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I never knew my hones weren’t flat.

At this point you can dress them by rubbing stones of similar hardness together. This will smooth out the surface. It will also flatten them further in line with the Whitworth three plate lapping method by added another reference plate. Once flat they will stick together enough that the stiction is enough to support the weight of a stone. Be careful not to drop them while performing this magic trick. Been there, done that and have the chip to prove it.

Rubbing out pencil grids is useful to see that your getting the full surface. But you will start rubbing out the grids consistently some time before you are totally flat. You can feel a flat stone starting to do weird things as you lap it. Pushing and pulling as you rub the surfaces together.

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No, most are not flat even ones claiming a certain level of flatness.
Atoma's are pretty good though. I have one that is dead flat and the other is pretty close but not perfect.
Average diamond plates are great for slurrying and cleaning.
 
Forgive my musings in advance!


Flat is nearly a philosophical property! Flat can be viewed as a spherical surface or a combination of several spherical surfaces with radii that limit on infinity. The larger the radii the higher the degree of flatness. Of course any kind of a perceived step would have a very small radius. Any deviation that could be determined with a straight edge would have radii expressed in walkable dimensions. A .001" dish over an 8" hone would have a radius of 1/8 of a mile.

I was reading about some 7 meter telescope mirrors that were ground to a very high accuracy. They said that the accuracy, if enlarged to the size of the U.S, would result in the highest hill being 5/8" high and the deepest valley being 5/8" deep. Grinding each mirror took two years.
 
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I shaved with this Bengal near wedge after a honing on my newly flattened coticule. Great shave, complete bbs. Although I suspect it shaved better couldn’t really tell if it was better today than after a normal honing as the coti has always given a really sweet edge especially when freshly honed but today was a beautiful shave.
 
Flatness is an interesting topic. Achieving, measuring and defining flatness is science within itself. We go around thinking that many common surfaces are perfectly flat. When you look closer you realize that flatness is much less common than you thought. Most things you assumed were flat aren’t even close.

Some industries demand high levels of flatness for measurements. They go to extreme measures to get flat surfaces to measure from.

Here’s the catch. Even if you managed to achieve a perfectly flat surface, it will only stay that way under absolutely perfect conditions which again are virtually impossible to achieve. Things move and change shape. Take a perfectly flat slab off its mounting table and support it at different points. Not flat anymore due to a different deflection pattern. Take a perfectly flat slab and heat or cool one side even a little. Not flat anymore due to differential thermal expansion. Take a perfectly flat slab and scratch or polish it. Not flat any more due to physical damage.

These aren’t just theoretical problems. They can be measured and they seriously throw off the precise measurements that surface plates are used for. Perfect flatness is a pipe dream. We can get closer and closer but never quite achieve it. It’s a classic example of diminishing returns as the above example of a two year grind for telescope mirror demonstrates so beautifully. I can just imagine the well meaning worker that gave the mirror a final polish on his jeans before packing it up.

Funnily enough, even today, it’s Stone Age tools that offer the highest level of precision. The very best surface plates and straight edges are made of granite. Granite has several properties that give it advantages over other potential materials. Granite has a very low coefficient of thermal expansion. Much lower that steel, glass or acrylic. It’s remarkably stable with changes in temperature. Granite has a low Young’s Modulus and deflects little under it’s own weight. To further reduce deflection the slabs are always thick compared to their span. Proper surface plates will have exact instructions on where to support them. Care must be taken to ensure that each support is taking the correct amount of weight. Granite is extremely hard and so resistant to wear and damage. And finally when granite fails it does so by chipping rather than denting. If you ding a metal plate you get both a low spot and a high spot. Granite will only have a low spot which means that instruments still sit flat on the surface and don’t wobble.

So far @Jakebullet has been blissfully unaware that his sones weren’t flat. Now he will have to accept that they never will be. The good news is that it doesn’t really matter. In practice close enough really is good enough. My granite surface plate, Atoma diamond plate and Whitworth lapping methods get me flat enough to develop an edge that gives a perfect shave. At the end of the day it’s the shave result that matters.
 
Some brilliant responses!
I never knew flatness was such a huge and interesting subject.
I think for my own uses I’ll stick with the probably not flat diamond plate for now and shave test razors from the rest of my stones I’ve just lapped on it. The flattened coticule shave was great today and I’ll try a razor honed on the flattened jnat tomorrow. The Welsh slates the next couple of days.
I’ll buy a decent straight edge too as I was using the side on lapping plate as a straight edge to gauge the stones but now I hear that even that may not be straight.
I was indeed blissfully unaware of my problems and the problem of flatness as a whole. I’m glad I’ve come out of my cave but the light sure is blinding.
 
Flatness is an interesting topic. Achieving, measuring and defining flatness is science within itself. We go around thinking that many common surfaces are perfectly flat. When you look closer you realize that flatness is much less common than you thought. Most things you assumed were flat aren’t even close.

