Angle Mismatch between KS-123 and WM-200

[BlueDun]

Runnig a T-4.
I just got my KS-123 together with a new DE-200 diamond wheel. Started playing with the KS-123 and also tried to compare the angle reading of KS-123 with my ol' WM-200. And I find a consistent offset of about 3-4 degrees. Retried again and again, also with different knives (blade width). The WM-200 always reads a higher angle. E.g. if I set the angle to 15° with the KS-123, the WM-200 will read between 18° and 19°. If I set the KS-123 to 20°, the WM-200 will read between 23° and 24°.
Completely clueless .. any help highly appreciated - thanks

[Ken S]

Welcome to the forum, Enrico.

The short answer is that an exact reading in degrees doesn't matter. Consistency and repeatability are more important, both for cutting and for minimizing the amount of steel removed in sharpening.Exact measurement is more important when two surfaces are mated, such as in a threaded nut and bolt.

I suspect the difference you are reading may be caused by the taper of the blade. The WM-200 works very well with tools like chisels, with a large, flat measuring surface. The KS-123 is a substantial improvement for knife set up. Incidentally, whether your Tormek is a T4 or T8 makes no difference in this matter.



In our enthusiasm, it is easy to blur the line between practical precision and our egos. I do not wish to demean the pursuit of excellence; however, to borrow a line from one of the online classes, "the tomato doesn't know the difference".

Ken

[Sir Amwell]

Whilst I agree with practically all your points Ken there is a clarification to be made. If one is crossing from the Tormek to say a 1x30 leather belt in order to hone and say you want to increase the angle by half a degree as is common for some steels, you would want to be as precise as possible and be confident of your angles. A goniometer isn't always easy to read precisely and the sharpie method on a flexible leather belt won't tell enough.
But yes, my advice is stick with one (preferably the ks 123) and don't mix and match.

[Ken S]

You make some good points, Sir Amwell. My sharpening has been limited to Victorinox, Mora, and standard Buck knives. I would probably feel differently if I was investing in or sharpening super steel knives. My simple methods have worked for me. Others may find more sophisticated methods preferable, which is fine with me.

We both agree about the KS-123. I believe the WM-200 will continue to be useful for tools like chisels and plane irons. In the future, I see the KS-123 quickly replacing the WM-200 for knives. I also believe the black marker will continue to be useful.

Tormek is innovative and adaptable.

Ken

[BlueDun]

@Ken: Thanks for the kind welcome. Very much appreciated 👍
I hear you and I fully agree with you regarding the aspects of consistency and repeatability.
But Sir Amwell's objection is also valid and it is of relevance for my case. It's about the question if the indicated values of either tool are "true" values. And it is also about repeatability across tools that claim to output numeric measurements of physical values.

Why is this relevant for me? Well, I use my T-4 for knife sharpening only. And I own various kitchen knifes of European and Japanese make. Using my WM-200 so far, I did set the bevel of each knife according to knife and steel specs. This ranges from 14° for an ultra thin Nakiri up to 21° for my Wüsthof workhorse. And now I bought the KS-123 and I see that the two tools are not consistent in their readings of the sharpening angle.

The first issue now arises when I switch to using the new KS-123 as my standard. I cannot work with the values I've been using on the WM-200 to set the angle on the KS-123. This leaves me with two options. I can try and recalculate the correct value for the KS-123 with an offset based on the observed deviation. Bad idea in my opinion. I'm introducing an additional step in my workflow that is a source for errors – even more so as both of these manual tools do have limitations in their accuracy of measurement.
So I'm left with the option to properly re-set the bevel for each knife using the KS-123. But here it gets tricky because the observed difference of the tools made me aware that these tools do not show me the true value of the sharpening angle. At least one of them must be off. And because I do not own a goniometer I cannot verify the measurements and therefore I have to assume that both tools are not showing true values. And here it gets problematic. Especially with very narrow edges.

Let's take the Nakiri with a target angle of 14°. My observed difference between the WM-200 and the KS-123 is something like 3.5°. That is already an error of 25% with respect to the target value. And that is assuming that either one of the two tools is spot on the true value. But what if booth tools are off the true value in the same direction (i.e. both show a too large value)? In that case the error even increases. Not acceptable in order to put a suitable bevel to said Nakiri! So, right know I got two tools to measure my sharpening angle and I do not trust either one.

