revisiting the kenjig

[Ken S]

 I designed the kenjig shortly after Dutchman
(Ton Nillesen) posted his Simple and Accurate Grinding Angle Adjustment booklets on this forum in 2013. Dutchman's tables were and still are the foundation for the kenjig, as well as for later computer angle setting programs.

I differed slightly in my choice of tools. Dutchman used a combination square. Later programs generally use digital calipers. In my opinion, the constraint both in time and accuracy with these tools is the need for ongoing measuring. The kenjig is designed like a gage block. In the world of precision measuring, tools like rules, calipers, and micrometers generally have an accuracy tolerance range limited to thousandths or ten thousandths of an inch. While this is more than adequate for sharpening purposes, hardened steel gage blocks can be made to accuracy within a few millionths of an inch for laboratory work. They also do not require remeasuring as do other measurement tools.

The kenjig is designed to allow the user to return to the shop several months later and reset the machine and jig exactly without any need of measuring. ( I am not ignoring the inevitable slow decrease in wheel diameter. I have dealt with that previously and will readdress it.)

The foundation of the kenjig has not changed. However, several factors have emerged necessitating the need to adapt. The most notable is the recent switch to more acute grinding angles. This was noted in Dutchman's original booklets and more highly researched by Vadim Kriachuk (Wootz). I remember reading about this in Dutchman's booklets, however, until recently I have been too influenced by conventional practice. Initially, I made kenjigs for both 15° and 20° (degrees per side or half of the included angle). From the start, I realized that I was only using 15°. The knives I sharpen are better grade stainless, typified by Victorinox. Through Wootz' research, I now realize that 12° will produce better results, and am "retooling" to 12°.

I realize that higher end sharpening is increasingly involving using multiple grinding wheels. I see no problem using multiple kenjigs for different diameter grinding wheels or angles when needed. These should be clearly labelled.

From the start, I wanted to use common Projections and Distances for all  standard knives. This feature was designed for the farmers market sharpener who had to frequently switch between chef's knives, slicing knives, and paring knives. I solved this by using three different jigs, each set for a typical knife in its range. This meant only minimal tweaking and frequently no tweaking between knives. I used a SVM-140 for chef's knives; a discontinued SVM-100 for slicing knives; and a combination of the SVM-45 with an SVM-00 to provide the common Projection of 139mm.

I never liked having to use the combination for paring knives. The SVM-00 is primarily designed for carving knives with large wooden handles and small blades. I found it usable but clumsy for paring knives.

Gradually I became aware that the real reason for separating the knife groups was because of the width of the knives, not the style. I also became aware that my chosen 139mm Projection (as well as the 140mm Projection favored by Wootz) was dictated by the relatively short thread length of the current knife jigs. I was all ready to take my SVM-45 to my local machine shop and have it fitted with a custom machined shaft with longer threads when the pandemic shelter in place order happened in Ohio.

During this enforced time at home, I observed that the thread length of my older SVM-100 was considerably longer than either my SVM-45 or SVM-140. I emailed support, who advised me that until 2002, both jigs had longer thread length. Tormek redesigned the jigs because of problems caused by some users incorrectly leaning on the longer shafts.

I needed a pre 2002 SVM-45. After initial failures, I eventually purchased two of them. With the older, long discontinued design, reaching 139mm Projection with narrow paring knives is no problem without needing the SVM-00. A major hurdle has been overcome.

The original design of the kenjig is still sound. The user may choose his desired grinding angle or angles. A separate kenjig will be required for each angle. As these are easily made in a home shop at quite minimal expense, I do not see this as a problem. To compensate for changing grinding wheel diameters, one can either dedicate a kenjig to the particular grinding wheel and increase the Distance groove length by about a millimeter for each five millimeters of wheel diameter loss or make up a set of kenjigs with different groove length. For essentially "one off" work, like sharpening my Chinese cleaver, a simple cardboard kenjig is quite adequate. I also recommend starting with cardboard jigs to see if someone likes the idea.

In spite of the benefit of using the pre 2002 jigs, I realize this is not practical for most users. I need to update and rewrite the pdf I made several years. Experienced users can certainly adapt today's conditions to the older pdf. This might be more difficult for newer users. I will rewrite the pdf.

I have always perceived the kenjig as peacefully coexisting with the computer programs. Each has its place and they complement each other. A program is far superior to trial and error for initial set up. Once the initial set up is established, a kenjig is much faster and just as accurate for repetition, especially for wheels which do not change in diameter.

Ken

[John_B]

Have you developed jigs for honing as well?

For my knives I have been using 1.5°-2.0° greater angle for honing with very good results.

[cbwx34]

...
I have always perceived the kenjig as peacefully coexisting with the computer programs. Each has its place and they complement each other.
...

Here you go... the video... now at 12°... to complement the new KenJig!


https://vimeo.com/446212489
(Sorry, no music!)

[Ken S]

Good question, John. There are four variables involved. You have to set the diameter of the wheel. For honing, whether with the leather honing wheel, felt, or paper wheels, the diameter will remain constant, as it does with diamond and CBN wheels. Once inserted into the equation, there is no reason to change it. (If you use multiple wheels for honing, you will need one equation for each diameter or honing angle.) If you sharpen at 12° and hone at 13.5° (or whatever setting you choose), you will need a separate equation for grinding and honing. In my opinion, the easiest way to do this is to make separate color coded and labelled kenjigs. You will find that making several kenjigs requires very little more time than making one. Use the same tables or calculator you used for the first kenjig to make up the others. In actual field use, this is less complicated and faster than it seems reading about it.

