Author: oboedrew
Date: 2011-04-18 23:01
BBoard, I'm crushed. Returning from a short absence (taxes!), I expected dozens more knife-sharpening posts. I was excited to leap back into the fray with guns-a-blazin'! :-) Now I'm confused. Why do we have so many posts in so many threads on gouging, yet so little to say on this weightier topic? Hmm... wait... nevermind... I think that question just answered itself. *winks*
huboboe wrote:
> If you are going to put a burr on your knife edge, try
> taking a page out of the woodworkers instructions
> for sharpening a scraper, used for several hundred
> years to put the finest possible finish on wooden
> furniture. They take their square, thin sheet of
> steel, flatten it on a stone and then curl the edge
> with a smooth, hardened burnisher, producing the
> burr that does the cutting. In our case we should
> get a fine, sharp edge on the knife first, then use a
> burnisher (or the edge of your steel plaque) to curl
> that edge into a controlled burr in the direction (left
> or right handed) you prefer. It doesn't need to be,
> and shouldn't be, very pronounced to work."
Agreed. Every good scraping burr starts as a cutting edge. By now we're all clear on that... right, BBoard? *crosses fingers*
Of course, once that cutting edge is formed, there are MANY ways to craft a burr. Fine ceramic sticks and stones, honing steels, and hard/black/translucent novaculite all work nicely. And let's not forget every reedmaker's ol' standby: a fine aluminum oxide benchstone that's all clogged with swarf from years of use without oiling or cleaning. It's mostly personal preference... and mine varies from time to time.
By the way, Bob, I loved the analogy to card scrapers. Props.
huboboe wrote:
> I'm opposed to sandpaper and many diamond stones
> because, even if the abrasive grit size is quite fine,
> the distribution is such that the surface it produces
> is a series of parallel scratches which result in a
> sawtooth cutting edge.
Ah, but all stones do that! It's how they sharpen. The finest diamond stones I've seen are DMT's 9 micron and 3 micron stones (in American terms, individual particles about .000354" and .000118" wide, respectively). I haven't tried the latter yet, but I've used the former to put a serviceable (not spectacular) edge on bevelled knives. To be clear, they're not ideal finishing stones, and they're especially bad for turning burrs... but it's not because they produce tiny parallel scratches. Oilstones and waterstones do that too.
huboboe wrote:
> I like to sharpen a beveled edge on a relatively thin
> blade, like a double hollow ground blade, and have
> it sharp enough to cut a clean chip, like a plane.
Now THIS is an interesting wrinkle. For a span of about a year, I sharpened my Landwells as you've described. A microbevel on the trailing side of a hollow-ground blade has some limitations, but it can get the job done. The edge geometry is right for scraping. It's not as precise as a fine burr, but it's not as clumsy as our conventional bevelled reed knives. I think it's somewhere in the middle, depending on the specifics of the bevel.
I guess it's worth mentioning that burrs and bevels aren't mutually exclusive. Some reedmakers intentionally form a burr at the end of their bevel. Others do so unwittingly.
huboboe wrote:
> I only use one knife for everything except
> cutting the tip, where I use a straight razor blade.
Bravo! Reedmakers, remember: God drowns a kitten every time you clip with a scraping burr.
huboboe wrote:
> The major error I see in my student's (and in my
> own) sharpening technique is rushing to a sharp
> edge by steepening the angle of the blade to
> avoid honing the entire bevel behind the edge.
> And then again, and again, until the flat bevel
> that ended in the sharp edge is now round and
> requires a long session with a coarse stone to
> restore the original profile.
Sound advice.
huboboe wrote:
> Drew and I can go back and forth on the merits
> of a burr vs a clean edge and let the sandpaper
> folks talk about 1200 grit vs 2000 grit wet-or-dry.
Hmm... I wouldn't characterize the debate as "burr vs clean edge," as that implies scraping burrs are somehow messy, or sloppy, or whatever is the opposite of clean. A scraping burr is an instrument of surgical precision. I look at bevel vs burr chats more like this: "Do you want to work at the oboe, or do you want to play as naturally as you speak?"
Wes wrote:
> However, I once got a good looking counterfeit
> Vitry knife with no name on it that simply could
> not be sharpened and could not be used to
> make reeds.
For what it's worth, some (perhaps most) of the "Vitry-style" knives available in the US nowadays are from Rigotti. A couple of my students have used them recently. I've had to grind slightly convex blades flat upon arrival; but after that, they hold a pretty good burr.
Oboe Craig wrote:
> Also still refining the Speedy Sharp techniques and
> things are improving there as well.
Ah, I left that off my list! That Speedy Sharp is so dang gimmicky, but it can turn a decent burr, if used gently. Still... not my favorite gadget.
Alright, that should be enough to get the ball rolling again, eh?
Cheers,
Drew
www.oboedrew.com
Post Edited (2011-04-18 23:06)
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