Messages

Herman, the latter edge is after Japanese SJ.
The SJ definitely gives better result than going from a finely graded standard SG straight to the honing wheel.
I understand what you mean, and yes it is possible, but for the Japanese stone to hone out all SG scratches, I should have spent twice the time.
And the Japanese stone is most expensive, and soft and has to be declogged and trued frequently, wearing off quicker than any other stone.
So I limit knife processing on the SJ to acceptable minimum.

All my experience tells me that jump from finely graded standard SG stone to the 4000 grit SJ is way too much.
I have a dedicated SG stone which I grade only finely, and yet I wouldn't rate it at 1000 grit as the Handbook reads - I'd rate it at 600-800 grit.
And when you move the blade from that to the 4000 grit SJ, it's hard to level out all that bad scratches with this superfine stone.
Yet the Japanese stone definitely delivers more than the honing wheel, and for high end knives I cannot skip it.

I wish Tormek offered a dedicated waterstone of true 1000-1200 grit; using it after 220 grit, and then going from it to the 4000 SJ would be just perfect.

Thank you for your replies, guys.

Yes, this trial was all about handling Tormek standard setup with their knife jig.
In adapting my bench stone skills to recently acquired Tormek, I had to clear up the jig behavior for myself.

My past experience, and Steve's decades of sharpening, and everyone else's who sharpens freehand tells to keep the edge at the LOC.
However, when I clamped a Muela pig sticker into the jig, and sharpened at the LOC, the bevel I got was less than satisfactory; frankly, I ruined the knife tip.
It's in the first picture.
The pig sticker is 4.5mm thick at the heel.

I just had to resort to experimenting to sort this out, to save the pig sticker and my reputation.
The above trial helped me to understand that with thick & long knives taper comes into play, partly due to lever effect, and partly due to knife jig design discussed in http://forum.tormek.com/index.php?topic=2577.0

For these knives, pivoting the tip away from the LOC appeared to be the right technique when you use knife jig in Tormek standard setup.
It's the second picture, and I am happy with the result, and the Tormek.


Sharpened at LOC


Sharpened pivoting away from LOC

...

[RESULTS]

Hypothetical assumption voiced on this forum was that sharpening towards the tip should use a combination of lifting and forward pivoting to maintain the contact with the stone at the same line.
It seemed logical because the belly upward curvature positions the knife tip closer to the support as compared to the heel, and shorter distance to the support increases the grinding angle and narrows the bevel; pivoting forward was assumed to compensate for that.

Practical trials showed this assumption was wrong, moreover, thicker long knives with little belly curvature require pivoting the tip towards yourself/support, i.e. opposite to the hypothetical assumption.

I used 3 knives:
Thin & long knife - 19cm Global chef knife 1.8mm thick at the heel and tapered to 0.6mm at the tip.
Thick & short knife - 9cm Linder knife 4mm thick at the heel and tapered to 1mm at the tip.
Thick & long knife - 18cm custom camping knife 4mm thick at the heel and tapered to 1mm at the tip.




Knives were mounted in the jig as shown by Jan in
http://forum.tormek.com/index.php?topic=2562.15

This is a clever approach to avoid jig position effect on the bevel described in the Tormek Handbook p.53.

All knives were sharpened to included angle of 30 degrees by pulling across the stone WITHOUT pivoting, only lifting the handle of the knife as taper tells to maintain contact with the stone.
To help myself maintain the same blade position as the knife is pulled across the stone, I used Ken's idea of a laser to mark the initial line of contact, "LOC" in Elden's (kb0rvo) terms, as they discussed in http://forum.tormek.com/index.php?topic=2562.15

The same steps for all 3 knives:
- mark the bevel;
- set the 15 degree angle at the heel by manually rotating the wheel and checking the marking;
- sharpen from heel to the tip WITHOUT pivoting.







RESULTS

Thin & long chef knife - uniform bevel along the edge of 1.3mm.
Thick & short knife - uniform bevel along the edge of 2mm.
Thick & long camping knife - widening bevel, from 1.5mm at the heel to 1.8mm at the tip.







For these knives no pivoting was needed, even for the last knife the difference was practically negligible.

The only explanation I can think of is contrary effect of taper and upward curvature:
Because of the taper contact with the stone extends and bevel widens.
However, the belly upward curvature brings the tip towards the support, increasing the grinding angle and thus compensating for the taper.

Note that curvature of the thin & long chef, and thick & long camping knife used in the trial is comparable.
And note the bevel widening towards the tip of the thick long knife, though slightly (by 0.3mm).

Following the same logic, a thick and long knife with little upward curvature, sharpened without pivoting, will have even wider bevel to the tip. Sashimi knives and pig stickers are good examples of such knives.

