Robert sent me a Rigotti which was giving him a lot of chatter while sharpening. I worked on it for several hours with the diamond stones, ceramics and strops but couldn’t get rid of the chatter. Under the 60x loupe I could easily see a very ragged edge which was also easily discernible with a sharpness tester. No matter how long I worked, how gentle I was etc…, the edge remained ragged. The diamonds and hard ceramics were pulling chunks off the very edge. This morning I got my 800# and 1000# Choseras wet and went to work. In three minutes I had a perfect, chatter-free edge that looks great at 60x. The next step is to look at it under higher magnification and then test it out on the reeds. I wish I’d photographed it before switching to the Choseras so everyone could see the difference. I’ll report back with photos and more results as I progress…
[center]Some Images[/center]
Here is the edge after the 1k Chosera Stones at 800x:
and here it is again after 10 strokes with 1um Diamond on Leather strops:
Clearly the leather cleaned up the edge very quickly. I should have lowered the angle 1-2 degrees per side before stropping to not get as much rounding at the very edge.
I’ve got my 2k and 3k stones soaking and will do those next!
What was the reason for the chatter? Thin blade?
Also, was there any issues mounting the blade? And what angle did you sharpen at?
Mounting the knife was very easy - there are nice parallel faces and a clear grind line for indexing the depth - the blade is too narrow to use the depth key so I just aligned the grind line with the top of the vise. The chatter was from all the gouges in the edge as the diamond and ceramics were tearing out large (at least at 60x) chunks from the edge. I was using 21 degrees on the left and 23 degrees on the right.
[quote quote=“cbwx34” post=4195]What was the reason for the chatter? Thin blade?
Also, was there any issues mounting the blade? And what angle did you sharpen at?[/quote]
Here is the knife sharpened with the 2000# Choseras:
and again with the 3000# Choseras:
Wow, those pictures are drop dead gorgeous! I’m wondering, though, why the diamond and ceramic stones tore out chunks from the edge and the Chosera’s don’t.
Clay,
I have found that going with higher grit stones (i.e. 10k and up) give a “damped stroke” and produces a keener edge (IMHO). Also, keeping them damp with DI and clean helps tremendously.
I think the difference is in the hardness of the abrasives and how they’re bound in the matrix.
Here is the knife sharpened with the 3k Chosera stones and then stropped lightly with the 1um diamond and leather strops:
All the chatter has been eliminated and I can run the sharpness tester along the edge and feel no bumps at all. It is scraping reeds exquisitely and although I have no real experience with reed making, I can tell the the control reed makers will have is very fine.
Overall, I think the Rigotti knife I got to play with has some flaws in the heat treatment making it very brittle, especially in a one inch section along the middle of the blade. Using the Chosera stones, I was able to overcome the problem and create a very straight, refined edge.
Actual Reed knife talk!!! :cheer:
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!
B)
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:
[quote quote=“wickededge” post=4246] 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.
I decided to widen the angle by two degrees per side and re-strop the knife with the .25um Diamond on Leather Strops:
[/quote]
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.
[quote quote=“cbwx34” post=4247][quote quote=“wickededge” post=4246] 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.
I decided to widen the angle by two degrees per side and re-strop the knife with the .25um Diamond on Leather Strops:
[/quote]
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![/quote]
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.
[quote quote=“Rhautbois1” post=4752]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![/quote]