Angle Mismatch between KS-123 and WM-200

[tgbto]

If that's of any help to you, the "Top-of-USB to wheel" distance depends on wheel size and projection distance only. It doesn't change with the position of the MB-102.

[BlueDun]

If that's of any help to you, the "Top-of-USB to wheel" distance depends on wheel size and projection distance only. It doesn't change with the position of the MB-102.

Good point - thanks!

[RickKrung]

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.

I do not agree with the bolded statement above, IF one uses the distance from the USB to the wheel surface - rather than making all those distance measurements.  If using the distance to the wheel, that is the only measurement that is used, which reduces the measurement cumulative errors.  Using that one measurement makes varying positions of the MB-102 (or FVB) and USB irrelevant.

[Ken S]

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

Bluedun,


You have outlined an impressive workflow. If you plan to operate a sharpening business, how much would you charge a customer to sharpen a knife following your workflow?

I would not say that this workflow is impractical, only that it seems best suited to high quality, low volume sharpening. I would recommend you also formulate simpler, lower cost options. Reserve your procedure for your personal knives and for those people who really appreciate fine edges.

Ken

[BlueDun]

You have outlined an impressive workflow.

Naaah ... I'm just an engineer suffering from professional deformation 

I would not say that this workflow is impractical, only that it seems best suited to high quality, low volume sharpening. I would recommend you also formulate simpler, lower cost options. Reserve your procedure for your personal knives and for those people who really appreciate fine edges.

I sharpen for myself and very rarely for a good friend. No need to optimize economic efficiency.
I sharpen because I'm lost to the ZEN-effect of it.
You guys know what I mean ...

[Ken S]

Ah ha! A good post gives me information; a great post gives me information and a good chuckle! When I started on the forum, Jeff Farris, the forum founder and previous moderator, and I shared a running joke. "How many angels can dance on the head of a pin?" Fortunately the forum has no Inquisition, so no members were harmed.

Seriously, I am glad we have some engineering types on the forum. Wee have all benefitted from the "professional deformation".

Ken

[3D Anvil]

I've been using the KS-123 for a few months, after a couple years using the calculator method, measuring to the top of the case.  I find the two methods equally accurate (to within about .5°), measured using a laser goniometer. In other words, .5° is the maximum divergence I've seen.  On average I'd say the set angle is coming in within 1/4° of the actual angle.

For the most accurate results with the KS-123, I find that I do have to recheck the angle after tightening down the USB.  Even though I push down on the USB when tightening, I generally get a +0.5° shift.

[BlueDun]

@3D Anvil : That is a valuable piece of information as far as I am concerned. Thanks 👍

[Drilon]

Hi Enrico,

there must be a difference in the angle readings because you are measuring in two different planes.

With the WM-200 you measure along the side "b", with the KS-123 along the central tangent line.

For example, on a Global knife, I measured the thickness of the spine to be 1.2 mm, so "a" is 0.6 mm. The value for "b" is 20 mm.

The angle for the difference of the planes is calculated with the formula
angle= arctan (opposite "a" divided by adjacent "b"), 
with the given values
arctan (0.6/20) = arctan (0.03) = 0.0299910049 rad, converted to degrees gives 1.72°.

If you want to get an angle of 15°, set KS-123 to 15°, but set WM-200 to 16.72° (it will be difficult to be that precise!!).

Hope this helps.

Regards,
Drilon

[Drilon]

Here is the file

[BlueDun]

Hi Werner

Danke für den Hinweis und die Ausführungen.
Den Klingenwinkel hatte ich schon auch auf dem Radar. Er erklärt aber einfach nur einen Teil der Abweichung von 3-4 Grad. Ich denke, beim WM-200 summieren sich einfach eine Reihe von systematischen und zufälligen Fehlern und daher ist es für Messer eher ein "Schätzmittel" und kein Messmitel 

[Ken S]

English translation of last reply:

Thank you for the hint and the explanations.

I already had the blade angle on the radar. But it just explains part of the deviation of 3-4 degrees. I think the WM-200 simply adds up a number of systematic and random errors and therefore it is more of an "estimate" for knives and not a measuring device.