Thread: A Hollow Spine

Originally Posted by Utopian

I still haven't got a clue what is being discussed. Is the hollow, or concave, or swayback, or poor posture...

1) on the top of the spine (meaning directly opposite the edge and when placed down on the flat surface the blade is perpendicular to the surface and the edge is pointing away from the flat surface).

or

2) on both sides of the spine on the areas where hone wear occurs (meaning the blade is parallel to the flat surface).

If #1, then that's just a typical spine for a smiling blade.
If #2, then that can be uneven hone wear.

Click on link OP provided to the wiki. Scroll down to "types of spines" and there is a picture/diagram of exactly what is being referred to as a hollow spine. It is labeled in the diagram as such.

Many of my blades have a slight or full hollow spine as it seems to help guide the smile on the edge by reflecting the curvature. Without this, on subsequent honing a straight spine would result in an inevitable straight edge thus loosing the smile. At least that is what is going on with the ones I have.

One more observation based on an idiotically small sample: If the razor spine is concave, the cutting edge will mirror that concavity, and the razor will lie flat on the hone (if past honing hasn't messed with good geometry).
If you force a smile onto a straight spine the razor will not lie flat on the hone and you will have to use the appropriate stroke to hone, the rolling X or some other name.
Well, that's possibly two observations.
And for a moment of irony: we relish the vintage razor. Often there are the thoughts of the hands that have been on the razor throughout its history. And yet, it is the NOS razor that is paramount. Yes, it was made 'back then,' but no one has put their grubby hands on it, and abused it on the hones.

Hmm, I have one razor that is close to being NOS, that's about it. All my razors are Old and used, the Old ones are still teaching me.

Originally Posted by WW243

One more observation based on an idiotically small sample: If the razor spine is concave, the cutting edge will mirror that concavity, and the razor will lie flat on the hone (if past honing hasn't messed with good geometry).
If you force a smile onto a straight spine the razor will not lie flat on the hone and you will have to use the appropriate stroke to hone, the rolling X or some other name.

If razor with a curved spine and smiling edge is kept flat on a hone, the edge will eventually become straight.
Swooping strokes are used to keep the edge in relation to the spine.

Even as-honing a razor with a straight spine, I always hone 'toward' a smile. This means that the razor is steered away from having a totally straight edge to a small degree and kept out of the dreaded 'frown' condition. JMO

Swooping strokes are used to keep the edge in relation to the spine.

Really Tom, I wish this meant something.

https://www.youtube.com/watch?v=FT3SI8h0GxI

at about 14:39 smoooooooth honing of a Saito.

Originally Posted by WW243

https://www.youtube.com/watch?v=FT3SI8h0GxI

at about 14:39 smoooooooth honing of a Saito.

Hmm. He's only honing 2/3 the bevel length, the heel is untouched and it's a sk2, might as well be straight edge

Sk1 curvature by comparison:

Originally Posted by WW243

One more observation based on an idiotically small sample: If the razor spine is concave, the cutting edge will mirror that concavity, and the razor will lie flat on the hone (if past honing hasn't messed with good geometry).

I don't think that statement holds true Bill. If you take those extreme Japanese Saito Razors, you cannot hone them flat on the hone - a rolling stroke is a must - otherwise you will hone a flat into the bevel. Laying one of those extreme razors on a hone demonstrates that only a part of the edge rests at any point along the bevel.

Edit: Tom beat me to it.

Originally Posted by UKRob

I don't think that statement holds true Bill. If you take those extreme Japanese Saito Razors, you cannot hone them flat on the hone - a rolling stroke is a must - otherwise you will hone a flat into the bevel. Laying one of those extreme razors on a hone demonstrates that only a part of the edge rests at any point along the bevel.

Edit: Tom beat me to it.

Well put.

Originally Posted by UKRob

I don't think that statement holds true Bill. If you take those extreme Japanese Saito Razors, you cannot hone them flat on the hone - a rolling stroke is a must - otherwise you will hone a flat into the bevel. Laying one of those extreme razors on a hone demonstrates that only a part of the edge rests at any point along the bevel.

Edit: Tom beat me to it.

To me, while those razors might be perfectly functional, they are freaks among straight razors. As such, they defy all proven science.