And true, look at the bevel widening to the tip in the next picture, also sharpened without pivoting; now there is almost 1mm difference between the heel and the tip.


To produce a uniform bevel along the edge of this sashimi knife, I had to pivot the tip over 1 cm towards the support/myself.

CONCLUSION

Regular kitchen knives, as well as thicker but short knives do not require pivoting; lifting on the handle as taper tells is all you have to do.

Thick, long & narrow knives that are tapered towards the tip > 2mm, and have little upward curvature, require combination of lifting on the handle, and pivoting the tip towards yourself.
As a rough guide, you move the tip towards yourself about the same distance as the knife lifts over the edge of the stone, sort of translating the vertical movement into horizontal shift.

Knives with false edge require extra backward pivoting to increase grinding angle towards the tip (otherwise you'll grind it off).
With double edged knives and daggers, where you have to make two edges meet at the middle of the tip, as your grinding nears the tip, pivot the blade tip towards yourself , and stop grinding as the water flow reaches the very tip.

Wootz,
Please check if the edge is actually in the middle of the blade aslo!

Best ,
Stig

Sure, it factors as well.
Presuming the bevel mirrors as you turn over the knife jig was wrong for all the above reasons.
Now, with thicker knives, as I turn over the jig, I mark the bevel and use the jig adjustable stop to equal the grinding angle with the other side, normally the needed adjustment is within half a turn.

Thanks again, guys, for your hints.

Hi Jan,
Apologies for late reply, I was out bushwalking over weekend.

The M12 bolts allow some degree of horizontal freedom, ie I move the attachment back and forth; while the universal support offers vertical adjustment by design - these together fit cleavers of various shapes.
For honing knives I move it to the case.
For sharpening a wider cleaver I sometimes insert the attachment upside down as to what is in the pictures, to distance it from the stone.

With BGM-100 I could do without those bolts and wood, but was reluctant to drill the front of the Tormek as it is still under warranty.

If you happen to have a sisal buffing wheel with white or black emery compound, the below method shown on youtube works wonders.
The only thing I do differently to the video, is that I sisal-buffer only the serrated side, and then hone the flat side.
After sisal buffing the serrated side, on the flat side you can feel, and sometimes see an irregular microburr that you gently hone away.
Takes 2 minutes per knife all together.

https://www.youtube.com/watch?v=iaa0_ASuYGE

[Frontal Vertical Base]

2018 Update: We have started manufacturing a Frontal Vertical Base for honing and grinding away from the wheel - please check our website knifeGrinders.com.au
And below is the story of how it all started in 2016...

Being so grateful to this forum for heaps of helpful hints, I just want to pay back sharing my honing attachment.
I gave up on freehand stropping long ago, because no matter what technique I tried, I dulled the edge. I admit it is entirely operator error, but alas not everyone is born with freehand talent.

Thanks to two M12 x 120mm bolts, a piece of 35mm wood, and parts from the BGM-100 kit, I can now strop under a set angle.
4-6 slow passes across the wheel on alternate sides of the blade with very light pressure delivers hair splitting edge.
Pictures are self-explanatory.









Flipped to the right, accommodates cleavers thanks to farther distance to the stone compared to the standard support.

Color the bevel with a marking pen before testing your 18 degree bevel. See if the bevel angle needs adjusting.

Your knife is stonewashed, isn't it?
You have to protect blades with coating, blackened etc with strips of dense tape, or the zinc jaws of the knife jig will scratch it. Eg I  use medical tape (Elastoplast), just mind that a regular electrical insulating tape will not do, it scratches through it.

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

[kb0rvo]

kb0rvo, your post is my gut feeling explained in plain and precise terms.
With the next hunting knife I'll definitely try marking position of the clamp on the blade, and turning over the blade in the jig rather than the jig itself. And if it delivers better result, for collectible knives I can put up with the inconvenience.

Such a clever and responsive forum, pure pleasure to look in.

I found out that... the stone was out of true. 
The stone was slightly conical, causing the change in angle on flipping over the blade.
Truing the stone has eliminated that.

Thank you, Ken

Recently started using the Long Knife Jig SVM-140, and noticed that bevel on one side gets always wider than on the other.
Trying to understand what's happening, having turned it over to the second side checked the angle again with the AngleMaster, and was surprised to see the angle is not the same.
The problem is with both kitchen knives and thicker hunting ones.
Now to obtain the same bevel on both sides, I have to adjust the angle every time I flip over the jig.

The only explanation I have is the way they manufacture the jig does not center the clamp right.
Have never had this issue with the regular Knife Jig SVM-45.

Has anyone had similar problem? My jig is of newer design (without locking screw on the stop).
Am thinking of grinding inner surface of one of the clamps to compensate for the asymmetry, but decided to check with you guys first.