Grinding software upgrade is coming

[Morne1312]

Where can one get more info regarding the Kenjig or how it works (set up, working etc?)

[Jan]

The original description of kenjig concept's you can find e.g. here:
http://sharpeninghandbook.info/Images/Tool-Jig-KenJig.pdf

About my modification to double-ended kenjig you can read e.g. here:
https://forum.tormek.com/index.php?topic=2654.0

Jan

[Ken S]

Morne,

Be sure to pay close attention to the very informative photo Jan has included showing his double ended jig (what I call the "Janjig").  Jan's jig incorporates the very useful function of determining the Distance to the leather honing wheel (220 mm diameter). Jan has wisely decided to limit his jig to one bevel angle (15°). Having the jig for only one angle lessens the possibility of error. For angles other than 15°, the Protraction can be kept at 139 mm. Only a separate Janjig would be necessary. I would paint the second Janjig a different color to keep things simple.

The kenjig concept is designed to be "one size fits most" rather than "one size fits all". I designed it for three groups:
1) New users to simplify knife set up.
2) Infrequent users who need a simple set up with fewer skills to remember.
3) Farmers market sharpeners who need a very time efficient set up procedure to sharpen many knives quickly.

The applet and other programs are clearly preferred for high end sharpening, where the customer's original bevel or desired angle must be matched. In these cases, time involved is not as critical. My knife sharpening is my home knives. I standardized at 15°, although, following the new research, I am leaning toward converting to 12°. That will mean a few minutes and a bit more material to make up a new kenjig and a Janjig. I also keep the applet "at the ready" for higher tech work.

Ken

[John_B]

Ken, have you also made allowances on your jig for setting an alternative honing angle on knives as detailed in Wootz's book on deburring?

[Ken S]

Good question, John.

No, the kenjig predates Wootz' deburring book. You make a good point; I should update the kenjig. I would leave the Projection at 139mm and make special kenjigs (or Janjigs) for the Distances for the deburring stages.

Keep on thinking.

Ken

[cbwx34]

NEED FOR UPGRADE
In its current form, our software sets an accurate grinding angle for resharpening a knife with established bevels at the existing edge angle.
E.g. you resharpen a 15 degrees per side (dps) knife to the same 15 dps.

However, when grinding new bevels, sharpening a grossly dull knife or a knife blank gives an edge angle differing from the calculated target by 0.5-1.5 degree. The thicker is the blade behind the edge, and the lower is the new edge angle, the greater is the difference.
....

STATUS
I've coded the computer algorithm and currently testing in sharpening blades of varying thickness.
The calculations are along the lines of the explanation given by Ton Nillesen in 2018 on the page 6 of his additional booklet that can be downloaded from our website http://knifegrinders.com.au/Manuals/Grinding_Angle_Adjustment_Booklet_2018.pdf
....

After wootz posted this topic, I took another look at the section in Ton's (Dutchman) book on thickness...



... and quite frankly, I don't understand it.  (So, by default, I'm not saying wootz is right or wrong... I need clarification of the section).

Ton states that if you start grinding a thick blade, you're measuring to "Kb", but as you grind you end up out to "Ke".  This, to me, is not the case.  If I put a knife or wood like he did, in a clamp,...



and measure the projection distance, I am measuring the total projection distance (Ke).  I'm never measuring to "Kb".  So, the calculator/formula automatically is set for the angle I want to end up at.  While it is obvious that at the start of the grind, the angle of the knife/wood in relation to the stone is different, at the end, I'm getting the angle the calculator provided.  That's the way I see it anyway.  (I actually did it to see if I was missing something).

Another part that has been left out of this conversation is the quote on p. 7....  "Furthermore this error is not present or negligible with sharpened blades".  Wootz even states above that his previous version "sets an accurate grinding angle for resharpening a knife with established bevels at the existing edge angle."  So, if I put in a thick blade, and wanted to set a new bevel, and use the new formula adjusting for thickness, I end up with a different USB height, than if I had the same blade and just wanted to sharpen at the current angle.  Isn't that a contradiction?

The only way you'd see a difference, is, (as someone else said), you start with a blade sharpened at a lower angle, that you want to put a higher angle bevel on.  This would grind right at the edge, and reduce the projection distance.  But, from what I can tell, the formula Ton provides, does not address this.  You could take off as little or as much metal you want, since each pass is right at the edge of the bevel.

In reading the section before, on "Comparison with the "Anglemaster", I'm led to believe that the "thickness error" is relative to the section on adjusting for thickness... i.e. if you want to compare the formula with the Anglemaster, you need to account for the thickness of whatever you're measuring.  (But that is my guess).

My opinion, based on my testing, is that the updated formula Ton provides on p.10, produces the desired angle at the end, with no need to adjust for thickness.  I don't understand what Ton's formula regarding thickness accomplishes.  SO, if I'm missing something, in this or in Ton's section, feel free to tell me. What exactly is Ton describing here? 

[cbwx34]

Where can one get more info regarding the Kenjig or how it works (set up, working etc?)

Ken, have you also made allowances on your jig for setting an alternative honing angle on knives as detailed in Wootz's book on deburring?

Good question, John.

No, the kenjig predates Wootz' deburring book. You make a good point; I should update the kenjig. I would leave the Projection at 139mm and make special kenjigs (or Janjigs) for the Distances for the deburring stages.

Keep on thinking.

Ken

Well, since I'm here....

You don't need to make a Kenjig.  Get a caliper with a lock...



... or any measuring device similar to this...



... and you have "Kenjig", that you can "lock" to a particular distance, but also adjust as needed when things change. 

