Thread: Rockwell hardness and honing

Discussion topic ... not a lesson from me.

The recent thread "Swaty Stones for finishing" got me
pondering about why we want to use a light touch for honing
and how it is possible for such a variety of hones from
Arkansas to Waterstones all qualify as razor hones.

In the method for measuring hardness a hard object
either a hardened ball, or a tungsten carbide or diamond
probe is pressed into the object being measured. The
amount of pressure used can be large (150 kilogram) and the
resulting depth of penetration of an indenter is measured.

Hardness

For finish honing we want as shallow an indent or scratch as
possible so the multitude of particles that result from a
fine grit combine with a light touch to produce uniform and
shallow abrasions.

Bevel setting is slightly different. We want more aggressive
abrasion so the sharp bits need to be further apart and
bigger to generate larger cuts. Between bevel setting
and finish honing the key is to eliminate the furrows from
the previous hone and maintain the geometry.

A slurry is interesting in that the grit in the slurry tumbles and
generates local very high pressure zones. Pasted strops are the
reverse of slurry in that they do not present their grit
with much authority and thus tend to polish more.

So the key point is that a light touch no mater what the hone
will generate much smaller abrasions and this consistent light
touch is critical for a final finish no mater what hone is used.

All resulting in a strop ready edge.

Discuss, thoughts...

A full hollow razor has a mighty fine edge. Some of the older Solingens are about as thin as tin foil at the edge. I use firm pressure during some of the honing but I think that as we progress less pressure is advisable. The old Sheffield wedges have a bit more metal to support that edge but unless setting a bevel I tend to use light to weight of the blade pressure towards the end. Just what I do, not saying it is "right."

Originally Posted by JimmyHAD

A full hollow razor has a mighty fine edge. Some of the older Solingens are about as thin as tin foil at the edge.
.....snip...

Good point. Full hollow blades distort with pressure and
badly so with uneven pressure. This type of distortion may
also be a reason beginners have more luck with heavy
blades. Not that they inherently shave better but a beginner
with a slightly heavy hand might be able to hone them better and
a sharp blade shaves better. I know that my most common
"sharper than a Feather" honing results are on my heavy blades.

Hmm, I guess I just told myself to lighten up and revisit my Robustos.

Another interesting thing about hardness, or the veriety of hardness between the big regions, England, Germany, and the US. I find US razors tend to have much harder steel vs the ones from England and Germany.

Another interesting issue is stone abration vs hardness. While it may not seem like much, a harder razor wears the stone faster so you need to be aware of the stones flatness. A harder steel will also encourage higher pressures to hone, "Wow this is taking to long, maybe a little extra pressure will fix that!!" Fight that urge It only wears the blade and stones away that much faster...

I tend to agree here with the Chef

IME I find that steels from different regions have different "Honing Combinations" (my term)
Each razor has to go from Bevel set, to Sharpening, to Polishing, to Finishing (if wanted)
How they go through that, is the Combination to that razor, Harder steels IMHO, like the higher grit more, Softer steels like the medium grits more, in general...

Using numbers here a Sheffield might go 20-30-20-20 and be great, where a Friodur might be more like 20-20-30-40 a Filly could be a 20-20-20-20 (numbers used only as illustration)

These combos are not set in stone (pun intended) either, razors from different regions are not all the same, but there are tendencies ...

Originally Posted by gssixgun

I

Using numbers here a Sheffield might go 20-30-20-20 and be great, where a Friodur might be more like 20-20-30-40 a Filly could be a 20-20-20-20 (numbers used only as illustration)

These combos are not set in stone (pun intended) either, razors from different regions are not all the same, but there are tendencies ...

Forgive my ignorance Glen but what do these numbers refer to?

Laps

56789

Originally Posted by gssixgun

Laps

56789

Laps on different grits? the same grit?

Each number, if I am correct, is referring to the amount of laps that particular razor may need on the basic hone Grits Glenn Mentioned. For example my Henckles may need: 20 (1k), 20, (4K), 30 (8K), and then 10 (12K).

Natural hones are of course rock and for the most part are way harder than any razor steel. The scale for hardness in steel is totally different than the one for classifying hardness in a rock. However even if you use a material way softer eventually it will wear away the harder one. Think a diamond stylus and a soft vinyl record.