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[measure]

When I hear concerns about using the KS-123 due to it being less than needed accuracy, I wonder why the angle on the blade must be accurate to 0.1°.  In the sharpening I do for most things, if the angle is good to +/- 1 degree I am good.  What am I missing?

Nothing.

I think this is an example of going to the extreme without any clear delineation of the benifit. When Wootz proposed some new idea he backed it up with extensive testing and real world usage in meat packing plants. I believe only a miniscule number of users have the ability to measure the angle to this accuracy.

If I may introduce a modicum of nuance and open-mindedness to "Nothing" :
- I agree being able to measure the edge angle with 0.1° precision has no benefit in terms of sharpness or edge retention
- However, being able to reproduce a given angle quickly with the smallest deviation possible results in raising a burr much faster, with less metal removal.

As we are talking small angles, the amount of metal being removed is proportional to the ratio of angles : you remove 5 times more metal if you're 1° off compared with .2° off. It is to me a clear delineation of the benefit. [EDIT] Actually, much more than this if you take into account cases where you will be thinning the blade [/EDIT]

There are two phenomena with hysteresis here :

- One linked to the threaded rods, which can be compensated by always ending with slightly raising the USB. This is standard operation and does not cause any issue. It will prevent the USB from settling lower due to the rod moving slightly insided the nut before getting fastened.

- Another one linked to friction inside the KS-123. Going down, then up, will ensure that the error is always on the same side. For a given static friction coefficient, that is, which will depend on when it was lubricated, if it is slightly wet or not, how tight the nut is, etc. Plus, the amplitude of USB movement necessary to put the needle back in motion on the way up is much, much higher than with vernier calipers resting against the top of the USB and the wheel where only the slightest turn of MicroAdjust nut is enought to lift the lower end of the wheel.

So while using the down-then-up routine will minimize the error, it will still be more important than using the distance method, less reproducible, and therefore the amount of material that needs to be removed before raising a burr will statistically increase.

the KS-123 has significant hysteresis

I have not noticed any.

Do you mean that says, one 8th of a turn on the MicroAdjust always results in the plastic needle moving on the KS-123 ? On mine, even after some lubrication, if I move the USB down, then up, I can change the angle by almost 3/4th of a degree before the needle starts moving up again. And I can move the needle up and down by hand, the flexibility and friction will let it stay wherever I put it within one degree.

[...] the KS-123, which has halted the growth of computer programs and all communication about it.

What a relief, more focus on the real work.

Wow, that's a tad judgmental. There are very good apps out there, and the KS-123 has significant hysteresis. Surely there is room for people who already own vernier calipers and are fine with using apps/spreadsheets ? Why the condescension ?

While I have occasionally experimented with 12°, based on Wootz' recommendation, 15° has remained my go to setting.

Same here. 12 dps is for a very specific subset of knives : suisin inox honyaki series knives whose steel is quite robust, or some of my high hardness knives. The problem with 12dps in my opinion is that although edge retention is usually better, the apex is prone to chipping. So it's only for knives that are going to be handled carefully.

As chipping is much less of an issue at 15dps, I feel this is the good compromise with good edge retention.

As a side note, when one is not concerned with initial efficiency, I find that a 10dps primary bevel with a 15dps secondary bevel works wonders as it allows for very quick touchups afterwards.

I used to sharpen @20dps a long time ago. Then I came across Wootz's litterature and decided to give 15dps a try.

It has been my standard since. I made comparisons using the same knife model sharpened at 20 dps and 15dps, the 20 dps got dull significantly faster. I have not noticed 15dps being too fragile for standard to fairly high quality knives.

For more details, you can read a piece I've written in my personal blog.

Hello Jamie,

I sincerely hope your presonal blog is not a collection of AI-written articles. Still, a couple of things would have me either believe the contrary or at least think you should cross-check what you present as definite truths.

A few examples amongst many :
- On your page about "hollow edge knives", what you are describing is not a hollow edge (the edge being the part that actually cuts the food, a hollow edge or concave edge is created by a convex sharpening medium such as a wheel). I suggest you quickly compute an estimate of the weight difference between a scalloped blade and a plain one, you'll see soon enough that there is no significant difference in knife weight. And... "I prefer chef knives because they're thick"? Really ? The "hollow" santoku you show is probably twice as thick as the thickest of my chef knives. The thicker the knife, the higher the resistance to cutting because of the effective surface.

- What you present on your article as a chef knife is actually a santoku, the chef knife being a gyutou instead. I  fail to see how a chef knife would be less able to handle mincing herbs than a utility knife. A chef knife, having a higher blade, allows for more control and consistency while mincing.

