S-Grinds

[cotedupy]

[I'm sure this has been talked about before, but I don't know the correct terminology, so it makes it a little difficult to search for it.]


I was sanding / polishing a razor today and noticed something which I have on a couple of other razors, and have seen lots of pictures of, but this has it quite prominently and you can see very clearly in the way the face of it reflects light:

And after:

In knife terms we call this an 'S-grind'; where the blade narrows, then widens, then narrows again for the bevel and edge. It's done to improve food release. So I was just wondering: Does this type of grind have a purpose on a razor...?

And as a special bonus question: What does 'Treble Extra Steel' on this one mean? Is it an early example of nonsense marketing jargon? Or perhaps to do with the temper, like 'Doble Temple' Filis? Or something else entirely?

TY!

 

[Darth Scandalous]

Does this type of grind have a purpose on a razor...?

It's usually called a belly, or sometimes a horizontal stabilizer. In theory it mitigates some of the flex in the blade while shaving, while still being a very light blade. Many razors were ground that way. Filis notably were not. @Matt O has some big reground Sheffields that are very thin with no appreciable belly. If you go to the Koraat website you can see a variety of examples of bellied grinds, from very thin to fairly pronounced.

Here's a photo I took of a Koraat (left) and a Fili EPBD (right).

 

[JPO]

Belly hollow gound blades are probably my favourite type of grind. As mentioned, this adds a little support to a flexible grind. Some extra hollow ground blades really benefit from this belly. It works best if there is a stabilizer near the heel.
The blade needs to be thin behind the belly for it to have any effect. So if you have not noticed anything different, that is probably the reason.
Most of the full hollow razors from Ralf Aust have a belly.

 

[cotedupy]

It's usually called a belly, or sometimes a horizontal stabilizer. In theory it mitigates some of the flex in the blade while shaving, while still being a very light blade. Many razors were ground that way. Filis notably were not. @Matt O has some big reground Sheffields that are very thin with no appreciable belly. If you go to the Koraat website you can see a variety of examples of bellied grinds, from very thin to fairly pronounced.

Here's a photo I took of a Koraat (left) and a Fili EPBD (right).
View attachment 1557010

Ah cheers, makes sense.

Another one then where the kitchen knife world uses the same term to mean something completely different - a knife with a pronounced ‘belly’ would be akin to a ‘smiley’ razor.

(The particularly confusing example of this is ‘bevel’... The bevel of a razor is the ‘edge’ of a knife. Whereas the ‘bevel’ of a knife doesn’t really exist on a razor, it’s kinda where the hollow ground bit is.)

 

[cotedupy]

So who can explain ‘Treble Extra Steel’ now for me?

I’m guessing it means my razor is at least 50% better than a DT14...

 

[JPO]

The bevel of a razor is the ‘edge’ of a knife.

I my world the bevel of a razor is from the end of the hone wear on the spine to the apex. It is one plane, and one bevel, with something missing in the middle. It is also the reason I don't think you can cut in a new bevel without honing the whole bevel plane, including the part on the spine.
If you protect the spine with tape afterwards it is different.

 

[DrStrange]

Korn patented his own variety of belly grind.

https://patentimages.storage.googleapis.com/74/85/7b/b95094ff7a146a/US693524-drawings-page-1.png

US693524A - Razor. - Google Patents