Sharpening for a better burr

[Ken S]

Herman,

With this kind of jig, you don't need angle adjustment. The angle is adjusted by the position of the jig. The jig is designed to keep the knife flat. Steve explains in his book and DVD how to set the angle. Placing the blade flat at the top would be a zero degree angle. A quarter of the circumference would be a ninety degree angle. Splitting the ninety would be a forty five degree angle. Drawing two lines, one top dead center, and the other an inch and a half away is approximately eighteen degrees. Think of the wheel as a protractor.

The advantage of this system is that the knife is always help flat.

Ken

[Elden]

In the image below you can see how it was assembled. I used massive steel square, drilled two holes for M12 (1/2")  bolts, which anchored this support into the vertical sleeves. I added one low nut as a micro adjust.  Then I bolted small steel plate to the longer arm of the steel square. This plate can serve as horizontal tool rest.



The whole jig can be flipped over to enable grinding away from the edge. 

Jan

Herman, his first photo shows his micro adjust nut more clearly than the most recent photos.

[Jan]

Yes Herman, I know from your previous posts, that you prefer grinding towards the edge. 

When I wrote that comment, Jan, it was in response to the wooden platforms I saw on a previous page. I hadn't seen the photos you had posted of your platform. It's well built, and a work of superb craftsmanship and inventiveness. I don't see, though, how you adjust the angle. It seems you could fashion a micro adjuster quite easily as you already have threaded bolts inserted in the universal support sockets.

OK, Herman, that clarifies your comment.
Thank you for your kind words concerning my platform prototype. I appreciate it. 

As already explained by Ken and Elden the flat platform height defines the bevel angle.

The simplest way is to mark the desired bevel angle on the side of the grindstone. Then you rotate the grindstone so, that one mark becomes the dead top center. The other mark defines the position where the flat knife rest edge (strictly speaking the knife edge) has to meet the stone.

The other method is based on measuring the circumference of the whole grindstone and calculating which part of it corresponds to the desired bevel angle. E.g.: for the grindstone circumference of 30" and the desired bevel angle of 18 degrees we get 1.5" arc length measured along the grindstone's edge (1.5" = 30" * 18deg / 360deg ).

I have crosschecked the accuracy of the 18 degrees bevel angle adjustment with the Tormek Angle Master. The result was satisfying, my reading of the WM-200 was 19 degrees.

Jan

P.S.: Herman, the above described bevel angle adjustment technique is not restricted to flat = horizontal platform configuration. It will work well with your steeply inclined knife rest, also!

Guys, I am sorry I do not have Steve's book or DVD, so I described how I adjusted the flat platform based on my knowledge of Euclidean geometry. I hope my considerations are not biased. Conducted cross-examination calms me down. 

[Jan]

In the sketch below you can see geometrical reasoning for the above described method for the (flat) platform adjustment. The height of the knife edge above the center of the grindstone defines the bevel angle beta.



Jan

P.S.:
The secant (shown in blue) corresponding to the central angle 2*beta has also large potential for angle/platform adjustment. 

For simplicity, I've modified an image from the booklet by Ton Nillesen, where the blade is in the Tormek knife jig. The same applies when we are grinding freehand using the (flat) platform support.

[SharpOp]

Excellent work, folks!   When I saw Herman's question/comment about adjusting the platform angle, I thought "must draw or find others' drawings to explain."  Then I discovered that Ken and Jan (and maybe Steve in the sharpening school video) have already done all the 'splainin' required.

Herman, this approach to measuring and setting the bevel angle, based upon a blade held "level" (cross-section midlines parallel with the base plane of the grinder), is the one I've always found easiest to internalize.  Once I really got it, I realized that I could actually grind acceptable primary bevels freehand on many kitchen knives.

I had to refresh my memory of high school geometry and trigonometry (my math(s) is/are not as fresh as Jan's) to make sure I actually understood the procedure, but it feels at least as natural and intuitive as the AngleMaster.  ;^) 

  ~Doug

[stevebot]

Thank you Jan for the fine illustration of edge angle.  Of course the same applies for freehand sharpening. Just hold the blade level X degrees from the top of the wheel and sharpen away.

