Thread: Establishing a Bevel

Originally Posted by Joe Lerch

The spine gets thicker when you progress in razor size because you need the heavier spine to support the razor.

I'm afraid that's an incorrect conclusion. The spine gets thicker with the bigger blades because it's necessary to maintain edge geometry. It doesn't take 1/2" of steel spine to support a paper-thin razor blade, Joe. Machetes take a lot more of a beating than razors, but only need a spine of approximately 1/8" to "support" the work that blade does. The spine width has been built into razors specifically to precisely maintain the edge geometry, not for looks.

Framebacks, for example, have very thin blades all the way through and the geometry was maintained by setting a built-in blade guide for honing; the frame back.

The earliest razors had to be honed without a honing guide and were built pretty much like knives. Then came the wedge grinds. Then the frameback design, then the hollow grind. From the wedge to the present extra-extra-hollow ground razors, the spine's width was always calculated to give the razor the best edge geometry for it's design when laid flat on the hone.

I simply can't go along with the notion that the spine gives us a proper angle by pure coincidence just because a big, thick spine was needed to support a thin, fine blade that was meant only to push cut hair while big bowie knives designed to hack on trees, firewood and to be used in battle require less spine than that.

Nice post guys and very interesting. I have one question if I can explain it right. On some razors the edges width is very small sometimes 1/64 to 1/32 of and inch wide. The spine's width, the width that actually touches the hone, can be wider than that of the edge. Will this cause the spine to wear away slower than the edge? Also as the spine wears away this width can increase which may decrease wear even more because of the extra metal in relation to the width of the metal on the edge. This may change the angle of honing a very little bit and may not make any difference at all. What do you think?

The "rails" that form as the blade is honed are often wider than the honed edge of the blade, but that really has no bearing on them wearing evenly as they're honed. Think of a razor as a triangle. A true wedge actually IS a triangle. A hollow grind razor is a wedge with the middle ground out. It still follows geometry like a triangle and hones evenly as a triangle, provided the pressure is even during the honing process. Whether the "rail" is wide or narrow, the edge and spine should wear quite evenly, maintaining the gemetry.

Originally Posted by PapaBull

The spine width has been built into razors specifically to precisely maintain the edge geometry, not for looks.

Sorry to stick my newbie nose in here. Hope this isn't considered rude. I've been following this thread with great interest as I want to try and restore a proper bevel on a razor. It seems then I should be concerned about not just honing out nicks but also the spine thickness to blade width ratio in case the razor was unevenly honed (spine taped or not taped)? Is there some magic angle for straights, and how critical is it to getting a great shaving edge?

Mike

Originally Posted by superfly

Found it on RazorCentral, here's the link...

http://www.en.nassrasur.com/razorcentral/archraz2.html

I think it is ment for all razors in general. Anyways, I don't care, as long as my razor is sharp enough...

For all newbies, check Artur Bohn's razor central, it has some great info on razors and shaving...

http://www.en.nassrasur.com/razorcentral/index.html

Nenad

As I told you that's a particular type of full hollow with a belly. It's not general.

Originally Posted by PapaBull

I'm afraid that's an incorrect conclusion. The spine gets thicker with the bigger blades because it's necessary to maintain edge geometry. It doesn't take 1/2" of steel spine to support a paper-thin razor blade, Joe. Machetes take a lot more of a beating than razors, but only need a spine of approximately 1/8" to "support" the work that blade does. The spine width has been built into razors specifically to precisely maintain the edge geometry, not for looks.

don't disagree with this. I think we're both right to an extent. If I showed you substantial variation in spine width for razors of the same size, what would you say. You can start by comparing a Bergischer Lowe to a sleek 5/8 razor with a 1/8 spine.

Framebacks, for example, have very thin blades all the way through and the geometry was maintained by setting a built-in blade guide for honing; the frame back.

Ok, compare a frameback to a sleek 5/8. Do you deny that the spine has to be heavier because of the more delicate blade?

The earliest razors had to be honed without a honing guide and were built pretty much like knives. Then came the wedge grinds. Then the frameback design, then the hollow grind. From the wedge to the present extra-extra-hollow ground razors, the spine's width was always calculated to give the razor the best edge geometry for it's design when laid flat on the hone.

I don't know how far you want to go back, but the earliest ones of interest to me are the true wedges. There you're honing the entire side. Is that a guide?

