Norton flattening stone - how flat is flat enough?

[Brassplyer]

I got a Norton flattening stone to try as an alternative to a granite lapping plate and sandpaper, however it's obvious the flattening stone isn't absolutely flat - sighting across the length there's a slight but definitely visible curve - high in the middle and when checking with a steel ruler there's obvious rocking. It looks like the back side is actually flatter than the grooved flattening side.

Are Norton flattening stones just low grade or does it not need to be micrometer flat?

 

[Legion]

I don't have one, but I haven't heard very good things about them. Most of us here use diamond plates.

 

[Christian1212]

Think those are a cheap option that is acceptable flatness for knives

 

[H Brad Boonshaft]

So, dead flat for stones is a moving target. If you were able to get a stone “Dead” flat the minute you honed on it and created some swarf, it is no longer “Dead Flat” because the razor is not perfectly flat.

The good news is a stone does not need to be “Dead Flat” to hone a razor, just flattish.

The flattening stones can flatten a stone, remove a high spot or a valley, but they are slow and messy and yes, the flattening stone will go out of flat.

A diamond plate is a much better, cleaner and faster solution. Lately Atomas have come way down in price about $50 and are almost in the cheap Chinese diamond plate market prices.

I lap my stones before use, during use and after use to clean, so they stay pretty flat, but absolute flatness is not a concern for me.

Up until the late 90’s and the advent of Razor forums, no one was concerned with stone flatness of stones. And folks shave well on just 2 stones, a course one and a fine one, for centuries.

Don’t over think honing, keep it simple and eliminate as many variables as possible.

 

[LJS]

A diamond plate is one of your better options, though, rubbing a series of unflat stones together actually can result in a flat stone as odd as that may sound.

 

[psfred]

You have to flatten the flattening stones too.....

I just use loose SiC and a chunk of sandstone and check for flatness on my King 300 Deluxe, and use that to flatten everything else. Fine stones get the DMT treatment, but it's only 325 grit so I use the King for lower grit stones.

 

[Brassplyer]

You have to flatten the flattening stones too.....

I just use loose SiC and a chunk of sandstone and check for flatness on my King 300 Deluxe, and use that to flatten everything else. Fine stones get the DMT treatment, but it's only 325 grit so I use the King for lower grit stones.

What is SIC?

How do you know the King 300 is flat?

Since my original post I realized I can get the Norton flattening stone a lot flatter using a large flat file under running water. The file's surface shows to be really flat going by the edge of a steel ruler from a combination square holding it up to a bright light, the same way I've been checking the flattening stone and the honing stones. Definitely got rid of the visible bowing of the flattening stone.

I've determined that the marble lapping plate I have has a visible degree of concavity as viewed using the same steel ruler and light which is reflected in the bowed shape of the stones I worked on with it. Not sure who I could take it to to have that rectified.

 

[H Brad Boonshaft]

SIC is Silicon Carbide.

If you are just flattening stones, go to a big box hardware and buy a 12X12 marble or granite floor tile and a Steel Cookie sheet from a dollar store.

Put the cookie sheet on the tile on the floor, put your loose silicon Carbide powder, 60 grit, or a sheet of Wet and Dry, mark a pencil grid on the stone, lap until the pencil grid is removed.

Mark a new grid and remove it again. The stone is flat when you can completely remove a pencil grid in less than 10 laps. Then move up in grits using wet and dry sandpaper to 220.

Or buy a 140 and 325 grit diamond plate, mark a pencil grid and again, you are flat when you can completely remove a grid in less than 10 laps. Even cheap Chinese diamond plates are flat enough to lap stone to hone razors.

You can have a Granite lapping plate resurfaced and calibrated, but it can be pricy depending on how far out of flat it is and what degree of flatness you want it calibrated to.

Calibrated Granite Surface plates are not intended to be used as lapping surface. It is an absolutely flat surface on which to work to ensure the accuracy of precision measurements taken on top of the plate.

In fact, it is recommended that the plate be covered to prevent dust from landing on it when not in use to prevent excessive wear.

 

[psfred]

Marble tiles are quite flat to start with, but also quite soft and will be dished very quickly if used bare. The steel pan won't wear much, hence the pan on top of the flat marble.

The King Deluxe 300 is a very hard vitrified stone of mixed abrasive, probably SiC and Aluminum oxide. I check it with a straightedge or grid, takes lose SiC grit to flatten it too, or "sharpen" in if the embedded grit gets worn.

 

[natto]

Since my original post I realized I can get the Norton flattening stone a lot flatter using a large flat file under running water. The file's surface shows to be really flat going by the edge of a steel ruler from a combination square holding it up to a bright light, the same way I've been checking the flattening stone and the honing stones. Definitely got rid of the visible bowing of the flattening stone.

You can lap three stones against each other. It takes time and leaves some dirt. Some People used hard red bricks. I used three huge SiC stones for a while, about 4$ each. The idea is to rub #1 on #2. Next is #1 on #3. Then #2 on #1, and so on. Works like a charm. Metal workers use this process to achieve "perfect" flatness. And some loose SiC speeds up the process.

