Straight razor shapening question

A

amw308

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Jun 20, 2003
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I read the "Sharpening FAQ" by Joe Talmadge. I might be mistaken but i think he mentioned that a razor blade is sharpened to a chisel edge. However, I have read other tutorials contrary to that. Does anyone have an opinion about what type of edge is best for a straight razor?
 
The straight razor is used on both sides, so it's created with an extreme hollow grind and sharpend with a dual-bevel. The angle is critical as is a super-fine edge and stropping. There are a couple of GREAT shaving forums out there as well as some tutorials. I don't have the links handy, tho...:foot:

J-
 
Yup, sharpened flat to the abrasive (spine rests on abrasive) on both sides.
 
I'm professional oboist and use mainly double hollow ground knives to scrape the reeds. Recently I've been reassessing my sharpening technique and abrasives and am quesitoning the same topic. I've been at this for 30+ years and learned from players in the major orchestras and some knivemakers who serve our community. And none of them agree on techique or angles or abrasives! I find that this is one of the more difficult things to teach!

I have learned that one should sharpen at 0 degrees on both sides to get the edge (knife flat on both sides); sharpen with both sides raised about 20 degrees; with one side at 0 degrees and and the other raised about 20-30 degrees; one side raised about 10 degress and the other about 20 degrees. That covers every relationship I think.

In any case, at the end we raise one side a bit more to get a push-edge for scraping. All of these techniques seem to work but they do wear on the knife differently and eventually the blade gets too thick to keep a good edge for scraping. I recently bought a Tormek grider to see if I can prolong the knife's lifespan or hasten the process when the knife can not be rehoned or maintained.

I would be very interested in input from people who really know knives. I think that sharpening is not a big enough part of musician training.

http://www.squidoo.com/oboereedknifesharpening/
http://www.squidoo.com/oboereedmaking/

I made these sites for my students, maybe they would be helpful to someone.

ann

PS What are those shaving forums anyone?
 
annr: Before we can talk about sharpening, you have to tell us a little bit more about the process of the scraping of the reed....I doubt many will be familiar with this process :D.

Sharpening should always depend on the application. A straight razor is used both in "forhand" and "backhand", so the edge must be symmetric. For maximum pushcutting ability it needs to be a very thin profile at the edge while spine thickness is largely irrelevant to the shaving process, so you can make the spin so thick as to serve as a sharpening guide and to give the blade stability. The hollow grind is ideal for this application. However, there are three types of razor grinds: 1/1 full hollow, 1/2 full hollow, and wedge. The wedge grind has not been used for a long time, it is essentially a full flat grind. The problem with the hollow grind is that if you take it to the extreme the blade becomes so thin that it loses stability. So in a 1/1 full hollow, the blade is ground with two wheels of different diameter so that a ridge of slighly thicker material runs parallel to the edge about 1/4 ways from the edge towards the spine. This ridge gives the blade the necessary stiffness at the thinnest profile possible. A 1/2 full hollow does not have the ridge and hence as to be ground thicker in cross section to achieve the same stability.

But I degress. The woodworkers use specific scraper blades which are ground at very large angles (close to 90 deg included) because the edge scrapes but doesn't cut, so cross section is not an issue, but since the scraping process involves large lateral forces, edgestablity is essential. However, if the reed sharpening process is more of a planing process, it would make sense to sharpen it similar to a planar blade with a single bevel and a small relief on the back side. The angle of the edge would then depend on the hardness of the material, depth per cut and the planing angle (the angle between the blade and the work piece).

So if you could give as detailed a description of the actual reed scraping process, there will be many people here who will be happy to help you find a resonable sharping process.

Oh, I forgot: go to the main page and find the subforum: "straight razor and grooming" or something like this, should be pretty obvious.
 
Thanks for the good questions and interest in my subject! :) I looked at the profiles of the blades and can’t be sure that these are the 1/1 full hollow ground. I don’t think I see that ridge running parallel to the edge so I included a link to a photo of an example of what has been industry standard for many generations. Maybe you can tell - tho not a great photo.

http://www.mmimports.com/catalog.cfm?Action=ShowProduct&ProductID=191

I see that I do have other knives that sound like the wedge you describe.


Re: The scraping process and other details.

The material, cane, is actually a form of grass. It has at thin, outer layer of bark and several under layers that get softer and pithier the deeper you cut. The initial total thickness ranges from .45mm- .6mm (with a double radius gouge) and .5mm-.01mm when finished. The deeper you cut the more difficult it is to scrape without ripping or nicking the cane. Cane varies in texture and hardness from batch to batch.

Depth per cut: This is difficult to quantify. I would say that after the bark is off, 5-6 strokes would remove about .1-.2mm of cane depending on the pressure of the knife and the segment of the knife used. In general we try to use the weight of the knife to remove material. In the finishing steps, in the pith (the tip of the reed), I will remove “shavings” that are smaller than dust. We want the cane to come off in smooth curls rather than small clumps.

Planing angle: The motion used is the rotation of the wrist back to front, so that the length of the scrape can be almost as long as the arc created by that movement, or only a very tight “wiggle” of the wrist. We must lift the blade slightly between scrapes. A backwards scrape would tear the reed.

The neutral position of the blade w.r.t. the cane is about 90 degrees. The various motions and cuts are described as scooping, planing (there is always a tiny back stroke to get the knife going), severing, blending and dusting. We scrape straight ahead, and at angles. Sometimes we deliberately put nicks in the cane, but usually this is not desirable.

The knife needs to be very sensitive and “feel” the unevenness in the scrape. The reed has several areas and goes from bark to thin to thicker to very, ultra thin at the tip. These areas are discreet yet united. We set up a series of vibrations that we can inhibit or enhance and the tip is so thin to control the start of notes and the luster of the sound.

The surface of the reed is curved, from a segment of cane 10.5mm in diameter. The reed has two blades that lie back to back with an empty chamber between them. The air passes through this chamber and into the instrument via a metal staple.

The general dimensions of the cane section is 25mm x7mm x 1.5mm ( the opening)

**To scrape on each blade individually one must use an insert a metal plaque between the blades to support the blade that is being scraped. The knife’s edge comes into contact with this metal on almost every scrape. If you watch a pro make reeds, he will touch up his edge about every other scrape.

I hope that this isn’t too much information and look forward to your response.

Annr

Ps We have a saying that it takes only a few minutes to make a good reed, and a few minutes and a second to make a bad one! Actually it takes more than a “few” minutes and you may get a good one -or not.:D Thanks for the shaving links as well.
 
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