I simply can't go along with the notion that the spine gives us a proper angle by pure coincidence just because a big, thick spine was needed to support a thin, fine blade that was meant only to push cut hair while big bowie knives designed to hack on trees, firewood and to be used in battle require less spine than that

Any machete I've ever seen has a lot heavier blade than the thin part of a razor. You can move the front half with your fingers. That offers no structural intergrity and requires a relatively hefty spine. Once you have the minimum requirement you have the sharpest edge. If you want to make a Bergischer Lowe you have a thicker spine and a substantially different angle. I disagree with the idea that there's a precise angle that a razor is intended to have. If you're interpreting my statement to mean any more than a substantial variation in angle can result from design considerations, you're reading too much into it.

The bottom line is there's no precise angle. You can prove this to yourself by measuring the spines of different design razors of the same size. Like I said, I've been through the exercise.

Nenand gave a rule that results in a razor with more than a 16 degree angle. I've seen it stated as 11-15 degrees. That's quite a range. I think you'll find that most of you conventional razors are around 11 degrees.

Originally Posted by str8razor

Nice post guys and very interesting. I have one question if I can explain it right. On some razors the edges width is very small sometimes 1/64 to 1/32 of and inch wide. The spine's width, the width that actually touches the hone, can be wider than that of the edge. Will this cause the spine to wear away slower than the edge? Also as the spine wears away this width can increase which may decrease wear even more because of the extra metal in relation to the width of the metal on the edge. This may change the angle of honing a very little bit and may not make any difference at all. What do you think?

The thickness of the rails can be greater. If you think about it, theoretically, you remove the same thickness of metal from the edge and the spine, if your pressure is equal, so the angle should be the same when you hone normally.

It seems to me that Robert and I do the same thing if he hones the blade perpendicular and I tape. In both cases, the spine is not honed as you bring the edge to the correct width. When he drops down and resores the edge, that the first time he's removing material from the spine. It seems to me that he's taking a lot less than if he honed down the edge all the way with the spine in contact with the stone.

Originally Posted by eagle

Sorry to stick my newbie nose in here. Hope this isn't considered rude. I've been following this thread with great interest as I want to try and restore a proper bevel on a razor. It seems then I should be concerned about not just honing out nicks but also the spine thickness to blade width ratio in case the razor was unevenly honed (spine taped or not taped)? Is there some magic angle for straights, and how critical is it to getting a great shaving edge?

Robert would say yes, but I can disprove this easily by showing a group of razors of the same size with all different angles. Nenand would say yes, but I don't think it would be easy to find a rozor with a bevel angle in excess of 16 degrees.

If you agreed with them, you would have to know what angle the manufacrurer originally designe into the razor. That could be imposiible with a razor that has significant honing. I would say make it easy on yourself. Hone the edge and rails nice and evenly. Measure the thickness of the spine and the width of the blade. Try for a ratio of 5:1. That will give you 12 degrees for the bevel angle. The greater the angle, the less sharp the edge, but the stronger.

There is an ideal angle, at least as designed by the manufacturer. Different razors can have different bevels. Some shave better than others. Some maintain an edge better than others. There are lots of variables. The best manufacturers put a lot of thought into their designs and the designs got better and better, for the most part, as they got more experienced with their craft and new designs were developed and tested. There will be variations from one razor and manufacturer to another in the degree of angle, but it's not arbitrary and ideally, if it's a high quality razor, I'd recommend trying to maintain the design geometry as intended as best you can. But.... that's just my take on it. Anyone that feels their razor would be better with a different honing angle can go ahead and do that, too. If it's not my razor and it's not my face and it's not my shave, I won't insist that there's only one way to do things. To each their own. I shave with a straight razor every day and have for a long, long time now and I know what I like and what works for me and that's all I can vouch for.

John D. Verhoeven, Emeritus Professor on the Department of Materials Science and Engineering at Iowa State University discuss the same thing in his .pdf document titled: Experiments on knife sharpening.

you can find it here:
http://mse.iastate.edu/files/verhoeven/KnifeShExps.pdf

He, among other things, discuss Straight razor and commercial DE (Gillette) blade. In the both, he measures the very same angle of 17 degrees, and states a table of given angles for various tools, where he says the ideal angle for razors is 15-19 degrees. "The blade is a stainless steel blade manufactured by the Solingen Co in Germany. As shown by the end view of the blade in Fig. 8, the blade has the hollow ground surface of straight razors, which ensures that stropping on the razor strop will maintain the surface at the edge on a constant abrasion angle with the strop surface. As shown in the figure the Solingen blade will automatically sharpen to give a 2β angle at the edge of 17o. It is interesting that both razor blades have an edge angle, 2β, of 17o."