Thread: Absolutely, positively the last word on spine taping

This is what mathematicians do when they're bored. I wouldn't swear in court that there are no mistakes here, but this is my first stab at a theoretical approach to spine taping.

Suppose a razor comes out of the factory with height h[0], grind angle 2*theta[0], and thickness 2*t. Because we always hone it with tape on the spine, t does not change, so the razor is ground away to height h[1] and angle 2*theta[1].

First, we solve for the amount of height that we have ground away over the years:

And here is the equation:

Next, let's assume that the razor leaves the factory with a 14 degree edge, and that it ceases to function as a razor when it hits 20 degrees. So we'll set theta[0] and theta[1] to 7 and 10 respectively. Then we use the known height and angle of the razor when new, to solve for thickness.

Substituting eq.2 into eq.1, we can solve for the amount of height which has been ground away by the time the razor reaches 10 degrees, which is the point at which it is trashed.

Conclusion: for any height razor, if you tape the spine, the razor will become unusable when you have ground away about a third of its height. QED.

I am not a math wiz, but let me see if this helps.

A razor is 5/8" high with a taper of 17 degrees. 3m electrical tape is 3.5 mil.

I think at that point you are only adding less that .001 degrees of tilt to the blade increasing the taper to 17.001 or something like that.

Is that what you are saying?

Edit: After posting your other posts appeared. A 5/8 razor = .625 removing a third of that .3/.625 = .48. .625-.48 = .145 which is equal to taking a 5/8" razor to between a 2/8 and 1/8. I would argue that the razor would be useless at about .25 of loss instead of .3 of loss.

No. I am saying that you are wearing away the edge but not the spine, thus making the angle more obtuse. I am calculating how this will affect the lifespan of the razor. I conclude that you will have to grind away 1/3 of the razor before it's trashed, which will probably take longer than you have left to live. So spine taping probably doesn't affect the longevity of a razor significantly.

So if you rerun the equations with the information that I gave you 3.5 mil thickness for tape, 5/8" blade, and a 17 degree angle. Assuming this is a new DOVO or TI and not flea bay razor. What do you get?

Also what about the variant of how much metal is abraded? How do you account for that over a life span say 50 years?

Originally Posted by Johnny J

No. I am saying that you are wearing away the edge but not the spine, thus making the angle more obtuse. I am calculating how this will affect the lifespan of the razor. I conclude that you will have to grind away 1/3 of the razor before it's trashed, which will probably take longer than you have left to live. So spine taping probably doesn't affect the longevity of a razor significantly.

I agree with your theory but not your conclusion here. The idea is to have the sharpest possible edge and that posability deminishes over time when the spine is taped. Besides - taping the spine is silly anyway. If properly honed you will never notice the difference because the side of the spine will be polished - especially on a new or nearly new razor.

Originally Posted by John Crowley

OUTSTANDING EXPLANATION and absolutely correct. If you tape the spine you will eventually thicken the shaving bevel. Pretty soon you have a nice pocket knife.

John

Originally Posted by John Crowley

I agree with your theory but not your conclusion here. The idea is to have the sharpest possible edge and that posability deminishes over time when the spine is taped. Besides - taping the spine is silly anyway. If properly honed you will never notice the difference because the side of the spine will be polished - especially on a new or nearly new razor.

I gotta ask John, just how much time are you talking here????
Weeks , Months , Years, Decades, Centuries ?????
Inquiring minds would like to know???? I know it's sorta silly to ask of course.....