 

BDL

 

PS.  You've said some very interesting things in the short time you've been on CT.  Welcome!


Edited by boar_d_laze - 10/29/11 at 10:52pm
post #8 of 9

Not sure if the following will allow for an exacting conclusion, but being a bit analytical myself I had found the lack of ability to confirm complete uniformity of the blade angle to the stone somewhat confusing and maybe even frustrating when first learning to sharpen.

 

One thing that helped a whole lot (yes a big ole bunch lol) was to accept that freehand sharpening was sort of a combination of both math (determining the proper angle to hold the edge to the stone etc) and art (the ability of the sharpener to change the effect of the angle applied across the knife edge).

 

So though you can initially set the starting angle at most any point along the edge except the tip area which will calm typical thinking of any engineer (coin trick or other method) you still are going to need to accept that as you progress towards the tip (or more of the blade if you use a side to side technique) you have to release the thinking of an engineer and allow your inner artist to come to life.

 

Actually I think this is the more enjoyable part of freehand sharpening as it really does allow a bit of self expression, and like a painting or sculpture etc each time a bit different and really part of the sharpener.

 

It can be fun, and I remember feeling that it was similar to how a really good architect (not just the average) can combine math and design to achieve a superior result.

 

It really is much more than just hard set numbers.

 

 

"love my country" but "fear my government"  Something is just wrong with this

 

 

 

Looking for info on entry level J-knives? Need help on finding the most bang for your buck? Hope you enjoy learning from the info here, I know I did!

http://www.cheftalk.com/t/63213/tojiro-dp-f-809-240mm-g...

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"love my country" but "fear my government"  Something is just wrong with this

 

 

 

Looking for info on entry level J-knives? Need help on finding the most bang for your buck? Hope you enjoy learning from the info here, I know I did!

http://www.cheftalk.com/t/63213/tojiro-dp-f-809-240mm-g...

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post #9 of 9
Thread Starter 

I watched a few more videos and focused on tip sharpening and I'm doing much better now.

 


I do think the coin trick is servicable for noobies to make sure you are relatively close to the angle you are after.  Maybe even a good spot check for moderately experienced sharpeners who might stray or develop bad habits over time.  At least for the heel and perhaps up to 60% of the blade, which for me, is where most of the cutting takes place anyways, the coin trick works just fine.  I think this mindset of going japanese and having more acute angles lead me to guess a fair bit too acute when I started.  I think I'm much closer to 15* now and I can feel the difference.  For my purposes less than 15* isn't worth it. 

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