[Jan]

You are welcome, Steve! 

I would like to ask you, why is longer exit burr better than a shorter one, when we afterwards remove the burr on the honing wheel anyway?

Jan

[stevebot]

Larger means we detect it sooner, wasting less of the knife, assuming we check often during the sharpening process.

[wootz]

Reading Dutchman's tables, his thoroughness reminded me of the "Experiments on Knife Sharpening" by John D. Verhoeven
http://www.mrsoso.nl/bushcraft/knifeshexps.pdf

In his chapter "Experiments with the Tormek machine", honing on the chrome oxide loaded leather wheel produces 0.35 microns edge as shown by scanning electron microscope.
The human hair cuticle is about the same thick, and a blade that sharp whittles a human hair lengthwise.

For that sharpness, honing must be done under controlled blade angle, however, no prefabricated jig exists for honing knives on Tormek.  The Tormek universal support in horizontal position at the honing wheel has restricted working range, albeit enough for chisels, but not for longer blades like knives.
If you need a honing jig for knives, you have no choice but to make it yourself, and looking at Jan's last version of horizontal support, I see it as a prototype support for honing.

Just wonder if this approach is capable of bringing knife sharpness to this level?  - Diamaze-PSD-razor-blade-slicing-a-human-hair
https://www.youtube.com/watch?v=PNq4Oa1GwwE

[Jan]

Larger means we detect it sooner, wasting less of the knife, assuming we check often during the sharpening process.

Thank you for the quick response, Steve! Now it gives me a good sense. 

Jan

[Jan]

For that sharpness, honing must be done under controlled blade angle, however, no prefabricated jig exists for honing knives on Tormek.  The Tormek universal support in horizontal position at the honing wheel has restricted working range, albeit enough for chisels, but not for longer blades like knives.
If you need a honing jig for knives, you have no choice but to make it yourself, and looking at Jan's last version of horizontal support, I see it as a prototype support for honing.

Point well taken, Vadim! 

My design, of the height-adjustable flat platform, will work well with the honing wheel, also. Just double flip the main framing square mount.

Far more practical would be to extend my main framing square mount by another arm parallel with the side of the honing wheel. So we would get a new, U-shaped square mount. This would allow grinding and honing, away from the edge, without any complicated platform adjustment.

Jan

[Stickan]

I find this post interesting and have followed it and I will add to this post that using the honing wheel freehand is easier than to sharpen freehand on the stone. The leather is very forgiving and gives a great edge, as long as you don't lift the blade to much and get a to steep angle so you round the edge.

With a platform you will/might bump into the stone with the tip or handle on chef's knives. Jan has an interesting idea about the U-form though.
Remember that the stone gets smaller during the years and the leather wheel stays the same.

When honing with the same ideas that are in this post, but freehand, and with a movement so you don't bump into the stone, the edge will get razor sharp.

Sharpening with the stones direction will give a longer burr and it takes longer time to hone but it's easier to feel with the fingertips.
Sharpening towards the stones direction has a bonus that you use the water to see that you are holding the knife flat on the stone and the stone don't get uneven as fast, and you don't need to true it very often. It is also a bit faster but needs some more practise and caution so the knife don't catches edge of the stone.

Best,
Stig

[Jan]

Thank you for you statement, Stig. 
Your highly relevant point is very well taken!

Your views are especially important for the thoughts, concerning the emerging  U-shaped framing mount for sharpening and honing, away from the edge, without complicated flat platform adjustment.

Jan

[Ken S]

Good thoughts, Jan and Stig.

Steve,

Several posts have raised concern about the knife lifting while being sharpened with the wheel moving away from the knife. Should you please comment on this?

Thanks,

Ken

[Herman Trivilino]

The secant (shown in blue) corresponding to the central angle 2*beta has also large potential for angle/platform adjustment. 

Note that the blue line need not be a level line. It is in this case because the platform is level. But all of the geometry works the same if the platform is not level. One way of understanding this is to imagine rotating the entire apparatus until the blue line (platform) is level. When you do that the bevel angle remains unchanged.