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Thread: Taping the EDGE
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11-26-2008, 12:51 AM #21
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Thanked: 77
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11-26-2008, 02:31 PM #22
If I were to come across a razor that had that had uneven wear on the spine I would probably pass on it unless it was a make or model I really wanted badly. In that case I would probably send it out for a regrind rather then trying to restore it myself. Edges are one thing but spines are for me a horse of a different color.
One more thing that comes to mind is my father telling me years ago that the further up you get into the blade of a pocket knife the temper changes. When you get a pocket knife that is honed to the point where the edge is now up into the belly of the blade the temper is not as hard as it was in the original edge.
I am not sure if this is correct but it made sense to me and if it is correct that means that the spine may be softer then the metal at the edge and wear at a faster rate if not taped. More knowledgeable members on the mysteries of temper and metallurgy will no doubt correct me if I am wrong.Be careful how you treat people on your way up, you may meet them again on your way back down.
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11-26-2008, 04:03 PM #23
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Thanked: 150There's really no way to generalize about how much of the edge can be honed away before the steel qualities begin to change (from regions of varying hardness).
But there is a key difference between straight razors and pocketknives that may be relevant; razors are intended to be honed laying flat, so the spine ought to be a similar hardness to the edge to minimize unpredictable hone wear, whereas pocketknives are only honed on the cutting edge, so the spine may be tempered to a lower hardness to facilitate a "tougher" blade by reducing the amount of brittle Martensite.
So for all intents and purposes a straight razor ought to have a uniform (or very close to uniform) range of hardness, a range that probably doesn't go out of the bounds of usability.
As for the test results of 9 to 18 degree bevel angle acceptability, that may or may not have been an experiment I did, but my results were more like ~12 to ~22 degrees. I made a series of razors that had bevel angles in that range and gave them all edges from the same progression of hones to see how the angle affected shave quality. I even took the ones with very acute angles and honed them with multiple layers of tape to identify the angle that was too large for the given piece of steel. The results were in the above stated range, with very little detectable difference if the angle was kept reasonably close to its original condition. The biggest difference was in the initial quality of the steel.
So while its good practice to keep a razors geometry as close to original as possible, the razor's performance isn't going to be adversely affected by an extra degree or two of bevel angle and may be perfectly fine with a few extra degrees more.
To each his own, I suppose.
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11-26-2008, 04:12 PM #24
Good point regarding the difference between pocket knives and razors. Thanks for the blade angle tests too.
Be careful how you treat people on your way up, you may meet them again on your way back down.
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11-26-2008, 09:17 PM #25
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Thanked: 77OK! for a relative feel
My 5/8 Dovo Micarta has (roughly) the following dimensions:
15.875 mm from spine (where it contacts layed flat) to edge
5 mm spine width
That's going to give me an approximate bevel angle of 18.12*
If I were to tape the spine and lose 1/8" of blade, the bevel angle would go to 22.71*
If I were to tape the edge and lose 1 mm of spine width the bevel angle would go to 14.48*
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11-26-2008, 09:46 PM #26
So would it be that the steeper the bevel becomes the closer the spine should be to the face?
I feel sorry for the early retirement of a razor by abuse and neglect, but not guilty enough to feel the need to resurrect one. I think they could be made to feel useful as box cutters
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11-26-2008, 10:07 PM #27
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Thanked: 77Well, yes. But I think the assumption is that the spine wears and gets thinner as the edge wears and gets closer to the spine. So the bevel angle is maintained closer to what it started as the razor wears.
But from the observations in the above posts maybe it's not an immediate crisis if you always tape the spine as opposed to wearing the spine down as the blade width decreases.
We still haven't heard how exactly blade makers design the geometry. Does Dovo manufacture their Micarta razor to have exactly an 18.2* edge angle? Or would anything between 12* and 21* pass QA? (primarily determined by spine width). Do they even consider how the geometry changes as the razor wears? If you asked Dovo what they thought about taping the spine as you maintain your razor for the next 50 years, would they say "absolutely not!" or would they say "eh... it doesn't really matter"?
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11-30-2008, 05:25 AM #28
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Thanked: 150Fwiw, blade angles greater than ~22 degrees may be perfectly fine, depending on the individual qualities of the razor's steel, I just know that 22 deg. is still a very usable angle for all intents and purposes.
In other words, don't throw away a razor just because it's bevel angle is greater than some number you've heard reported, test it for shave worthiness first.
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12-05-2008, 09:26 PM #29
Here here Russel, after all, isn't the shave test the ultimate deciding factor?
I'm sure there are optimum angles and all, I mean clearly tests have been done to prove such. But really shouldn't it all come down to how well it shaves?
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12-05-2008, 10:59 PM #30
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Thanked: 77I think that's what Russel said. Don't throw it out if it shaves well just because the angle is out of the "norm". Russel's observations were that the bevel angles from the mfgs fall in a relatively broad range. Broad enough that a degree or two of change isn't that significant. Another interesting implicationthat Russel made was that an optimum angle is corrrelated to the characteristics of the steel.
Surely personal shave angle would be a factor as well. Someone who shaves with a greater angle than someone else would get different results with the same edge angle. If you really wanted to get precise I suppose you could optimize the bevel angle to not only the steel but to the individual shaver as well . LOL, that could be the next SRP service. Personal razor fitting, right down to the optimum edge angle for you.