Spine wear

Hi Folks,

(And yep, friendly and interesting discussion).

What I don't understand is why we're talking about the width of the bevel - sure, that can widen (and it partly depends on the blade grind geometry), but what difference does that make to the angle at the edge?

Here's what I mean. First pic of how I see honing without tape (I "borrowed" the original image from somewhere on the web - only the red lines are my own work)...

12220267343_a3cd221dc6_o.jpg


And this is how I see it with tape...

12220267393_4ece8484b9_o.jpg


It seems obvious to me that the second picture shows the angle at the edge getting steeper (never mind the bevel width - that's not relevant).

Can anyone explain, preferably with illustrations, how I can be wrong here?

Cheers,
Alan
 
mikew said:
Just to illustrate this, if you ground a 6mm thick piece of steel to a sharp edge at 20 degrees per side the resulting bevel would be 8.242mm wide. If you added one piece of electrical tape to give a thickness of 6.09mm and maintained the same grinding angle, the bevel would be 8.366mm wide. That's a .124mm difference! On something as thin as a razor we are talking about even smaller changes.

Of course, I could be wrong about this! I'm just going on my own experience :)
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No question of making enemies Mike.

I think you have this slightly wrong in that the tape thickness needs to be doubled up as it covers both sides of the spine. I use about .15 for thickness so if you are using a fairly extreme 3 layers you have increased the spine width by 0.9mm - that is significant if you are starting at something that can be as thin as 5mm.

To give you a practical example using a blade 18mm wide - if the spine is 5.3mm then 3 layers of tape will result in a 19.6 degree bevel. Using the same calculation on a blade just a couple of mm thicker i.e. 5.5mm, then 2 layers of tape gives an angle of 19.3 degrees. Without any tape at all the bevel angle will be 16.7 in the first example - still within acceptable bounds for shaving, but a noticeable difference in bevel width.
 
Wow after reading these I'm glad that you "all" agree: New razor 1 layer, 30£ razor 2 layers, 20£ razor 3 layers, 10and < 4 layers.
Makes the old new again.
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Oscroft said:
Can anyone explain, preferably with illustrations, how I can be wrong here?

Cheers,
Alan
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I think your illustration already proves the point - look at how much additional metal is removed at the edge when you don't use tape. In fact, I think the second illustration is wrong - you hould start the lines off including some tape so that they converge a lot closer to the existing edge. Also you are right, the angle will increase when tape is employed - that's exactly what you want in order to avoid an ever-increasing bevel width.
 
Hi Oscroft, I hope I am understanding your question. The sharpening angle is set by the thickness of the spine. If the spine was say 2mm thick and so was the edge, when you lay the razor on the stone you would be sharpening at 0 degrees.

UkRob, yes I can see an extra .9mm would make a difference. In my example I was referring to the the bevel angle per side so 40 degrees inclusive.

What would you say in real terms the difference would be between a bevel set at 15 degrees and one set at 25 degrees. Of course it would look different but how would it effect shaving? After all that's the important bit right?
 
mikew said:
What would you say in real terms the difference would be between a bevel set at 15 degrees and one set at 25 degrees. Of course it would look different but how would it effect shaving? After all that's the important bit right?
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According to the Coticule.be site - which is where I got the angle calculator from, the optimum angle is between 17 and 18 degrees but a range of 16 to 20 is OK, Once you get below 16, the bevel is being elongated and becomes too thin at the very edge to maintain integrity. Using tape helps to increase the angle so that the edge has enough steel behind it to be usable. Going above 20 degrees and you get a very small bevel that will require setting more often.

All good fun, isn't it.
 
Good fun indeed. My expertise really lie in knifemaking, specifically high end kitchen knives where the optimum bevel angle is 15-18 degrees per side, so not that different really.

In both cases, how thin the the blade is behind the edge is extremely important too. In other words, how thin the blade is ground before the bevel is set. That's maybe drifting off topic though....
 
Hi folks, sorry, dragged away by more important things yesterday (as if there's anything more important than honing our razors!)

Anyway, I hope I can summarize my thoughts as follows...

* Tape: Keeps the bevel narrow and prevents wear on the spine and so keeps it looking better, but it steepens the bevel angle over time. The steepening probably won't make any appreciable difference over a few decades, especially not if you keep your razors in good condition and rarely need to reset bevels.

*No tape: Leads to wear on the spine and a increasing bevel width, but maintains the bevel angle over the long term. A worn spine and a wide bevel make no functional difference to the razor.

So it really comes down to which you prefer - keeping the bevel angle constant over the very long term at the expense of the razor not looking so nice, or preventing spine wear and a widening bevel at the expense of the angle steepening over time.

There's no right or wrong, just personal preference, and mine is based on my hope that my new razors will still be shaving at the perfect angle for their owners in another century or more - just as my granddad's oldest razors are still doing for me now.

Anyway, whichever camp people are in, at least those who express incredulity that there can be people in the other camp should hopefully understand why ;)

Cheers,
Alan
 
A well presented set of information. Based on this, I shall tape the spine and hone away to my heart's content knowing that I shall probably be too old and decrepid to care by the timr it is worn out! Thanks guys as always.
 
mikew said:
Good fun indeed. My expertise really lie in knifemaking, specifically high end kitchen knives where the optimum bevel angle is 15-18 degrees per side, so not that different really.

In both cases, how thin the the blade is behind the edge is extremely important too. In other words, how thin the blade is ground before the bevel is set. That's maybe drifting off topic though....
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I don't think that's off topic - it's very relevant when you compare say, a Filarmonica to a near wedge. The Filarmonicas are known to have tiny bevels becaus of the extremely hollow grind. You could put exactly the same angle bevel on a near wedge and it will be noticeably bigger purely because there's more metal that has to be removed. In fact you can see that in Oscrofts diagram above - ignore the red lines. The pale grey area represents a hollow grind whereas mid grey is much more wedgy. The area of the bevel is where the line from the spine hits the ground blade and is much bigger on the wedge.

Mike I'm not trying to teach grandmother to suck eggs here - it's for the benefit of non straight users who may not have experience of honing and bevel angles etc.
 
UKRob said:
Mike I'm not trying to teach grandmother to suck eggs here - it's for the benefit of non straight users who may not have experience of honing and bevel angles etc.
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No worries mate, happy to suck an egg now and then.
 
Any recommendations for a quality tape to use? Also wondering if you use tape for honing should you also use it for refreshing the edge? Finally would someone mind posting a photo of a razor taped for honing? I'm not sure how far the tape goes onto the blade. Sorry for the multiple questions.
 
I use Scotch 3M super 88 a real good quality tape with great abrasion resistance, cheap tapes tend to leave more behind on your hone, try and get the tape to equally cover both sides but don't worry if it's not quite perfect as long as you have the leading edge of both sides of the spine then every thing will be OK. http://solutions.3m.co.uk/wps/portal/3M/en_GB/ElectricalMkts/ElectricalSupplies/products/electrical-tapes/insulation-tape/scotch-super-88-premium-black-0216mm-pvc/





I also forgot to add to remove the tape residue left on the blade is quite easy, just remove the tape then wrap it around your finger and dab over the blade it removes it instantly without much effort.
 
Absolutely if you want to retain the angle you should always tape, another thing when you use the tape while resetting the bevel you should re-tape the razor before you move on to the next stone because the tape will wear, once you move on to a 5K stone you shouldn't have to re-tape as the next three hones are more about refinement and polishing and hardly wear the tape at all.
 
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