Thread: Honing "Feel"

Nobody really knows why two very very flat surfaces stick together. Nobody has ever bothered to investigate it in depth I think. There have been several theories that have settled out as most likely. Some say Van der Waals forces, others the atmospheric/pressure thing, others think it's microscopic contaminants such as oil or humidity in the air. Maybe a combination? All I know for a fact is that once two surfaces are flat enough, they can stick together with very significant force. One good example I can give from the machining world is what are known as "gage blocks." These are dimensionally accurate steel, ceramic, or tungsten carbide blocks that have been lapped to super fine and extremely flat surfaces. They are used for inspection and measurement down to .0001" and here's the kicker: you can take two of the blocks when in good condition with no scratches or other blemishes and clean them with acetone and a lint-free cloth so that there is no oil or any type of contaminants on the surfaces and stick them together with a slight twisting motion and they will stick like they're glued. If you try to pull them apart in a straight opposing direction (i.e. no angular motion or twisting) they will hold quite fastly. Some of the old advertising materials for certain brands of the blocks would hang quite a bit of weight from one of the blocks like in the old crazy glue commercials to demonstrate their holding power and hence flatness. When assembling them for measuring they are put together like this - it's called "wringing" and there is a defined amount to add to the length of the block stack for each wrung joint (though it is mostly included in the block's advertised length, so it is compensated automatically), so the surfaces are not considered to make perfect and full contact even though they are as flat and smooth as the dickens. Once there is any surface defect or they aren't nearly perfectly flat anymore they will not wring together properly anymore. I have a set I use for dimensional inspection.

Here's a link to one manufacturer's explanation:

Wringing Gage Blocks

I can give from the machining world is what are known as "gage blocks."

Ah, many thanks, could not find the exact term to what I was refering in the previous post as "calibrating tiles in metrology"

They indeed were what I had in mind when I developped my first explanation. I was told at the time it was due to Van Der Waals forces (ingeneering scholl), it's interesting to know the explanation is not that simple.

Still, I stand by the fact that after much pondering, such may not be what happens in the current case. The main reason behind that being that a dry stone does not suck a razor's edge, AFAIK (or at least, not at the grits I am accustomed to).

Therefore my conclusion that the phenomenon known as "wetting" my be a stronger candidate for the correct explanation.

Fascinating discussion, heartfelt thanks gentlemen

I have to admit I do like the idea of a low pressure being created by perfectly flat surfaces. The same effect would apply (to a lesser degree) to a surface that has some sort of wetting agent between it to compensate for imperfections. The low pressure would then create a suction effect because, in order to seperate the two flat surfaces you would have to overcome the force of the displacement of air between the two surfaces. The whole subject is a bit of a mind warp though.

Capillary action

Take two pieces of glass slides, place a drop of water on one of them and sandwich them together. They will stick together.

Originally Posted by 10Pups

Good theory but not applicable to the situation. Case in point. The same thing happens when lapping a stone. However with the weight ratios you can actually turn things upside down and they still stick together. Your car would fall on it's hood. It's all in the water.

I was more referring to the increase in resistance that you feel when honing on higher grit stones as the bevel smooths out - I don't think this has anything to do with water "suction."

-john

This is one of those situations where the phenomenon is very real, but the explanation can get difficult. We spent months with the help of plenty of experts to solve a "stiction" problem involving flat surfaces at fluids, much like the gage block issue. Namely, exactly what height differences is required (how thick does the fluid film have to be, driven by the differences in the land heights of the two surfaces), to be able to come off normal to the surface with a given force X.
Bharat Bhushan has written some good journal articles explaining the science which are very interesting reads.

Oh, but back to the OP - over the last year of honing I have learned to pay more attention to this "feel". And yes it's there. I had a razor the other night that where when coming down the hone with the entirety of the blade it seemed fine - but when I'd come off during my x stroke you could feel the 1/3 towards the toe was scratchy. Kept going till that was gone. Had I not experienced it for myself I'd have never guessed you could actually feel that.

My technical contribution:

Originally Posted by RoyalCake

Oh, but back to the OP - over the last year of honing I have learned to pay more attention to this "feel". And yes it's there. I had a razor the other night that where when coming down the hone with the entirety of the blade it seemed fine - but when I'd come off during my x stroke you could feel the 1/3 towards the toe was scratchy. Kept going till that was gone. Had I not experienced it for myself I'd have never guessed you could actually feel that.

Exactly what I meant, that's "The Feel". Now I know I'm moving in the right direction, so thanks again for all your contributions, I had no idea it would get so cerebral!

Originally Posted by gssixgun

Both


A hollow grind razor getting "Sucked" down to the stone is a good sign but it is variable with the razor and the hone.. The feel of the steel on the hone however is a great indicator of where you are also at.. I don't mean how the razor moves I mean the actual feel of the bevel, if it feels smoother and smoother and less and less scratchy then you are really getting someplace with your honing

After all the science I read, I still think this is the most simple and practical explanation of all. Thanks Glen!

Not to minimize on the discussion, I always like a good discussion, but all the science need to be measure, verifiable and peer review to know which theory is the most correct.

Double O