And there are countless others.

Well, actually it does look like AI slop. I'm not sure it does anyone a service, including yourself.

As a side note, you can also get an accurate value of this offset if you use one of the many calculators available (calcapp, tormekcalc, etc.) by both changing the diameter of the wheel to 254mm *and* reducing the distance to top of the wheel by 2mm.

The work being done can be measured by the material being removed (bonds being broken within the steel) and the generation of heat. You need to maximise the first and minimise the second. We want as little heat as possible and as much material removal as possible for maximum efficiency.

Agreed 100%.

To complement my response to OP's objection, the Higher MOH of the abrasive relative to the material being ground allows it to scratch said material. In doing so, there is resistance to the relative motion of the abrasive and the material. This resistance is precisely friction, and overcoming it generates heat (due to resistance to gliding at the molecular level AND to the the energy released by the breaking bonds within the material AND to the wear within the abrasive).

Lubricants work by separating surfaces. A lubricant that would work so well that there would be no resistance to the relative movement of the abrasive with respect to the ground material would also prevent the abrasive from scratching the material. For grinding to be effective, surfaces have to be allowed to come into contact. Where they come into contact, the kinetic friction coefficient depends only on the surfaces, not the lubricant.

Machinists know that a dry bit removes material much faster than a lubricated one. Unfortunately, it also breaks down so much faster that it is impractical to use it dry.

Water for the Tormek is a good compromise : it properly transfers heat away from the point of contact, lubricates a bit but still allows grinding to happen quickly enough.

TL/DR : the better the lubricant, the less abrasive and steel come into contact, the slower steel is being ground.

I apologize if this is a stupid question but, I was wondering if anyone knows the degree difference on the angle master setting of 250mm to the middle scale of 10"?

It's not stupid at all. If you play with the model here, you'll see that for a given setup (USB height set, projection distance set), the difference in angle when the stone diameter varies from 250 to 254mm is about 1 degree. So for a given position of the WM-200 on the wheel while resting on the flat of the blade, the angle read on the WM-200 should be off by the same amount.

This is patently false and a myth that needs to die. Friction is nothing more than generating heat.

Thank you for your kind, nuanced words.

Still, from a physics standpoint, in a situation where a solid moves in relationship to another, the friction coefficient is the ratio of the tangential force to the normal force. If there is no friction, there is no tangential force applied to the material being cut, so no work being done and obviously no matter being removed.

In the same fashion, a frictionless action of a knife blade on a tomato will press down on the tomato but not cut it. Our job as sharpeners is to make sure friction happens over such a tiny surface that the cells are instantly sheared in two by the focused tangential force without the tomato being deformed by the normal force.

Heat is a byproduct of friction, heat reduces cutting of abrasives, and increases wear ; hence the need to use a coolant in many situations where friction generates a lot of heat, or to reduce friction using a lubricant where the unlubricated action would generate more heat than the tool (drill/belt/wheel) or piece would be able to withstand locally. Cutting fluids act as both.

In my experience, the SG is okay for most stainless and carbon steels. Only carbide steels or one type of very scratch-resistant carbon steel require the SB or a diamond wheel. Could it be an issue with applying too much pressure on the wheel ?

If you reduce friction you will reduce sharpening efficiency. In another post, you seem to complain that the stone is glazed and needs refreshing... If the stone wears down it means that new abrasives are exposed, therefore maintaining sharpening efficiency. If the stone wears down too quickly, it means it is not hard enough for the material you're trying to sharpen.

I'd contact Tormek support.

Phil,

I'm not sure I understood properly, but I think what you're measuring with your AngleCube or such is the angle between the horizontal plane and the side of the blade.

The main part of the difference here is that the knife does not contact the wheel exactly at the top of the wheel. So to find the correct angle, you'd have to mark the radius of the wheel at which the apex of the knife makes contact, then measure the angle between this radius and the vertical, and subtract this angle from what you found previously (if the contact happens further away than the top of the wheel, which is usually the case).

You are also dealing with a lesser error : the blade is usually tapered, so the side of the blade is usually at an angle with the plane of symmetry of the blade. So you'd have to measure the taper angle : you can clamp the blade in a vise and take one measurement on each side, then divide the difference by two. Once you have this difference, you have to subtract it to the angle you read on the angle cube resting on the side of the blade.

For more on this, here is a link to a geogebra page I designed where you can easily play with this subject, no advanced mathematics involved. The first error is the angle between the dashed line (from the center of the wheel to the point of contact) and the vertical axis. Or the other dashed line (tangent to the wheel at the point of contact) and the horizontal axis.

Hope this helps !