Apologies for the lengthy elaborations so far. I guess it boils down to two questions for me now.

1. Can my observed difference using the WM-200 and the KS-123 on (kitchen)knives be reproduced by other users as well? Or is the observer the problem due to his incompetence of tool handling? (BTW. I watched each and every instruction video and spent the whole afternoon yesterday trying to find the fault... but nobody is perfect)

2. Did anybody validate the correctness of the measurement with respect to true angle? I.e. by use of a goniometer.
Especially for the KS-123, as I want to use this from now on. But also the verification of the WM-200 would be interesting.
In other words, can I trust the values from the KS-123 or will I have to work with a correction offset to get my narrow knife angles correct?

Thanks for any feedback!

[BPalv]

I recently attempted to set 3 machines with 4 wheels at various settings to sharpen and differentialy hone.  I spent a lot of time jiggling and in general fussing with the KS-123 and never achieving the precise measurements or results I had hoped for.
I went back to the Calculator.
The angle setter vs. the calculator was more than 2 degrees off.  Could have been user error as I've only been using the calculator a couple years and new setting angles with the KS—123.
I think some of the issue to as Ken stated that it could be the way the knife sits in the 123.  I still see some benefit.  If you don't need to be exact, it will get you close.

[John_B]

It has been a long time since I used the WM-200 I may just get it out and try myself.

I think Tormek did considerable testing to insure that the KS-123 results matched those of the software bar height calculations. I believe members here also participated in the early testing.

[Ken S]

As I went to post my reply, I received the message that another reply had been posted. I am adding this to my original reply.

For many years, I have had a hobby interest in machine shop measuring. In the machine shop world, "exactly" is not used. Measurements are expressed in tolerances. Tolerances vary with the requirements of the work and are often included on the blueprints as + or -. The accuracy of measuring tools is often noted in precision tool catalogs. Expect to pay considerably more for tools with tighter tolerances.


Enrico,

I applaud your thoroughness! One of the reasons for my faith in the KS-123 came from sitting in on a meeting of the Tormek Innovation Committee in 2023. The committee included Håkan, Tormek's abrasives expert and retired CEO; Mats, the Head of Support and employee number six, with three decades of experience; and Tim. I did not know Tim prior to the meeting. He has a position in the technical design department. The other guest was Per, a retired industrial engineer. Per is a member of our forum and had designed a similar jig to the
KS-123. There was enough technical expertise in the room to light up the village!

I suspect the WM-200 was a carryover and originally designed for tools with a larger, flat measuring surface like chisels and plane irons. With these measuring surfaces, it performs very well. It does not do well with tapered knife blades with very narrow bevels.

As a stopgap measure, I designed and posted a substitute measuring target. When set for the same projection as the knife, being flat it performs better than the WM-200. It is no match for the KS-123.

Hopefully, other members who use theKS-123 witha goniometer will reply.

Ken

[tgbto]

Hello,

[TL/DR: Use a calculator and calipers if you want the most precise way of setting an angle]

The intrinsic flaw in using the AngleMaster for knives is described at length in posts such as this one or this other one. The design of the WM-200 offsets the measurement by exactly half the total taper angle of the blade. This is a systematic error that cannot be reduced by training, not by increasing measurement precision of wheel diameter, etc.

The KS-123 is based on a design that allows to measure directly the angle between the tangent to the stone at the point where the apex will sit and the axis of the sharpening jig (which coincides reasonably well with the plane of symmetry of the blade when using the KJ). So no such skew here.

Precision is a different matter. It can come from many things, from the size of the needle on the KS-123 to whether or not you put a light in just the right place when you use the AngleMaster, but also what tolerances cumulate in the construction of the devices, how reproducible the manufacturing process is, etc. etc. To have a substantiated answer to "how precise is the KS-123 ?", you'd need to get a statistically significant sample of jigs, and not only a goniometer but also a consistent way of setting up the tool before you take your measurement. Not sure it's going to happen.

My gut feeling is that the KS-123 has a precision of around 1dps when setting an angle, and probably a fraction of that when reproducing an angle that has been ground using the KS-123 in the first place if your setup process is consistent. In my opinion, the biggest source of error in using the KS-123 comes from the hysteresis/backlash due to the friction between the black plastic part and the metal body and the flexibility oof the plastic needle. It can be reduced with a tad of silicon grease, and consistency can be improved by always approaching the target angle from below by raising the support bar.

