Thread: How did barbers hone a wedge in the olden days?

Actually no it really isn't, and perhaps that is the issue...

They could still be way off end to end or side to side..

"The two surface will mate" this is everywhere "But they won't be flat"

I am thinking of an actual protocol that will test it a bit better then simply mating two surfaces together and for now I am done arguing it...

You think that all the info out there is incorrect so be it,, I will be the first to say it if I find you to be correct

Originally Posted by gssixgun

They could still be way off end to end or side to side..

That's why you use the DMTs in steps (2) and (5) you'll find if they're flat or not. That is the protocol you need.

Number 1, the test outlined in post 116 isn't really a test of flatness at all. It's a test of whether the stones are of the same surface contour as the diamond plate. Number 2, if you truly think your diamond plates are flat, try lapping a stone with one, then draw another pencil grid and lap again with a different diamond plate. They won't be the same, and this will show up better on a hard stone where one swipe of the plate doesn't remove enough stone to cover up the difference. A better and more revealing test would be to use your 2 test stones to hone 10 razors apiece and then try to rub them together to obtain flatness. Then check with a straightedge. You will see pretty quickly that they will fail the test. And that's nothing compared to if someone was rubbing two stones together long term for months worth of razor honing.

Glenn, a good test that's easy is to use a straightedge and 3 feeler gauges of the same thickness under it. If all three aren't tight the surface is not flat. You can determine the amount out of flat by using different thickness feeler gauges to see what the gap is in the middle vs. the ends sitting on a reference pair. Checking across the diagonals and in 3 places along the longitudinal axis will give you a pretty good idea.

Originally Posted by eKretz

Number 1, the test outlined in post 116 isn't really a test of flatness at all. It's a test of whether the stones are of the same surface contour as the diamond plate. Number 2, if you truly think your diamond plates are flat, try lapping a stone with one, then draw another pencil grid and lap again with a different diamond plate. They won't be the same

Why do you think the DMT's deviation from flatness is greater than from another DMT plate?

Lapping hones with a DMT plate is perfectly good for honing razors, as almost anybody here can verify, so this is a perfectly acceptable standard regardless of how much DMT is off from flatness and how much one DMT is off from another.

Originally Posted by eKretz

A better and more revealing test would be to use your 2 test stones to hone 10 razors apiece and then try to rub them together to obtain flatness.

You'd be unpleasantly surprised - this biases the experiment towards ending with a flat surface not a spherical one.

Originally Posted by gugi

That's why you use the DMTs in steps (2) and (5) you'll find if they're flat or not. That is the protocol you need.

Testing for flatness with an abrasive tool that causes flatness seems a bit questionable to me. Testing against a non abrasive flat surface plate or straight edge would be much more objective. Also the closer to flat that you are to start with lessons the problems with the two stone system so showing the deviation from flatness by partially flattening the stones is questionable. Between starting by partially lapping then proving flat by lapping again, it sounds like actually rubbing the stones together could be skipped. The three stone method arrives at three flat surfaces that prove themselves against each other without any outside reference

Originally Posted by bluesman7

The three stone method arrives at three flat surfaces that prove themselves against each other without any outside reference.

Yes, and the Earth is flat or round, and it moves with reference to the Sun or vice versa?

Any intro college level course in differential geometry should give you sufficient skills to prove that you need three surfaces to verify flatness by matching. I am pretty sure I pointed that out many posts back.

The exact same thing that makes the hones when rubbed together 'smooth' is what makes them 'flat'. The only difference between the two is quantitative length scale and not qualitative.


For a meaningful argument one must know the relevant quantities and their meaning. For example perfectly flat surfaces do not exist in the real world - at Å length scales you only have the probability of interacting with a quantum electronic state and those probabilities are anything but flat (both spatially and temporally).

So, unless somebody is interested in discussing quantum mechanics and differential geometry on current research level, let's stay confined to the level of practicality.
We are talking about hones that are flat for the purpose of honing razors. Lapping them on DMT 325 is perfectly good for this purpose, so that is a good benchmark to test against. If you want to argue that that's not flat enough and you'll get better edges from flatter hones, start a separate thread where this can be explored on its own merit.

Originally Posted by bluesman7

Also the closer to flat that you are to start with lessons the problems with the two stone system so showing the deviation from flatness by partially flattening the stones is questionable. Between starting by partially lapping then proving flat by lapping again, it sounds like actually rubbing the stones together could be skipped.

You seem to be forgetting the problem. It is to prove that two hones can be made flat by simply rubbing them together without using a third one. You're among the ones who insist it can not be done and that there is an instability towards curved surface.
If you're right you'll always end up with a curved surface (the phase space of those is infinitely larger than the phase space of the flat surface which is even metastable) and a single example of ending up with a flat surface would be sufficient to disprove your assertion.

