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So until now I've been getting by on bread knife sharpening by ... not really sharpening, but by using the SchleifJunkies' "leather wheel for serrations" and the edge of a belt to strop serrations.  I was using 1 micron diamond on the wheel and PA-70 on the belt.  Worked okay, but not really satisfactory for a dull knife.

This morning I leveled it up, using 20 micron diamond on the wheel, and I'm pretty happy with the result!  I was sharpening a Mercer bread knife with roughly 1/4" serrations.  Before sharpening, it measured at around 300 BESS.

I did 3-4 passes on the bevel side at the measured edge angle (25°) and then stropped on the edge of a leather belt with PA-70.  That got my BESS reading down to 110-125g, which to me is more than acceptable for a bread knife.

Now, I don't know how it would work with a really dull knife, and it's obviously not going to restore a knife with rounded points, but that's a topic for another day.

https://schleifjunkies.de/en/product/leather-wheel-for-serrated-edge/

Plus I realized afterwards that a serration is not a half-circle, but rather a portion of it, so the diameter can be wider than the pitch.
...snip...

A radius gauge set, like below is the right tool to measure the serrations. Match the curvature of the gauge to any portion of a internal or external radius and read the measurement from the stamped markings. 

Thanks!

14mm is .55", which seems about right for most bread knives

Well my typical bread knife is akin to this one.

It has 35 serrations in less than 8.25", which is at most a .24" pitch.

On this other one, it looks like a .25" pitch at best (31 serrations in less than 8").

For both, the wheel will ride on the teeth.

Wolfgang demonstrates using the edge of the wheel with what looks like a 3-ish mm corner radius, which seems more like it. Typical triangular ceramic rods have an even higher curvature.

Yeah, those are smaller serrations than the ones on the Mercer bread knife I'm using.  I looked at a couple others we have and they are smaller.  I guess you'd need at least two sizes to cover all the bases.

After you use the angle setter you mat want to try coloring the knife edge with marker and rotate wheel ny hand to see what is removed. This is a double check on the setting.

I ALWAYS do this, no matter how I set the angle.  On EVERY blade.  On EVERY wheel diameter change (and even between Tormek diamond wheel changes where the diameter doesn't change). 

Yes, that. It is a tremendous help when it comes to gauging what the motion has to be to sharpen the tip (and heel) properly.

Agree!  In tricky cases I always Sharpie the tip and heel -- just around 1/4 - 1/2".  No need for the whole blade in my case, because I'm rarely trying to match an existing angle.

Yeah, this is a problem for Tormek sharpening.  If you angle the knife you are going to get wildly different sharpening angles from the heel to the tip.  Like BPalv, I'll either use a 1x30 or freehand sharpen these types of knives.

Yes, I agree that the very high edge angle is the cause of rapid dulling.  An edge bevel is essentially a triangle, with the acute angle forming the apex.  The wider that triangle is, the faster the apex will widen out through abrasion. 

On the other hand, a very thin triangle is more susceptible to rolling and chipping, so you have to balance acuteness versus edge stability.

Personally, I use 15° per side for most kitchen knives, but I know many pro sharpeners do 17°, and some go as low as 10-12°.  It's something I'd explore with your client.   

I hope I got that kind of basic math right, but I'll wager "R7" means a diameter of 14mm.

So for all knives with serrations spaced less than 14mm apart (which incidentally means all of my bread and frozen food knives), this wheel will grind the apex of the teeth and not the space in between the teeth.

14mm is .55", which seems about right for most bread knives.  I know that Cliff Curry sells a 6" by .5" CBN wheel for bench grinders that he recommends for bread knives.  Of course that's going to be more for cutting in new serrations as opposed to touching up existing ones.

Anyway, I'm going to order a pair of the SlipaKniven wheels when they come back in stock and will report back.

Interesting product!  I think these would also be quite useful for sharpening recurve knives.

Joe, what angle are you using to sharpen the knives?  You should know that it's much easier to achieve low BESS scores with lower edge angles.  Most of Vadim's commercial sharpening was done at 12° per side.  It's possible to achieve very low scores with higher edge angles, but the higher you go, the lower the margin for error.  Also keep in mind that while Vadim recommended higher honing angles for lower-end steel, he always had at least a two-step honing process, with the final pass(es) at the exact sharpening angle.

Regarding compounds, for regular kitchen knives I think PA-70 is a better choice than 2 micron diamond, if you're only using one compound.

Paper Wheels with diamond paste & oil do not overheat an edge.
Vadim's research & testing also proved that.

A Paper Wheel using the standard silicon carbide grit will also not overheat an edge, provided you use enough wax on it's surface so there is  a complete coverage.
This is critical, and the wax is best applied like a crayon on a wheel that is turned by hand.

I gotta say, if you pull your knife across the wheel less than 5 mm a second I think you would still possibly hurt the temper.  I think that is documented in Wootz's work.
IMHO it wouldn't take much to heat a quarter micron thickness at the apex.

Yes, if you go too slow you can absolutely smoke an edge, and it also depends a lot on pressure.  Part of my problem is that every paper wheel I've tried has been slightly out of round and it takes some pressure to keep the edge from bouncing.  I just don't see an advantage over leather belts, which produce very little heat.

I use a one of those rubber sticks that are generally used for cleaning abrasive belts to clean my CBN wheels.  I use it after every sharpening and have had zero problems with load up.

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I've been using the KS-123 for a few months, after a couple years using the calculator method, measuring to the top of the case.  I find the two methods equally accurate (to within about .5°), measured using a laser goniometer. In other words, .5° is the maximum divergence I've seen.  On average I'd say the set angle is coming in within 1/4° of the actual angle.

For the most accurate results with the KS-123, I find that I do have to recheck the angle after tightening down the USB.  Even though I push down on the USB when tightening, I generally get a +0.5° shift.

Just to add another voice, I've also not had much luck recreating Vadim's results with felt wheels.  Nor did I using paper wheels, which I generally don't like anyway due to rapid heat build up.  I do my post-sharpening stropping on a Ken Onion with the blade grinder attachment.  For common steels, I do a couple passes with a leather belt and 1 micron diamond at +1.5°, followed by a couple passes with another leather belt and PA-70 compound at the sharpening angle.  That usually nets me a sub-100 BESS score, although sometimes it takes a minute or two hand stropping (.5 micron and/or .25 micron) on bass wood to get there.

Schleifjunkies sells a line laser and holder for Tormek.

The aluminum CBN wheels can be purchased on AliExpress or Amazon.  I'm sure it's the same manufacturer. Same goes for the pricey resin-bonded wheels.

The plastic-hub wheels are also very good, but because the CBN is electroplated to steel, they are more prone to corrosion.  Woodturners Wonders advises against using them in water, but I've been doing it for well over a year without any problems (and no corrosion inhibitor).  But my wheel isn't sitting in water all day, and I dry it off after each use.