Some industries demand high levels of flatness for measurements. They go to extreme measures to get flat surfaces to measure from.

Here’s the catch. Even if you managed to achieve a perfectly flat surface, it will only stay that way under absolutely perfect conditions which again are virtually impossible to achieve. Things move and change shape. Take a perfectly flat slab off its mounting table and support it at different points. Not flat anymore due to a different deflection pattern. Take a perfectly flat slab and heat or cool one side even a little. Not flat anymore due to differential thermal expansion. Take a perfectly flat slab and scratch or polish it. Not flat any more due to physical damage.

These aren’t just theoretical problems. They can be measured and they seriously throw off the precise measurements that surface plates are used for. Perfect flatness is a pipe dream. We can get closer and closer but never quite achieve it. It’s a classic example of diminishing returns as the above example of a two year grind for telescope mirror demonstrates so beautifully. I can just imagine the well meaning worker that gave the mirror a final polish on his jeans before packing it up.

Funnily enough, even today, it’s Stone Age tools that offer the highest level of precision. The very best surface plates and straight edges are made of granite. Granite has several properties that give it advantages over other potential materials. Granite has a very low coefficient of thermal expansion. Much lower that steel, glass or acrylic. It’s remarkably stable with changes in temperature. Granite has a low Young’s Modulus and deflects little under it’s own weight. To further reduce deflection the slabs are always thick compared to their span. Proper surface plates will have exact instructions on where to support them. Care must be taken to ensure that each support is taking the correct amount of weight. Granite is extremely hard and so resistant to wear and damage. And finally when granite fails it does so by chipping rather than denting. If you ding a metal plate you get both a low spot and a high spot. Granite will only have a low spot which means that instruments still sit flat on the surface and don’t wobble.

So far @Jakebullet has been blissfully unaware that his sones weren’t flat. Now he will have to accept that they never will be. The good news is that it doesn’t really matter. In practice close enough really is good enough. My granite surface plate, Atoma diamond plate and Whitworth lapping methods get me flat enough to develop an edge that gives a perfect shave. At the end of the day it’s the shave result that matters.
Very well said!
 
Stones just need to be flat enough. If I can hold a straight edge to a stone and not have huge chunks of light coming through from the other side, that's good enough for me. I bought a brand new 11.5 inch Hard Black Ark from Dans a while ago and it is very slightly dished down the long axis, maybe a drop of 1 or 2 thou in the center tapering evenly to the ends, ain't gonna bother lapping it, that kind of deviation isn't going to show up in honing in my experience. Softer waterstones are about the only stone I lap on a regular basis but I don't tend to use them much these days. There is a good thread over at another prominent shaving forum with some pics of Transluscent Arks that were used in the razor trade in Germany over decades and decades and they were dished beyond belief, yet they still used them in that state and turned out razors that weren't exactly slouches in the cutting department.
 
If you get a diamond plate from a reputable manufacturer it will be plenty flat enough to suit your purposes. Cheap import plates I would check before relying on their flatness. A finishing stone worn to a concave surface will only help you get edge contact faster, the only bad part about that is if going back to a flat stone it will take you a little longer to get to the apex. Simple to solve with a bevel set. What you don't want if you value your time is to use a series of stones/hones in a progression that are all at differing levels of flat. If going from a 5k concave honing surface to an 8k flat honing surface for instance, might take you a while to get to the apex.
 

timwcic

"Look what I found"
Chasing flat is like chasing a edge, I will drive you crazy getting there. I get happy results using granite countertop drop dumpster diving at the local fabrication shop. Do all my lapping outdoors. Can handle full sheets of W/D easily. Diamond plates go on a silicone mat. I use smaller drops for SIC powder and trash them when they wallow. Hose all down when down. As long as a quality straight edge shows no light checking the standard eight travels, I am good to go

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I honed my Henckels Friodur 17 1/2 on 8k lapping film, 12k lapping film, then the newly flattened jnat with milky slurry and shaved with it this morning Is it the new flatness? I don’t know but today was a particularly great shave. Tomorrow is the turn of the small piece of Welsh slate which had surprised me by how flat it wasn’t and how easy to flatten it wasn’t.
 
First, flat is critical on a new or unknow provenance stone, because if there are valleys on the stone face that have never been smoothed, as the stone wears that surface will not be as smooth as the flattened surface and can trash an edge.

So, first flatten the entire stone face. I use a 140-grit plate to quickly lap flat, a CNTG, $30 plate and a Atoma 140, then refine with a 400 & 600 Atoma. Once flat, (multiple pencil grids, 3-5X) refining to a higher grit surface goes quickly. I use the CNTG plate to hog of material and save the Atoma wear.

Lap under running water, and do not use pressure or you will rip the diamonds from the substrate. Some of my Diamond plates are well over 10 years old and see daily use. The CNTG diamond plate is a great value, though not as flat as Atoma.