 

[bmiller3230]

I got a Norton flattening stone to try as an alternative to a granite lapping plate and sandpaper, however it's obvious the flattening stone isn't absolutely flat - sighting across the length there's a slight but definitely visible curve - high in the middle and when checking with a steel ruler there's obvious rocking. It looks like the back side is actually flatter than the grooved flattening side.

Are Norton flattening stones just low grade or does it not need to be micrometer flat?

I had one and it was definitely not flat. Consider a diamond plate.

 

[Gamma]

Norton flattening stones, historically, have been not-flat.
Lotta guys used to flatten them. But they wear and then they're not flat.
Most flattening stones are like that, actually. Some better than others. They all wear though. Maybe for sharpening cutlery it's ok. Never made sense to me though.

FWIW, a steel ruler is not always a very good straight edge. The older stainless Alvin rules were pretty good but then they started showing up new with concave ruled edges.

Honing hurdles, or challenges, are often the result of inconsistencies - a sum of variables that fall off the radar easily.
One of my personal honing goals is to reduce, minimize, or eliminate as much of that as possible.

Consistency is a key factor in any honing approach. So I flatten my stones regularly, it's fa fairly simple, easy, and quick practice. The extra 1% of effort has always pais off for me. I lap with diamond plates, and check flatness with a certified straight edge. I really don't see any reason or point to thinking or guessing that something might be flat, or whatever flat-enough is, when knowing for sure it's actually really flat can be done so very easily. It's kind of a no-brainer thing actually.

Establishing and maintaining consistently flat hones was one of the first things that helped me get consistently good edge results. Helping 100s of new users get past that hurdle has proven to be a successful part of their learning process also.

No one ever suffered because their stones were too flat.

 

[Brassplyer]

Norton flattening stones, historically, have been not-flat.
Lotta guys used to flatten them. But they wear and then they're not flat.
Most flattening stones are like that, actually. Some better than others. They all wear though. Maybe for sharpening cutlery it's ok. Never made sense to me though.

FWIW, a steel ruler is not always a very good straight edge. The older stainless Alvin rules were pretty good but then they started showing up new with concave ruled edges.

Honing hurdles, or challenges, are often the result of inconsistencies - a sum of variables that fall off the radar easily.
One of my personal honing goals is to reduce, minimize, or eliminate as much of that as possible.

Consistency is a key factor in any honing approach. So I flatten my stones regularly, it's fa fairly simple, easy, and quick practice. The extra 1% of effort has always pais off for me. I lap with diamond plates, and check flatness with a certified straight edge. I really don't see any reason or point to thinking or guessing that something might be flat, or whatever flat-enough is, when knowing for sure it's actually really flat can be done so very easily. It's kind of a no-brainer thing actually.

Establishing and maintaining consistently flat hones was one of the first things that helped me get consistently good edge results. Helping 100s of new users get past that hurdle has proven to be a successful part of their learning process also.

No one ever suffered because their stones were too flat.

So what did people do before they had diamond lapping plates and readily available straight edges?

Btw since my original post I got an iGaging 24" straight edge, it's supposed to be accurate to +/- 0.0015" over the length of the straight edge.

 

[duke762]

Btw since my original post I got an iGaging 24" straight edge, it's supposed to be accurate to +/- 0.0015" over the length of the straight edge.

That may be a drag to work with due to the length, unless you have really big stones. I made my own (I'm a tool maker by trade), It's even flatter than that, I used all the tricks of my trade to make it as perfect as possible and only limited in accuracy by the measuring instruments I had to work. It's 12 inches long and using a .0001" dial indicator on a granite inspection plate, I had no indicator movement.....I do obsess a bit......flatter is better.

 

[H Brad Boonshaft]

“So what did people do before they had diamond lapping plates and readily available straight edges?”

They really did not worry about it, because it does not matter. Flat-ish is good enough.

Until the internet forums and instant experts no one flattened stone. That is why you find all these old stones that have worn bellies. They work just fine.

Think about it, with a razor you have about a millimeter or two touching the stone at the edge, what difference does the flatness of the rest of the stone make at the edge?

And if you can alter the edge, making a micro bevel the width of a piece of tape and not even have the rest of the 1mm bevel touching the stone, the stone flatness matters even less.

Precision Ground Machinist Flat Stones are ground with a round Diamond Wheel, not a super flat stone or plate. These are 300 grit stones sold in pairs that can produce a mirror finish on steel, they are maintained flattish, by rubbing together.

Now with Water stones we lap them more to clean them, but a razor would just ride on the high spots and unless you are a robot, you are not hitting the exact same high spots with every stroke.

So, the flatness of the diamond plate does not matter all that much nor does the flattens of the stone to a razor. For centuries folks shaved on stones that were never flattened, and I suspect they shaved, just fine.

Nothing wrong with flattening a stone, but obsessing over flatness does not improve an edge. The first lap after the stone was made “perfectly flat” will wear the stone and it is no longer “perfectly flat”.

