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Hey guys,

I was curious how many regular knife sharpeners felt like they had to buy the US-430. So here goes, thanks !

Ken,

Two additional jigs might be an additional expense, but at least people would get to choose. And out of curiosity, can you find receipts or emails so we can compare how much cheaper the SVM-45 were compared to the SVM-100 when the shaft was shortened ?

As for modifying a KJ, I don't feel like machining plastic, and I fear the risks (like not ending up with a smooth shaft) make it not worth the trouble.

Wrt the US-430 I respectfully disagree with the statement that

This jig is useful only to knife sharpeners who sharpeners who work with longer knives, a small part of the Tormek users

as it allows for much more leeway in terms of clamping position. So it is also very useful for knives with a pronounced curvature, or when wanting to adjust for the sweetest lifting/pivoting movement.
I'd be curious to know how many readers of the "knife sharpening" forum don't own the US-430. Keeping in mind that the Knife forum represents about 70% of all posts among the specialty forums, and more than six times the number of posts of the wood turning forum, I think this is a significant part of the Tormek user base.

I could not agree more with the need for an adjustable stop. The self centering feature is good... for about one knife out of the 20+ I use on a regular basis.

I'd trade the bottom stop any time for the adjustability (the adjustability range can easily be made so that it would allow sharpening weeding sickles, as well as much narrower blades). I use the SVMs much more than the KJ, but more often than not, the bottom stop catches when I switch sides, and I passionately hate that. Sure, it would probably go away if I used it more, but it's a PITA to me still.

The way I do things now with the KS-123 : I set my knives up in the jigs the way I did  before, so they all have the same protrusion distance, then I set up my VUSB and FUSB with the KS-123, and off I go.

I never added oil except as per the instructions when the honing wheel was brand new. It is now pitch black, completely smooth and I never scrape it.

When sharpening the first knife of a new session, I only add a bit of compound, by applying the tip of the tube and barely squeezing while moving the tube sideways. It leaves a tiny bit of paste wrapped twice or three times around the wheel.

I then hone for two to thre passes, then (yuck) remove whatever paste is left on the blade with a finger and rub it back onto the wheel. Makes for a dirty fingertip, but the wheel always feels the same.

In my experience, there is also some kind of a visual cue, with tiny black debris that start lifting off the wheel when deburring is efficient.

Or ... use a calculator 

John, those drums are beautiful. You must be very proud.

Having said all this ... I am not sure if you ever file a warranty claim, they would have an easy way to know that you have used a wheel on an extension shaft.

All Tormek wheels are either exclusively for wet grinding (SB/SG/SJ), or wet grinding is very strongly advised (DC/DF/DE).

There is only a water trough on one side of the machine, so the other one would have to run dry with standard issue Tormek hardware.

Therefore I don't see how they would support using it in a way that would only help 3rd parties sell wheels.

I think if I ever need to sharpen a ceramic knife, I will stick with the DF wheel.

Ken, based on the findings of the scienceofsharp article, the finer the grit the better, so you should probably go for the DE wheel.

But from there I think it would best to move on to higher grits.  I wonder if the Japanese Wheel would improve the SG result?

My .02: you'll shape the wheel long before you notice any significant difference in the finish of the ceramic blade.

As explained in the scienceofsharp article, you need a hard support with fine particles to sub-microchip the edge in a consistent fashion.

Your edges look nice.

I was just commenting on this sentence :

Scratches in a ceramic knife apex work as crack initiators, and when those scratches get smaller and smaller due to progressively finer polishing the apex becomes more resistant to chipping as well as keener.

If anything having "smaller scratches" will increase the mechanical constraint due to local traction forces, so if this was the driving mechanism, the edge would be more prone to chipping.

But I think what's at play here is that higher RMS roughness along the edge results in areas where there is little material left at the apex, and these fragile areas will break off easily.

Back to the post of the OP, the SG is indeed much too coarse for it being any good on ceramic knives : it will tear off huge chips due not to the hardness of aluminium oxide, but to lateral stress on the blade at a scale corresponding to the rougness of the stone itself.

As a general comment, if you polish a scratch, you're essentially flattening the ridges, but the bottom of the scratch remains as it is. So there shouldn't be an impact on fissuration mechanisms.

That being said, I don't think these mesoscopic cavities are what drives the chippiness. As mentioned in the article :

the blade consistently separates along grain boundaries resulting in sub-micron roughness

.

The characteristic dimension of the grain boundaries is several orders of magnitude smaller than the typical dimension of your "scratches" (which aren't scratches as much as actual chips, really), so the local constraint is several orders of magnitude higher along those boundaries (as cavity size and constraint are inversely proportional).
 
It really is what happens on a sub-micron scale that matters for fracturation initiation, and it's not affected by polishing.

The thickness on the other hand plays a huge role in that it determines how far a fissure has to propagate before the material breaks.

[...] due to the much higher polishing process  i have found the resulting edges to be less chippy [...]

From a physical standpoint, "chippiness" will depend on intrinsic properties of the material used, and the thickness of said material.

So if the blade has a thinner apex, it will be more prone to chipping, not less. However, your particular sharpening process and methods may result in a geometry that will both be more resistant to chipping (so a thicker apex), but that might feel sharper as explained in the scienceofsharp article.

I believe this is an interesting read at
ScienceOfSharp.

It states that aluminum oxide abrasives are sufficient, however a much finer grit than the SG-250 is suggested.

Nice find, this site really is a trove of useful information. In a pinch, it says that you have to use reasonably hard, but very fine material so you chip on a sub-micron scale. Which requires a blade made of material that can separate on a sub micron scale. Using a glass substrate makes for a hard, smooth support that ensures that the "angle of attack" of the hard particles wrt the blade remains constant and controlled.

It also confirms that the initial "sharpening" of the blade with the sg was probably more of a roughing-up of the shoulders of the apex, resulting in two fine hacksaws.