It does not matter that a diamond plate is dead flat, it will ride on the high spots. A flatter plate is more efficient, and no diamond plate is dead flat, maybe just, flatter. Neither is a Granite Surface Plate flat, unless flattened and calibrated. If you are lapping on Granite, it is not flat, but flat enough.

I resurface before honing to refresh the stone face, remove swarf and keep the face flattish and most important, smooth.

Hard natural stone should be flattened on Silicone Carbide on a steel cookie sheet on a flat surface. Hard stones, (Novaculites) will trash a diamond plate quickly.

Flat is more efficient because more of the stone is making contact with steel, but dead flat is not critical once the stone face has been flattened and smoothed. After the first lap on the stone with a razor the stone face is no-longer dead flat, if it ever was.
 
If you are using film, get a glass tile, from a big box store. I buy 3X12X 3/8 in tiles, then lap them flat on 220 grit W&D, on a steel cookie sheet. Contrary to popular opinion, glass is not flat, close but not dead flat, fortunately it laps flat easily on 220 paper.

It will leave a nice satin finish, that will hold film like glue. Use known grit film to “grit rate” your slates. Stria is finer or not.
 
I took a Gold dollar, took it back to 8k film, then 12k film then honed on on the newly flattened smaller Welsh slate under plain running water until it stuck fast to the stone all along the edge. It cas cutting hanging hair perfectly and I shaved with it this morning.
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It gave me a brilliant smooth shave. But then I thought, I should’ve shaved first off the 12k film to compare what difference the slate made to the feel. So this morning I took a shuredge 5/8th to an 8k then 12k film and shaved off that. While it was very sharp and gave a fine shave it lacked the softness of the slate. Last one to try is my newly lapped big chunk of supposedly 15k Welsh slate which was the least flat of all.
 
The last of my stones I lapped was the 8x3 chunk of Welsh slate. Much darker when wet than it’s little cousin and labelled at 15k by the seller. Id honed up my 5/8ths Shuredge to 1 micron lapping film and done a test shave. So today I took that razor to the newly flattened Welsh slate.
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This was my final stone I lapped, the hardest and least flat of all my stones and the one that made me aware of the issue in the first place.

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I use it under running water until the blade sticks to the stone, then I stop.
Last time I honed on it it took about 200 laps, much longer than my other Welsh slate and my coti which usually grip around 30.
Today it started gripping around 20 laps and at 30 the blade wouldn’t move at all in either direction. This stone has never gripped a razor so tightly, in fact, no stone I’ve owned has gripped the razor quite like it.
I stropped then tried an HHT and was surprised by how consistently and easily it cut the hair. Often I have to fiddle with it slightly but not today.
Im very interested to see how this freshly stoned razor shaves tomorrow.
 
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Shaved with the big lapped slate edge this morning.
I had high hopes for this edge as the honing had gone well I felt.
I wasn’t disappointed, this is by miles the best shave I’ve had from this stone. Post shave feel is excellent, soft, smooth crazy close and one of the best shaves I’ve had in ages.
I saw a video of an American guy on YouTube who’d bought one these stones and said he would only use it for a doorstop. I don’t know what stone he got but mine is brilliant.
I couldn’t really tell the difference before and after with my coti and smaller slate, but they were mostly pretty flat anyway, but I feel a big improvement with this one and I’ll be using it more.
 
I wasn’t disappointed, this is by miles the best shave I’ve had from this stone. Post shave feel is excellent, soft, smooth crazy close and one of the best shaves I’ve had in ages.


this is a great feeling. i dont think a lot of people who dont appreciate honing get this.

Its an amazing feeling in so many ways. Its like a commercial for a crazy cold beer after a crazy hot, tiring and exhausting day. You thank the hops, the brewer, the brewing equipment, the bottle maker, and yourself for choosing that bottle as it all comes together and dayumn that was good beer… i mean shave, as you look at the tang stamp, the grind, the scales, the edge and the stone and yeah… that’ll do pig, that’ll do.
 
this is a great feeling. i dont think a lot of people who dont appreciate honing get this.

Its an amazing feeling in so many ways. Its like a commercial for a crazy cold beer after a crazy hot, tiring and exhausting day. You thank the hops, the brewer, the brewing equipment, the bottle maker, and yourself for choosing that bottle as it all comes together and dayumn that was good beer… i mean shave, as you look at the tang stamp, the grind, the scales, the edge and the stone and yeah… that’ll do pig, that’ll do.
Hahah it’s very true and a fine feeling to put a great shaving sharp edge on a piece of metal from a chunk of ancient stone, it’s a caveman moment and one only appreciated by a few. @Slash McCoy once told me that when it happens to him it’s all he can do to stop himself from spiking the razor triumphantly onto the bathroom floor touchdown style.
 
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