Sharpening Calculations

[John_B]

We have seen a number of threads over the past months on calculations to set the USB height to achieve a specific grinding angle. I do not want to upset anyone with my questions but I am wondering what are the actual differences between the various methods presented? For someone that is sharpening knives using the Kenjig concept is there any practical difference? I have been using a single calculator and have not tried the different ones that have been presented and my edges have all seemed consistent and after honing exceptionally sharp.

[cbwx34]

We have seen a number of threads over the past months on calculations to set the USB height to achieve a specific grinding angle. I do not want to upset anyone with my questions but I am wondering what are the actual differences between the various methods presented? For someone that is sharpening knives using the Kenjig concept is there any practical difference? I have been using a single calculator and have not tried the different ones that have been presented and my edges have all seemed consistent and after honing exceptionally sharp.

The short answer, (that shouldn't upset anyone), there's no practical difference in the calculators talked about here in the forum, that measure to the wheel, (which is what the "Kenjig concept" does).

Since you're getting the results you want, stick with it... no practical difference, and no reason to change.  I also say, consistency matters too.

[Jan]

John,
full answer to your question would open the Pandora's box. Sometimes it is better not to open it because you can't close it again. 

Some calculators may cause an error of 1⁰ per side. When you are grinding a 15⁰ per side angle it will not strongly influence your results. When the error occurs also at the honing wheel set up it can influence the quality of some advanced deburring methods and increase the BESS score.

When a knife maker grinds a 1⁰ or 2⁰ per side primary bevel angle than an error of 1⁰ degree per side is fatal.

Jan

[Ken S]

Jan,
By using the Anglemaster with a substitute target, I believe we can match the error tolerance of the calculators. Maybe we should return to the simplicity of the Anglemaster until the calculator designers work the bugs out. I believe that day will come.
Ken

[jvh]

Hello,

good points from cbwx34 and Jan.

I agree that there is no practical difference on normal sharpening, if the consistency is kept.

It can be problem for some calculators because calculation error can vary with parameter changes, eg. different wheel diameter. It means that you will grind bevel angle with small error, eg. 20,3° instead 20° on wheel with dia 250 mm and than you will hone angle 19,9° instead 20° on honing wheel dia 215 mm, because of calculation error. You lose the consistency in this example, but there is no problem if you use honig wheel dia 250 mm, because error stays +0,3°.

Of course, question about "real life impact" caused with such error still remain...    In general, if you are satisfied / your customers are satisfied, use what suits you and what makes your job easier.

.. until the calculator designers work the bugs out. I believe that day will come.
Ken

It's already happened. 

[Hannsi1957]

The diffrent angles at using for example my software depends on the construction of the jig.
Knifes up to 3 mm thicknes are no problem. But if u have a thicker knife u have to modify ur clamp.
I am working on a idea to construct a clamp that closes from both sides similiar.
If i can find a way to do that all angleproblems done.
Cheers Hanns

[Ken S]

Jan,

The 1° error you mention, is it consistent? As an example, if what reads as 15° is actually 16° (or 14°), If the error is constant, we can either live with it or compensate for it. If that is the case, it doesn't seem any more of a problem than a mariner correcting his magnetic compass.

JVH,

If in the higher precision environment, variations in wheel diameter cause inaccuracies, the obvious solution seems to use consistent diameter diamond or CBN wheels.

Hanns,

I believe there is interest in your jig.

Ken

[Hannsi1957]

Hello, Ken,
I can well imagine.
It would mean the end of all jigs with 0.5 and 1 mm milled away material.
If anybody has an idea to realize this, he should tell me.
I think I am in a dead end at the moment.
We can then check the feasibility.
I am open for everything that could help me in the implementation.

cheers Hanns

[Jan]

Jan,
The 1° error you mention, is it consistent? As an example, if what reads as 15° is actually 16° (or 14°), If the error is constant, we can either live with it or compensate for it. If that is the case, it doesn't seem any more of a problem than a mariner correcting his magnetic compass.
Ken

Ken, John,

all programs discussed on this forum are okay except those that use the old, approximate Dutchman formula.

I think they are only one or two calculators that use the old Dutchman formula, which can cause an error in the Kenjig length up to 1 ¼ mm. This error is not constant but depends mainly on grinding angle and stone diameter.  One calculator which requires blade thickness behind the edge produces unacceptable jumps in the set up parameters.

If you are in doubts do not hesitate to contact me, jvh or cbwx for comparative calculation. The major calculators are mature now and use only Euclidian geometry to calculate the set up parameters.

Jan

[cbwx34]

Jan,
By using the Anglemaster with a substitute target, I believe we can match the error tolerance of the calculators. Maybe we should return to the simplicity of the Anglemaster until the calculator designers work the bugs out. I believe that day will come.
Ken

Fixed it.

Nice try.   

[RichColvin]

John,

From my research and readings I have come to believe that the exact angle only matters in two circumstances.

• Cutting tools used in metal work, especially lathe work.  Leo J. St. Clair did a lot of research and found that the angle change of 1 or 2 degrees made very real differences in the work required to perform the activity (Design and Use of Cutting Tools, 1952).
• Knives used by butchers.  Dr. Vadim Kraichuk also did a lot of research to show the best angle for knives used by butchers.  But these are professionals who get their knives sharpened on a regular period (weekly, I believe).

But, for things like wood turning, the angle matters less than the frequent resharpening of the tool.  And, I find the same is true with other items like my pocket knives.  Sharpen more and worry less about the angle.

As for my kitchen knives, well it probably matters more that my wife cuts on the stone countertops or plastic cutting boards than the angle of the blade.

But, this is just one man's opinion.

Kind regards,
Rich