Thread: Fun with Verniers calipers and tape

Originally Posted by gssixgun

Now if one of you math whizzes could figure out exactly how much each layer of 3m tape (the most used that I know of) changes the degree of angle on the 3 major sizes of spines, on the most common widths of razors that would be useful information....

That's very easy to do, but I don't see how it is useful. It seems a math trivia to me with no bearing on shaving unless we have some data that correlate the angle with the shaving.

Originally Posted by gugi

That's very easy to do, but I don't see how it is useful. It seems a math trivia to me with no bearing on shaving unless we have some data that correlate the angle with the shaving.

See above, I agree with you, it has no basis on shaving...

Glen how big would you say the range of working angles for shaving could be?

Originally Posted by 0livia

Glen how big would you say the range of working angles for shaving could be?

If you actually go back into the archives there were multiple tests done, I remember from 8-22 degrees were found to be shavable... But I have never had the time nor inclination to test it...

Originally Posted by gssixgun

Now if one of you math whizzes could figure out exactly how much each layer of 3m tape (the most used that I know of) changes the degree of angle on the 3 major sizes of spines, on the most common widths of razors that would be useful information....

Happy to help, HOWEVER, with a great number of caveats. First, I agree with all above posters who mentioned that there's nothing conclusive to be stated about the meaningfulness of the bevel angle, in terms of shaving, at this juncture. Second, we can easily make calculations for, say, a 5/8" razor, but this takes very little into consideration; for example, with each successive honing, that measurement decreases slightly - and we're dealing in the realm of very small numbers where shaving off a few mils of metal will substantively change these calculations to such an extent as to make the calculations I've posted below meaningless. Furthermore, razors are often not completely even along their length -- curves, smiles, etc. change the blade width at various points -- so again the 5/8" basis for calculations becomes not useful. Lastly, the notion of "a layer of electrical tape" isn't especially useful as there is a wide margin of variety of thickness of electrical tapes on the market. Even confining calculations to "3M Electrical Tape" doesn't help, as that company has multiple products matching that description, which vary in thickness from 7 mil to 10 mil, and even up to 30 mil for certain varieties.

All that said, since you asked, here are the actual numbers. These assume that the blades are completely pristine (no metal has ever been shaved off), and that the blade edge is a perfectly straight line. Lastly, I've based this on the most common 3M electrical tape products, which are 7 mil in thickness.

---

5/8" blade: Each layer of 7 mil tape lifts the spine .642 degrees above the hone
(Note: If 10 mil tape is used, the amount becomes .917 degrees, which is a 43% increase -- thus showing why these calculations are not at all useful unless an absolute standard is established for the type of tape used. As 3M manufactures literally dozens of different lines of "electrical tape", this really becomes especially specious.)

6/8" blade: Each layer of 7 mil tape lifts the spine .535 degrees above the hone

7/8" blade: Each layer of 7 mil tape lifts the spine .458 degrees above the hone

If there really is a +/- 3 degrees of error around an ideal angle for a comfortable shave, then even multiple layers of tape should have no ill effect.

- M.

Originally Posted by gssixgun

If you actually go back into the archives there were multiple tests done, I remember from 8-22 degrees were found to be shavable... But I have never had the time nor inclination to test it...

What archive? I don't remember ever seeing anything outside of 15 to 21 for shaving razors

I wonder if the 8 you're referring to is actually 8*2 = 16

Originally Posted by mrgad

Lastly, the notion of "a layer of electrical tape" isn't especially useful

0.3mm, as stated in my initial post, and in the spreadsheet itself.

LOL ok, 8 sounded a bit thin anyway.
What benchmark does the industry set - with DE blades - for the angle?
Usually they max things out and play them safe.

The sheet seems pretty useful in several aspects.
Imagine you wanting to buy a razor for quite a chunk of money.
You could ask for the exact measurements and find out whether the blade was shortened or not.
Apart from having to use verniers calipers (which I hate) I think I'll give it a shot.
At least it does give a clue. Finetuning aside.

Why isn't it possible to give Bart a Rep, btw?
There is no button.

.3mm, as stated in my initial post, and in the spreadsheet itself.

Sorry, I was just responding to the question about what the math would be, rather than replying to the calculations in the OP.

But, for the record, mil and mm are different units of measurement. .3mm is the equivalent of 12 mil, and thus almost twice as thick as most of the electrical tape sold in the U.S.

Again, I wasn't criticizing the OP's calculations or methods. I was just giving an answer to the question of how much one layer of tape would increase the angle for a specific blade width.

Cheers,
M.

Every vintage wedge that I have ever seen has wear on the spine.

If +/- 2 degrees doesn't make much difference, then the estimate of: 1 layer of tape = an increase of 1 degree included angle; should be more than accurate enough.