Using a calculator rids you of many of these imprecisions. Calipers can be adjusted precisely with very little hysteresis, and the values you use are large enough that a little error will only have a small impact on the result. Much smaller than if you sum the width of the needle with the typical hysteresis of the KS-123.

[Ken S]

We are missing two important pieces of data:
1) the tolerance range for bevel angles in various applications.
2) the accuracy tolerance of our measuring tools (both the KS-123 and the calipers)

Most companies do not publish this information. Most users do not have a sophisticated enough understanding to interpret this data. It would be helpful to the few of us users who have the knowledge and interest to do so.

I suggest starting with one of your knives which you have already sharpened at your ideal bevel angle using your WM-200. Using your black marker, carefully insert it in your KS-123. Adjust the KS-123 so that the angle setting matches the black marker. on an index card, note the information about the knife, the previous ideal angle, and the new angle with the KS-123.

You may want to do this with all the knives you regularly sharpen. The procedure does not take long and it is "one and done". Or, if you find a consistent pattern emerging after a few knives, you may just want to add the difference to your original readings.

Ken

[tgbto]

We are missing two important pieces of data:
1) the tolerance range for bevel angles in various applications.
2) the accuracy tolerance of our measuring tools (both the KS-123 and the calipers)

Right but... even cheap calipers such as those won't have an accuracy below .25mm. Which around 15 dps translates in a .2 dps accuracy. So whatever your tolerance on the result, you will get closer to it with a more accurate measurement principle.

Plus, whatever their accuracy, if you always use the same calipers, the end result will be more repeatable than with a tool with a rather wide, flexible needle, and noticeable hysteresis. Which in our world translates in less time to raise a burr.

[BlueDun]

Appreciate all feedback so far – cheers guys 👍

I think I settled on my way to skin my cat.

Status:
-   KS-123 is in the house
-   KS-123 differs from WM-200 in terms of angle readings
-   Absolute value readings questionable for both tools

Goals:
-   Want to ditch WM-200 and integrate KS-123 into my workflow

Consequence:
-   All my knives net to be set with new bevels

Principles & Assumptions:
-   Calculator method is the most precise method to set actual grinding angles. It's also the most reproducible at the cost of being somewhat cumbersome.
-   KS-123 is easy to handle and - with proper and careful handling -  sufficiently reproducible

Workflow:
-   Set the new bevel by means of the calculator method
-   Grind new bevel on grinding wheel
-   Use the KS-123 to "read out" the angle. That may differ from the calculated value.
     Note down "KS-123 angle" for each knife
-   Transfer to JS wheel and felt polishing wheel by use of KS-123. Quality control with microscope.
-   Future maintenance with KS-123

[tgbto]

That sounds good. Just make sure during the third step of your workflow that you find a way to account for hysteresis.

You could check if you made a good job of it by changing the setup of the KS-123, then reproduce the settings you just noted down, see if a new sharpie layer is properly removed.

Cheers,

Nick.

[Dan]

...

Principles & Assumptions:
-    Calculator method is the most precise method to set actual grinding angles. It's also the most reproducible at the cost of being somewhat cumbersome.
-    KS-123 is easy to handle and - with proper and careful handling -  sufficiently reproducible...

Just to add my two cents, I have to say that I find the calculator method (Calcapp by Cbwx34)

https://connect.calcapp.net/?app=3fp8xu#/

extremely easy, reliable and repeatable. This goes for knives and chisels, planes etc.
Each time I resharpen my knives, I set the angle very quickly to 15° with this and it is pretty much bang on from the previous sharpening.

I have not used the KS-123 so can't comment on that but I don't see any need personally, having the app is very easy.
It did take me a little moment to get used to using it but it is pretty straightforward.
Danny

[BlueDun]

Just to add my two cents, I have to say that I find the calculator method (Calcapp by Cbwx34)

https://connect.calcapp.net/?app=3fp8xu#/

extremely easy, reliable and repeatable.

Agree - but only as long as I stay on the Vertical USB.
I use the JS and the felt wheel edge trailing with HUSB/FUSB. And I don't keep my MB-102 fixed in its position. I play with its position depending on knife size for a comfortable handling and I remove it completely when I stow the the sharpening stuff away. Using the KS-123 to transfer the correct angle in that case is much more appealing than re-measuring and re-entering all distance values to the calculator.