Originally Posted by gugi

Yes, and the Earth is flat or round, and it moves with reference to the Sun or vice versa?

Any intro college level course in differential geometry should give you sufficient skills to prove that you need three surfaces to verify flatness by matching. I am pretty sure I pointed that out many posts back.

The exact same thing that makes the hones when rubbed together 'smooth' is what makes them 'flat'. The only difference between the two is quantitative length scale and not qualitative.


For a meaningful argument one must know the relevant quantities and their meaning. For example perfectly flat surfaces do not exist in the real world - at Å length scales you only have the probability of interacting with a quantum electronic state and those probabilities are anything but flat (both spatially and temporally).

So, unless somebody is interested in discussing quantum mechanics and differential geometry on current research level, let's stay confined to the level of practicality.
We are talking about hones that are flat for the purpose of honing razors. Lapping them on DMT 325 is perfectly good for this purpose, so that is a good benchmark to test against. If you want to argue that that's not flat enough and you'll get better edges from flatter hones, start a separate thread where this can be explored on its own merit.

I'm arguing that using a DMT for testing biases everything towards flatness. It's also a given that with a flat reference and time one can make a flat surface on one stone and anything with which to abrade the stone. Your saying that rubbing two stones together will result in flat stones and you mathematically proved it. So you should be able to do this without a reference.

Originally Posted by bluesman7

I'm arguing that using a DMT for testing biases everything towards flatness. It's also a given that with a flat reference and time one can make a flat surface on one stone and anything with which to abrade the stone. Your saying that rubbing two stones together will result in flat stones and you mathematically proved it. So you should be able to do this without a reference.

Nope that's not how the correct logic goes.
1) Mathematically it's easy to prove that rubbing two hones together results in flat surface
2) Some people do not understand the math or don't believe it represents the problem correctly but can not offer anything better
3) People in (2) do believe that matching against a 'reference' is good enough as a proof
4) Use the method that is supposed to not work to produce surfaces that are not supposed to be achievable and prove that they have been achieved through the matching against a reference, which is accepted proof even for the math unbelievers

Do you need a Venn diagram that illustrates how the few strokes over the DMT are the bridge that allows people to glimpse into a world they do not think exists?

Yes the DMT is abrasive and it is possible that the curvature is so small that the DMT erases it before it can reveal its existence, but if the curvature is so small, then it clearly is not relevant and for purposes of honing razors the hones are flat enough.

I happen to have 2 Choseras 1k and decided to play a little and see what happens.
First set of tests was with the hones as they are , I would do pencil grids to see the topology and then lap against each other. Hone #1 had a hump, hone #2 had a dish along one of the diagonals from knife sharpening. I lapped them together for a bit then did new pencil grids and lapped just a little on used DMT to see how the topology changed. Did not see much difference so I did more sets of lapping and checks. It started to look like the two were getting lapped similar, so I thought they will become true eventually. But that would take a ton of time and is not at all rational use of one's time. After talking with Glen, I got to test more, this time I lapped hone #2 flat and kept hone #1 as it was. After several lapings hone #2 developed a dish similar to hone #1 which did not improve from its original state. Basically what would happen is grit will accumulate between the two hones in the middle and will create a dish. The grit also slows the lapping process considerably. I am not very convinced that 2 hones can lap each other to true flat based on this limited test.

For the 3 hone lapping method, that has been around for a a long time. Dr Naka posted about that after his visit with Iwasaki.

Here is the blog post, he specifically explains that 3 hones are needed to make a true surface and that two hones are not going to lap each other flat.

　Hide's Export　　: Iwasaki and Jnats (part one)

I am a simply man, given to simple solutions that avoid the use of quantitative, repeatable experiments that don't deviate more than 0.0001 percent in any direction. Qualitative interjections of biased belief systems designed to show off the intellectual eruditeness of the writer is cross productive to the simple solution of an X pattern on the hone and rubbed, underwater, with a DMT in a figure eight pattern till the X's disappear should suffice as proof that a direct, unencumbered, approach results in a useful end product, i.e.: a flat hone.

I would also like to point out that the earth is neither flat nor round. Round is a term used to assure the populace that all is alright in the world. The earth is a mis-shapen ovoid fraught with bumps and depressions mostly covered in water. Please don't try to dissuade me, I am adamant in whatever level of truth and reality I am in currently.

And to quote someone (or something), ....and to all a good night (unless you are on the other side of the world at this precise moment then its a good day.)