[John_B]

I actually have not made a jig but use calipers for my measurements. I do try and use a standard distance between the knife jig and blade edge.

[Ken S]

The real secret of kenjig theory is standardization, not the tool itself. Of course, calipers and combination squares are adjustable, however, one can make a lifetime supply of kenjigs for a fraction of the cost of either adjustable tool. Also, the reading of a kenjig remains constant, with no need for constant remeasuring.

Ken

[jvh]

... and measure the projection distance, I am measuring the total projection distance (Ke).  I'm never measuring to "Kb".  So, the calculator/formula automatically is set for the angle I want to end up at.  While it is obvious that at the start of the grind, the angle of the knife/wood in relation to the stone is different, at the end, I'm getting the angle the calculator provided.  That's the way I see it anyway.  (I actually did it to see if I was missing something).

I explained this partially in my previous post (Reply #33 on: November 04, 2019, 07:24:36 pm).

We can say that that total projection distance X is always right. The dimension starts at the edge tip and this is also the first point of our axis.

If you have symmetrical double bevel knife and you center it well in the jig SVM-45 then the second point of axis lays in the axis of the jig and goes through point J.

Now it depends on used math because you can suppress this "thickness error" from the beginning with the correct calculation.

TormekCalc calculations are made in the axis of the knife (point at edge tip) and the jig (point J), so results are valid for all symmetrical double bevel knives with defined angle at the edge tip. Error given by material thickness is suppressed there completely.

For single bevel knives or non-symmetric bevel knives is a correction necessary to get the "right" axis.

1. You can put some distance pad to the jig clamp to get "virtual symmetrical" edge - then the edge tip will shift to the axis of the jig.
2. In TormekCalc you can change diameter of USB or jig diameter value and "virtually" move the jig axis to the right place by change the JC dimension. Then you get exact results for single bevel or non-symmetric knives. Error given by material thickness is suppressed by the jig axis shift.
3. You can change USB height too but there isn't exact calculation for this at the moment.

jvh

[Dutchman]

...
I don't understand what Ton's formula regarding thickness accomplishes.  SO, if I'm missing something, in this or in Ton's section, feel free to tell me. What exactly is Ton describing here? 

At your service 
I have corrected text, Figure 6 and the table in "More math for the Tormek grinder" in the paragraph "Understanding why thickness matters"
The documents (See link in my signature) have been updated.

[cbwx34]

We can say that that total projection distance X is always right. The dimension starts at the edge tip and this is also the first point of our axis.

If you have symmetrical double bevel knife and you center it well in the jig SVM-45 then the second point of axis lays in the axis of the jig and goes through point J.

Now it depends on used math because you can suppress this "thickness error" from the beginning with the correct calculation.

TormekCalc calculations are made in the axis of the knife (point at edge tip) and the jig (point J), so results are valid for all symmetrical double bevel knives with defined angle at the edge tip. Error given by material thickness is suppressed there completely.
.....

jvh

Thanks for the reply.  I agree with this.

At your service 
I have corrected text, Figure 6 and the table in "More math for the Tormek grinder" in the paragraph "Understanding why thickness matters"
The documents (See link in my signature) have been updated.

Thanks for the reply and "corrected text".  I do have one more question though.  On the next page, you make the statement..

It will be clear that these considerations are related to single sided grinding. For double sided grinding the values Ke and tb will increase with 50% for grinding the first edge. Furthermore this error is not present or negligible with sharpened blades

In my view, this should say something like... For double sided grinding the values Ke and tb will increase with 50% for grinding the first edge, if you grind to the opposite side of the blade on the first edge.[/b] (Or something to that effect).

In other words, if I have a blunt blade, and grind one side to a burr, then flip it over and do the same, there will be a bit of an error (and also a reduced Projection Distance).  But, if I have a blunt blade, and grind each side a bit at a time, until I reach the center, then there is a negligible error.  (I know this is an ideal condition, and some of this is just wording, but I think it might clear up some of the issue).

...................................
Which perhaps comes back to what wootz is trying to do/say/correct for... if you have a blunt blade, and grind one side to a burr, then flip and repeat, there will be a bit of an error or difference, that needs to be adjusted for.  My questions to wootz would be, did you also update the formula (which I think is more accurate, regardless of thickness).  I would also ask, why, once a blade is sharpened, does your calculator still require a thickness entry, if the error/difference is no longer there?

I think we're all on the same page, or close anyway... it may just depend on how the blunt blade is actually ground?

[smurfs]

Dutchman, please would you confirm if I am correct in thinking that the objective of the formula adjustment is to shift the tangent from the bevel edge to the blade center line so that the target angle occurs at the mid-point of the hollow grind, not at the edge?

If so (and if I'm not mistaken) the tangent at the blade mid-point runs parallel to the chord so I guess what your formula is effectively doing is calculating the angle of the chord, not the edge angle. Could this be the source of much of the confusion evident in this thread, or am I muddying the waters further?

[Dutchman]

...
calculating the angle of the chord, not the edge angle. Could this be the source of much of the confusion evident in this thread, or am I muddying the waters further?

You are right AND "muddying the waters further"

[smurfs]

...
calculating the angle of the chord, not the edge angle. Could this be the source of much of the confusion evident in this thread, or am I muddying the waters further?

You are right AND "muddying the waters further"

Or may be not...
So the enhancements that wootz has made to his software is in effect calculating the chord angle using the target grind angle, which means the angle at the edge is more acute. That being the case the finer edge angle goes some way to explaining how wootz is achieving lower BESS scores with the software tweaks, improvements I might add are probably at the expense of edge retention.
...more muddy water?