Thread: Fun with Verniers calipers and tape

Originally Posted by hoglahoo

I agree! Robin, could you check on that for us?
[...]
Thanks buddy

Incidentally, he recommends 3 layers of tape to produce the final cutting bevel. So the final angle would be approximately 17 degrees.

Originally Posted by 0livia

Now is there a way to adjust the spreadsheet to german tape thickness?

Just replace .3 in G4-J7 with the desired thickness.

Here's a bit of background, taken from Schmidt, Max: Das Rasiermesser, sein Werdegang, seine Pflege, Radebeul, 1939, via Bayerische Staatsbibliothek (full text here: Digitale Bibliothek - Münchener Digitalisierungszentrum, thanks mh!). So we are looking at 15°.

Having done a bit more research, I am pleased to announce that I have found a solution to our problem, at least as far as sharpness is concerned: Sharpness testing machine - Patent 4178797. Now, we just need to build this thing. Failing that, we should do a little fundraiser and rent a Sharpness tester.

15° seems very rare in my fundus.

Originally Posted by 0livia

15° seems very rare in my fundus.

A moderator of a German forum kindly contributed measurements of 20 new razors. The edge angles are all between 15° and 20°, the majority being around 17°.

He also added that the main problem with old razors is honewear caused by bad honing, i.e. too much pressure on the spine, thus making the edge angle too steep unless you counteract the narrow spine with tape.

Another comment: Modern razors come with barely visible edges, caused by the production process, in which the edge is put on the razor without the spine touching the hone. Therefore, taping the razor is called for, although the results from the spreadsheet would suggest otherwise.

17 to 18° over here rather.
Old ones. Even the ones with heavy hone wear have more than 17°
That won't make the angle steeper.
Must admit that I don't have verniers calipers, so its not 100% accurate.

The bevel being very narrow can happen to an older blade with a spine down flat as well btw. Here's one. I've honed it some more after having taken those pics and still got only 0.3 millimeter at max. I'd recommend not to hone it taped though. The new owner also wanted it like that.
As far as the new ones - I'd say they are not much worth when not honed by hand.

Usually I look at the razors and then decide what to do.
Amazingly enough its almost the same then what the spreadsheet suggests.

I have no calipers, but I can measure the spines and the widths to within 1/64" using a ruler, which translates to about 0.5degree error in the angle so that's what I did.

I used several vintage razors which have virtually zero hone wear and they have not been reground, and the angles were
18.5 old sheffield wedge
19.0 old sheffield wedge
12.5 wostenholm 'celebrated hollow ground'
15.0 Thiers-Issard hollow ground
20.0 Thiers-Issard frameback
20.5 W&B frameback
16.5 Dovo "Diamond Steel"
15.5 SRD

If 17 degrees is optimal, clearly the first two and the framebacks cannot be made to shave 'optimally' by adding tape to the spine or honing with spine lifted (which only increases the angle).

The one with 12.5 degree angle is not a fluke, I have two of them, which are exactly the same razor, although with sligthtly different markings for different markets.

And all these are large companies, so they pretty much set the standards.

So, as far as I'm concerned the razor manufacturers didn't consider 17 as some sort of a magical number.

Again, unless somebody runs a test that demonstrates that razors shave better with a 17 degree bevel compared to 14 degree or 20 degree bevel, all this is just useless trivia that should have no bearing on how a razor must be honed.

//irony on
Something relatively simple made way too complicated. You don't need a vernier, dial, or digital caliper to math out how much tape to put on a spine... Once someone figures out what the perfect bevel angle is:

• just get one of these dial protractors and avoid the math entirely.

//irony off

The "perfect" bevel for a razor is the same as the perfect angle for any other knife: too many variables for one answer.

Best bevel angle?