 

[Darth Scandalous]

Setting aside the question of whether people flattened their stones historically, there are definitely low-tech ways to make a surface reasonably flat. If you look up videos of how files were traditionally hand made, the step prior to cutting the teeth is called "stripping". Basically the blank is set in a bow-shaped jig that allows it to rock and rotate freely while you scrape it. This is quite effective for flattening actually. Same concept is used in watchmaking, I think they call the setup a swing tool. At any rate, using the same concept of a allowing the work piece to rock freely, you can lap a surface quite flat--not machine shop certified flat, but flat enough for most of the purposes we need. I've approximated the process with a stone loosely held in hand and a small hardware store diamond block and it works very well.

 

[Gamma]

So what did people do before they had diamond lapping plates and readily available straight edges?

In one sense it's not so much a matter of 'what did people do before xyz" .
To me it's more like "what did they do before improvements, and how well did it get done?"
That 2nd clause is reaaaallllly important.

Progress is a funny thing. When something is invented we make do with that something and as we go we improve upon what is lacking. We do as best we can with what is available and then we do better when what is available is improved.

Like everything in this world that is related to some sort of technology or science, we've progressed from point A to wherever the path has led us so far. Generally speaking, those improvements lead to a better quality of life. Without a time machine it's impossible to say for sure, but I'd bet a dollar most shaves today are significantly better than most shaves experienced back in the 1850s.

Straight edge rules have been around for a long time. So have lapping plates & similar surfaces. I've seen cast iron lapping plates from the mid 1800s and I am sure older examples exist.
Pyramids were built with a tolerance of 1 mm per meter, which is pretty impressive when you think about it.

Diamond plates like Atomas are relatively new, comparatively speaking, they're a good example of progress making things better. Diamond laps for polishing flat surfaces are nothing new though.
For hones, W/D paper on a truly flat surface works too though.

Way back in history, middle ages maybe, one method of stone flattening involved using 6 stones to lap each other. Home sharpening, and that method of stone flattening was taught in Japanese schools, still is in some places.
The machinists '3 plate method' of creating flat surfaces was developed in the early 1800s.

Thing is, most people didn't own their own razors until the late 1800s/early 1900s. By that time, rulers, straight edges, and squares and such were commonly available.

After ignorance, most razor honing hurdles are born via inconsistency.
Keeping the variables that cause those inconsistencies at bay is relatively easy but it requires discipline.

Keeping stones flat, not contaminating surfaces, maintaining pressure and technique, keeping things simple, etc - all that stuff adds up to the fabled 'last 1%" that separates good from great.
Some people on the internet love to say things like "you don't need to do that".
They might be right, I might not 'need' to do whatever they're talking about.
What they don't understand is that that I choose to do those things because I chose great over good.

 

[Saloogie]

“So what did people do before they had diamond lapping plates and readily available straight edges?”

They really did not worry about it, because it does not matter. Flat-ish is good enough.

Until the internet forums and instant experts no one flattened stone. That is why you find all these old stones that have worn bellies. They work just fine.

Think about it, with a razor you have about a millimeter or two touching the stone at the edge, what difference does the flatness of the rest of the stone make at the edge?

And if you can alter the edge, making a micro bevel the width of a piece of tape and not even have the rest of the 1mm bevel touching the stone, the stone flatness matters even less.

Precision Ground Machinist Flat Stones are ground with a round Diamond Wheel, not a super flat stone or plate. These are 300 grit stones sold in pairs that can produce a mirror finish on steel, they are maintained flattish, by rubbing together.

Now with Water stones we lap them more to clean them, but a razor would just ride on the high spots and unless you are a robot, you are not hitting the exact same high spots with every stroke.

So, the flatness of the diamond plate does not matter all that much nor does the flattens of the stone to a razor. For centuries folks shaved on stones that were never flattened, and I suspect they shaved, just fine.

Nothing wrong with flattening a stone, but obsessing over flatness does not improve an edge. The first lap after the stone was made “perfectly flat” will wear the stone and it is no longer “perfectly flat”.

Thanks for that post.

I couldn't really get my head wrapped around the uber importance guys put on flattening a stone. I get that it's a good thing to have a generally flat sharpening stone, but some guys talk about it like it's science and it's an absolute imperative before honing your razor.

I use a very simple course stone that came in a cheap knife sharpening kit. It's one of these and it works fine, I think, I guess, I hope! It takes the pencil marks off and I think that's good enough. I just make sure I wipe the stone down good after use be used it's pretty gritty.

 

[alex1921]

The Japanese seem to worry a lot about flattening their stones based on all those plates they keep churning out and I doubt most of those expensive ones are used by SR honers.
Also if people shaved so well for centuries how do we explain what happened to SR use after safety razors were introduced? I guess things were not as good as we imagine they were.

 

[Saloogie]

Also if people shaved so well for centuries how do we explain what happened to SR use after safety razors were introduced? I guess things were not as good as we imagine they were.

No, I don't think things were good at all. Honing had to be really difficult. I actually think that why beards were so prevalent in the old days. It was just tough and uncomfortable to shave!