Hand Tools

Subject:
Re: Also, a question about strops

david weaver
the level of sharpness that we're using in this test is something that won't be improved by stropping. Stropping is a complicated thing, though it doesn't have to be made so in process - but as far as where you gain from it.
* softer steels
* natural stones that create a long but delicate wire edge
* lack of edge refinement otherwise

Strop honing can take the place of a finish stone, but I think most people will come to prefer a finish stone.

Brent beach has something about stropping on his page, but it's simplistic and he's comparing low quality abrasives to a sub micron honing film. Honing films are very precise, but they're a complete pain unless you do only the simplest and cleanest sharpening operations (e.g., a brand new woodworker who just sharpens smoothing plane blades and chisels with a pull stroke in a guide).

There is such an unbelievably large world of purpose made and adapted abrasives (pigments, combination abrasive sticks with wax, pastes), etc, that everything needs to be well defined. The green formax stick that claims to be chrome ox is actually quite practical for a shop. Green chrome ox graded half micron powder is much finer, but the practicality over bare leather is little on tools and much on razors if a finish stone comes up short (it's not necessary with a good finish stone and a good true linen and good hanging shell strop).

The topic can get complicated because it depends on the use.

As far as longevity for planing, i don't think stropping adds any. The pictures under the scope show that the edge is removed very quickly due to wear, no matter what the steel is. The exception is if refinement isn't good or if there is wire edge remaining, I'd imagine you can shorten an edge nominally by allowing it to get damaged for the first few strokes.

My pictures and surface judging on this round of testing suggest that good blades that sustain very small damage at the outset will "heal" themselves if the wood is agreeable. Of course, nothing heals, but the defected area if it's not a narrow and deep groove will wear into some uniformity. The edge won't be perfectly straight, but it will become smooth enough so as not to leave a mark on the wood surface.

On a vintage western razor, stropping is essential. Even on a japanese razor. I've seen people mention that stropping dulls an edge, but severing hairs on every razor that I've sharpened is always improved by proper stropping and the ease across the face is greater with stropping. The only exception that I would mention is .09 micron iron oxide. It might be fine enough to leave a very clean edge, but the shave is harsh to me. even 0.5 chromium oxide is improved quite a bit by the strop in hanging hair tests. Whether it's straightening of the edge or what, I don't know. Sometimes the uniformity of an edge will actually look better straight off of the stone under the microscope, but whatever the strop does is an improvement. Some of the straight looking parts of the edge may not be in line with the rest or they may be part foil and weak.

(I'll admit that I never read too much of the blog with the SEM pictures because I'd already been viewing edges under a metallurgical microscope for a while, and grading stones to sell so as to support my own hobby. even a good metallurgical scope won't show you nearly as much, but sometimes the SEM pictures can be so in your face that it's hard to tell what actual effect they have on shaving)

In my opinion, for razoring, having a good linen and leather (real linen, real shell strop that's not too old, or at least broken in butt strip from horse) is an absolute necessity before making any judgments about edge quality. The edges are so acute that substandard leather can damage them, as can substandard harsh linens. Some of the felt and cotton sold to substitute for linen will actually leave visible scratches in an edge and dull it noticeably.

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