CB, I like your new calculators. I would use them by printing them out. I would put the "future calculators" (for worn diameter) in an envelope and keeping the current calculators on top of the envelope somewhere near the Tormek.
This process, in my opinion, allows for the optimum use of both the calculators and the kenjig. The initial set up of the kenjig is done with the calculator, utilizing its versatility and mathematical precision. Once this is completed, the process switches to the kenjig for day to day efficiency. This gives us the best of both worlds.

Ken

[cbwx34]

...
The kenjig is designed like a gage block.
...

I actually have a KenJig question...

Are you still measuring from the top of the USB, or now the bottom?  I interpret "gage block" as being set between the USB (bottom) and the wheel... but in your old description, you show it top of the USB to wheel...



... (or maybe I don't know how exactly a gage block is used?)... 

[Ken S]

CB,
I use it as shown in the photo, from the top of the support bar to the grinding wheels. I used the underside of the support bar on one of the early prototypes. It was wedge shaped. I soon switched to the present shape; it seems simpler.

"Gage block" may not be the technically correct term. I use it to indicate an accurately made block with no measurement calibrations. Among other uses, gage blocks are used to check the accuracy of micrometers.

Ken

[cbwx34]

CB,
I use it as shown in the photo, from the top of the support bar to the grinding wheels. I used the underside of the support bar on one of the early prototypes. It was wedge shaped. I soon switched to the present shape; it seems simpler.

"Gage block" may not be the technically correct term. I use it to indicate an accurately made block with no measurement calibrations. Among other uses, gage blocks are used to check the accuracy of micrometers.

Ken

Ok... I don't know... I looked them up and all I could find was it used in between two points... but someone could probably say for sure.

Thought I was gonna have to redo the calculator! 

...

CB, I like your new calculators. I would use them by printing them out.
...

This might be easier to print... 

[Ken S]

Agreed. If you can add the 139mm Projection, we would have the whole shot!
Ken

[cbwx34]

Agreed. If you can add the 139mm Projection, we would have the whole shot!
Ken

[Ken S]

Perfect. Thanks, CB. I will print it.
Ken

[cbwx34]

Looking for another post, I ran across Jan's "Chart for kenjig diemensions" thread...



...which made me consider the question... have you done any actual testing to see if it's worth it to reconfigure everything for a 3° difference?  There are reasons not to... for example edge durability.

You might consider doing some of your own testing before making this decision.... just a thought.  A lot has been documented based on the current setup.

[Ken S]

CB,

Just out of curiosity, do you have a preferred grinding angle?

Ken

[cbwx34]

CB,

Just out of curiosity, do you have a preferred grinding angle?

Ken

Usually... 15°.   

[Ken S]

CB,

I have long been fascinated with understanding why people have the preferences they do. For most of the decades I spent working in my amateur photo darkroom, I used one film developer, Kodak HC-110. Like thousands of photographers, my choice was influenced by Ansel Adams. HC-110 was Ansel's preferred film developer for all size negatives, from 35mm to 8x10". It was an excellent developer, versatile and consistent.
I'm sure film chemists could point to many technical charts favoring it. I always wondered why Ansel preferred it for all negative sizes. The imp in me thought he may have liked having to store only one long lasting bottle of film developer, a definite convenience. Not that it would have been an influence, however, as a consultant for Eastman Kodak, I doubt he ever had to pay for it. I do not mean to cast aspersions. HC-110 is an excellent product and Ansel was an outstanding person and photographer.

Back to sharpening. Why 15° (degrees per side)? When I started using the Tormek, the conventional wisdom in the US was 20 degrees per side. Then, as now, people liked simplicity, one size fits all. In his knife sharpening video, Jeff Farris used 20°. in the US, it was traditional. Gradually, 15°, "the European standard", started making inroads. More recently, Vadim has published his research recommending 12°.

Just like with Ansel, I wonder why Vadim prefers 12°. I think a main factor may be the knives he sharpens. I am certain that he has sharpened all kinds of knives from super steel to not so super steel. However, a large part of his business is knife rental to the meat industry in in Sydney. His preferred rental knives are made by Victorinox. These knives can hold an edge at 12°. He might prefer 15° if half of the knives he shapened were inexpensive grocery store knives.

As I generally only sharpen my own knives, mostly Henckels and Victorinox, I would feel comfortable standardizing at12°. If I sharpened for other people, 15° would seem safer.

Ken

[cbwx34]

...
Back to sharpening. Why 15° (degrees per side)? When I started using the Tormek, the conventional wisdom in the US was 20 degrees per side. Then, as now, people liked simplicity, one size fits all. In his knife sharpening video, Jeff Farris used 20°. in the US, it was traditional. Gradually, 15°, "the European standard", started making inroads. More recently, Vadim has published his research recommending 12°.
...

Yes 15dps.  Like many, I started higher based on recommendations, over time I settled on 15dps probably for a number of reasons... but mainly it does what I want.  Not all knives get it especially knives I sharpen for others... for example, if I receive a knife that obviously gets a lot of abuse I'll go higher.

But my point was to suggest you test for yourself, and not base "retooling" on someone else's suggestion or study.  15dps has obviously served you (and others, for example see the link to the graph Jan made) well... just seems to me it would be worth it to test a few blades before redoing everything (especially if you can do a bit of a blind study).  For example, you wrote... "Through Wootz' research, I now realize that 12° will produce better results, and am "retooling" to 12°."... without ever suggesting that you sharpened a knife or two to 12°, to see for yourself.  (You stated earlier you did test between 15° and 20°, for example).

I think too, that if someone is using the Kenjig to sharpen... picking an angle that is more "neutral" makes more sense than picking one that might be more subject to failing, harder to reprofile to, etc., and will perform better in a variety of circumstances and conditions.

Edit:  In fact, see jvh's posted which to me is related...

https://forum.tormek.com/index.php?topic=4425.msg31499#msg31499