Actual Reed knife talk!!!

The diamonds cut through the steel MUCH deeper than the Choseras in general, and the Rigotti knives aren't very hard to begin with (they are a standard beginner's knife), so lower grit diamonds plates were pure overkill in this situation.

While it is interesting to see the differences in performance between the diamonds and Choseras, the edge shouldn't chatter based solely on the use of the diamonds or ceramics vs. the Choseras...

In my experience, the chattering is a combination of the thickness of the blade at the edge being too thin (usually a full hollow ground straight razor), and the edge shape and angles being off. Rigottis usually have enough meat, so it must be an angle thing.

I just looked at my Rigotti hollow ground, and the "resting angle" is about 20 degrees per side. I used the angle cube to check what "my" angles would be, and they work out to be about ~23 and ~27. If you wouldn't mind, go back to the diamonds with the right hand paddle at 27 degrees and keep the left hand one at 23 degrees. If you do a bunch of light alternating strokes and end with the right hand, it would be what the edge would look like after using the WEPS.

In retrospect, when at the IDRS show, I suggested 21 and 23 degrees to Robert, and he ran into a similar problem, and the only solutions were the steel was crap, or the angles were too low. We were on opposite ends of the room, and I didn't get enough chance to play with it or focus on it. Thanks for looking into it more, Clay!

I used the 23/21 degree profile and checked the edge with a 60x loupe throughout. It was very easy to see where the metal was coming off in chunks with the diamond and ceramic stones. It was interesting that effect always occurred within the same 1" range of the blade - the blade on either side of that one inch section didn't experience any of the micro-chipping. I could clearly see that I was reaching the edge with each grit and watched hunks of metal continue to peel off. The Choseras cleaned up the chipping right away.

After the .25 Kangaroo strops, I went on to sharpen the knife on the 5000# and 10000# Chosera Stones. I was surprised to find the edge a little ragged afterward though it was still wonderfully sharp:


Zoom
After sharpening the Rigotti on the 10000# Chosera Stones I went back to the .25um Diamond on Kangaroo strops and got a very nice result:


Zoom
I lowered the angle significantly before stropping the knife to prevent any convex shaping, which worked out really well but didn't clean up the knife edge as much as I'd like so the next step will probably be to strop the knife again a few degrees wider per side.

At this point, the knife is so sharp that its weight alone is almost too much pressure on the reed and I have to pull back a little to only take a single fiber.

I decided to widen the angle by two degrees per side and re-strop the knife with the .25um Diamond on Leather Strops:


Zoom

wickededge wrote:


Hate to do this (again) but could you be a little more specific? "lowered significantly" doesn't say much. And I'm really interested in the "widen the angle by two degrees...". do you mean 2 degrees above what you sharpened it at?

Thanks!

Ah yes, details I had sharpened the blade at 23/21 degrees. In that last round of experiments I lowered the angle to 20/18 degrees which worked out pretty well but didn't get quite to the edge enough to clean it up so I widened it back out to 22/20 degrees which seemed to work well without too much convexing of the edge.

cbwx34 wrote:

Thanks mucho!!

Mark - it seems the Rigotti's are made with a brittle steel. Some of my older Rigottt's will sharpen with diamond stones but the newer ones simply won't. The knife Clay sharpened was the worst of the bunch - I called it my 'chatter-baby'. Many oboists however use the knives and it was critical to find a solution.

Did some more work on these knives today and took pictures at 800x:



I sharpened the knife with the following progression: 2k/3k and 5k/10k Choseras followed by the 1um Diamond and Leather Strops.

Clay - I was delayed getting out of town and was very excited to see the package from WE - just arrived this afternoon.

I took a look at the blades and tried them out this evening. They are absolutely fantastic!!

My one concern is how they would respond to the steel. As we discussed - I used a steel often to reset the burrs as the cane dulls the edge immediately. I am very happy to report that there was no problem with resetting the burr on the steel. Was very concerned that the steel would cause chattering - but thankfully - no.

Last night I started two new reeds and they gave me quite a bit of trouble. With the knives you sharpened they shaped right up with very additional little work. There is a saying that three secrets of a good reed are 1) a sharp knife 2) a sharp knife and 3) a sharp knife.

Thanks so much for taking the time with these knives. Can't wait for my Chosera's to arrive!

I'm glad to hear it! I think you'll love the Choseras.

Rhautbois1 wrote: