Basic Sharpening Theory vs. Stropping

Alright folks, I don't even know how to search this to see if has been asked. I thought I knew a thing or two about sharpening basic blades (knives) and realize I don't, after getting a razor. I have always subscribed to the thought that you should sharpen into the blade to avoid a wire edge, but stropping seems to go against that even though one is still 'sharpening' at a lesser degree. Can anyone offer some sage advice on why stropping should not be done into the blade or if you were careful enough it could be more effective? Is the wire edge still present although at a lesser degree on a 'finished' blade? (the thread with the microscope images appear to show there is no wire edge).

You strop into the strop and soon you will have no more strop, and a blunt, and round edged razor. Stropping is mainly to final polish and line up the 'teeth' of the razors edge. If you sharpen a knife to it's final edge you should be doing the same action with it on leather as well. Albeit, at not so steep an angle.


Mick

The straight razor is a bit different from every other thing you have learned to sharpen, it can be rather disconcerting to many Knife & Tool guys...

There should be NO wire edge ever formed when sharpening a SR, you do not raise a burr then take it off...

I finally came up with a saying some time back about the difference with SR's

The difference with sharpening a Straight Razor from every other type of tool, is your face, getting things sharp is rather easy, but getting things sharp and smooth enough to drag across your face is a bit of a challenge...

Now Stropping is done after all this to align/tweak/burnish the edge into an even smoother/sharper condition, and is always done spine leading, with the minimum amount of pressure necessary to keep the blade flat and even as it moves across the strop...

As far as stropping goes, I don't think I want to mess around with a system that has been around for hundreds, if not thousands, of years. If it ain't broke.......

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Originally Posted by Chippy

Alright folks, I don't even know how to search this to see if has been asked. I thought I knew a thing or two about sharpening basic blades (knives) and realize I don't, after getting a razor. I have always subscribed to the thought that you should sharpen into the blade to avoid a wire edge, but stropping seems to go against that even though one is still 'sharpening' at a lesser degree. Can anyone offer some sage advice on why stropping should not be done into the blade or if you were careful enough it could be more effective? Is the wire edge still present although at a lesser degree on a 'finished' blade? (the thread with the microscope images appear to show there is no wire edge).

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Two topics -- wire edge/ burr and stropping.

A wire edge is simply too fragile and uneven to shave with.
A micro burr/ wire edge will cut skin and collapse when
cutting whiskers. i.e. it will give you nicks but not shave whiskers
well. Meat cutters do not like then either....

The strop is to a razor as a steel is to a butcher knife.
In use the thin edge bends and begins to fold. A strop
or a steel will align and straighten the thin edge restoring
the edge to its potential.

A canvas + leather strop combo has a couple subtle interactions.
The fiber of the fabric hooks onto small folded hooked bits of
edge and pulls them off or pulls them straight. If it pulls
them off they will soon oxidize and make an ultra fine abrasive
that then polishes and cleans the edge a bit. The leather
side continues this process. It further pulls and aligns the
fine edge and it also work hardens the fine edge. Small problem
bits of burr and steel also get removed by the alternating
front back stropping motion. In part this pulling is reflected
in the draw of a strop. Draw being the pull but as shell/ horsehide
strop owners will tell you there is draw and there is smooth draw.

When sharpening a knife the development of a wire edge is the
clue to switch hones. It is proof that the bevel extends to the
edge. The finished edge should not display a wire edge as it
is too fragile but a couple honing strokes just short of a wire
edge on the last hone stone is where it is at.

One interesting exception might be noted. A friend returned from
New Guinea and remarked that his bush crew prized a bright
blue edge on their brush knives when they got them sharpened.
Now I know that this overheating of the edge results in local
hardening so the edge would last longer into the day. Oddly enough
his name was Files so go figure he expected them to file their
machete.

The name of the process where an edge is refined on leather is burnishing. There are some pics around here somewhere showing the refining of the edge as you strop. IIRC, butch harner posted them, but I can't find them right now...!

I don't think plain leather strops are aggressive enough to leave any kind of noticeable burr on the razor - as long as the spine of the razor stays on the strop of course :)

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Originally Posted by niftyshaving

Two topics -- wire edge/ burr and stropping.

One interesting exception might be noted. A friend returned from
New Guinea and remarked that his bush crew prized a bright
blue edge on their brush knives when they got them sharpened.
Now I know that this overheating of the edge results in local
hardening so the edge would last longer into the day. Oddly enough
his name was Files so go figure he expected them to file their
machete.

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Overheating an edge for any reason will not result in local hardening.
Over heating an edge will soften the temper. Overheating an edge to blue will probably soften the edge just a little to a spring temper. This will result in a blade that may not hold an edge as long, but will be a tougher blade and not chip out as easily. This may be what they wanted.
What were they using to sharpen that they got their blades that hot while sharpening.

Welcome to SRP Chippy. Here is a PDF with a very useful writeup on honing and stropping from a 1961 barber manual in the SRP Wiki. :gl:

I used to strop my knives after sharpening on a stone. Have not done that for a while, don't know why I stopped. Works on a knife just as well as a razor.

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Originally Posted by Hawkeye5

I used to strop my knives after sharpening on a stone. Have not done that for a while, don't know why I stopped. Works on a knife just as well as a razor.

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I made a large strop for a mate of mine for just that purpose. I taught him knifemaking years ago, and now he makes some beautiful knives. Hopefully now he will have an even smoother edge to them.


Mick

Quote:

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Originally Posted by Guarnera

Overheating an edge for any reason will not result in local hardening.
Over heating an edge will soften the temper. Overheating an edge to blue will probably soften the edge just a little to a spring temper. This will result in a blade that may not hold an edge as long, but will be a tougher blade and not chip out as easily. This may be what they wanted.
What were they using to sharpen that they got their blades that hot while sharpening.

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In this case the machete steel was junk by our standards
and the temper nothing like an open razor.. I think they
used a dry grinding wheel with sparks a-flying but I was not
there.... I got the feeling that it was a local air quenched
edge that lasted a day that they liked.

Maybe he's talking about something kinda like case-hardening? I don't know.

Quote:

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Originally Posted by Guarnera

Overheating an edge for any reason will not result in local hardening.
Over heating an edge will soften the temper. Overheating an edge to blue will probably soften the edge just a little to a spring temper. This will result in a blade that may not hold an edge as long, but will be a tougher blade and not chip out as easily. This may be what they wanted.
What were they using to sharpen that they got their blades that hot while sharpening.

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Quote:

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Originally Posted by LawsonStone

Maybe he's talking about something kinda like case-hardening? I don't know.

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Not case hardening....
Just the local brush crew's preference for how
they liked their brush knives sharpened.

But, I have always wondered if a single bevel knife
could be improved by case hardening the flat
side. It might improve a mild steel knife but
a quality high carbon... not so much.