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I`ve been thinking about the trigonometry of a razor. If the spine of a razor is the same width no matter what depth the razor.
Then when honing the razor the angle at the edge of a deeper blade would be much shallower than that of the smaller razor.
I don`t have that much experience in the world of razors maybe deeper razors have thicker spines. I would be interested to find out either way.
this is a math problem - the ratio between the spine and the width is also known as the bevel angle.
there are several big threads on this, along with many actual measurements.
look them up.
bart from coticule.be has an angle calculator that works great for that sort of thing.
Larger razors tend to have thicker spines. There is some variation in bevel angle among razors, but there are big razors with narrow angles and big razors with wide angles. Most razors seem to be somewhere in the range of 15 to 18 degrees.
Yeah, as gugi stated, this has been combed over before. I have razors that are less that 1/2 inch wide with spines you could almost sharpen and shave with, and 8/8 blades with a spine over 1/4 inch wide. It is relative to the optimal bevel angle, and a very interesting topic to research. I have a few razors that have relatively narrow spines that I want to try narrowing to less than 4/8 just to see if the loss of blade width throws the geometry off enough to alter the edge. Happy hunting!
Might want to read about real razor angle measurements right here
http://straightrazorpalace.com/razor...zor-angle.html
Degree of hollow grind, I feel is more of a factor of sharpness. No scientific proof, just my experience:shrug:.
lesser bevel angle can equate to bigger bevel, so number of geometrical factors to consider. Full hollow and singers, extra hollow seem to get better with initial few hones in my experience.
It has been explained to me that the ratio of spine thickness to blade width should be between 3 and 4 with 3.5 (whoda guessed) a reasonable average. So a 7/8 razor should have a spine thickness of about .250" and 6/8 would want a .215" spine, where a bit thicker is OK. For honing, thinner spines than that seem to allow for more delicate edges which can be frustrating for us apprentice whetters to successfully deal with; the journey and master level honers among us may not be as potentially vexed.
:beer2:
Again I mention that one should really read that thread I linked with actual measurements where it will become apparent rather quickly that there are no hard and fast rules or ratios...
The numbers are really all over the place but the average seems to be about 16 degrees as to the "Best" I really would not venture a guess...
The angle and bevel width in relation to sharpness has no relation, the quality of the steel is much more important... Razors only get so sharp, period and many/most can get there, the only question is how smooth they are at that sharpness level...
BTW please feel free to add more measurements to that thread, as you can see the more data we have, the better the conclusion becomes...
I've had razors from 7 1/2 degrees up to 25 degrees. Below about 16 degrees the edge doesn't hold up as long but does seem to be sharper. Above the normal range the razor still seems to shave fine, but the razor is heavier than it needs to be. That one razor with the 7 1/2 degree edge was absolutely sick for about two strokes, at which point big chips started appearing in the edge. My Hart has a 13 degree angle and won't hold an edge for more than about 5 shaves. And on the upper end of the scale I've got a razor that I had Josh Earl make me that is a 5/8 with a 25 degree honing angle, that shaves fine and holds an edge fine, but weighs nearly as much as a 7/8. The commercial guys all seem to have gone with steep angles as well - Gillette cartridge blades have a 28 degree honing angle on them, and apparently the Feather blades have a 25 degree angle.Quote:
Originally Posted by blockhead
So I guess that I would be fine to narrow these blades, as this would increase the bevel angle. I have a razor that I have been working with on the hones that seems to dull very quickly, and was thinking about throwing some tape on the spine to see if I could tell a difference in the resulting bevel angle. Just to see if a few layers of tape would maybe make a difference in the longevity of the edge.Quote:
Originally Posted by mparker762
More than a few layers of tape will affect the stropping in a way that will negatively affect the longevity of the edge, and taking the width of the blade down to 4/8 or less will make it harder to hone so it'll be harder to get the same level of sharpness. IME longevity is so heavily affected by stropping that it's hard to compare razors, because if your stropping is bad then your edges won't last no matter what the honing angle is. Once you get your stropping down then edges will last many months, but this means it can take many years to get a good comparison of just two razors, and you really need to test a bunch of them to make sure it's the angle that's affecting the longevity and not some other variable.Quote:
Originally Posted by blockhead
The only way I can think to test this in a reasonable time frame without involving the stropping variable would be to make several razors out of the same stainless steel, with say 17 degree and 25 degree angles, and just don't strop at all. In theory this would put you on the same playing field as the cartridge razors who can get a week o so out of an edge without stropping, and would give you a fast enough turnaround time that you could perform a good number of tests in a reasonable amount of time.
Personally, I don't think the higher angle makes a practical difference in longevity for HCS razors, with good stropping my edges last for 3-6 months of daily use, and other can get a year or more out of a single edge, and HCS razors must be stropped in order to keep the corrosion in check.
I think the more useful application of this is in stainless razors, because they don't have the corrosion issue the way HCS blades do, so a higher angle blade could get you a long edge life without much stropping - this works for the cartridge blades after all, which can often last two weeks to a month without stropping, and it seems quite possible to me that a stainless straight razor should be capable of going many months with only occasional stropping, basically stropping would become something you do as a touch-up instead of as a daily (error-prone) task. It is interesting that in their patents Gillette claims that 28 degrees gives you the sharpest edge on stainless steel. Not just a long-lasting edge, but actually the sharpest edge. I don't know if what they really mean is "sharpest edge using our variable-diameter helical-wheel 3600rpm honing machines" or if their experience is applicable to hand-honed straight razors. But it's an interesting data point, and it would be funny if the reason stainless steel never took over straights the way it did DE and cartridge blades is because the straight makers kept making stainless razors using the geometry that had been optimized for HCS razors that turns out to have been extremely suboptimal for stainless.
I guess I was looking at it from the perspective that if I narrow the blade, and retain the thicker spine, it would increase the angle of the bevel. Are you saying that a blade 4/8 or less would be harder to hone because of this added spine thickness? Bear in mind, it is not a large amount of added width to the spine. Not as though I am jumping from an 8/8 to a 4/8 and having to deal with a 1/4 inch thick spine. More like from a 5/8 or 6/8 to a 4/8. I have blades that are narrower than 4/8 that have no problems with taking an edge. Comparatively speaking, they seem to have the same bevel angle and width as my larger width razors, just scaled down proportionally to fit the smaller size razor. Now, if I wanted to increase the bevel angle of the smaller razor, couldn't I do that by adding width to the spine? This would also alleviate the problem with stropping, as you would not be removing the extra width as you would when you hone with tape, right? Am I looking at this correctly, or not? Wouldn't it be just a few steps away from a scaled down hollow, and a few steps toward a smaller version of a wedge (or 1/4 grind)? One of the razors in question has a smile that is wandering into the belly or swell above the edge. I wanted to take it down to just ahead of the belly and see if I could do away with the rounded tip and the smile. I had been thinking that it was doable, but I have been wrong before.