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In praise of good lapping plate

In my history of sharpening and honing (not just razors) I was convinced my Norton lapping stone was adequate to flatten my stones. To my eye my stones were flat and I was good to go on sharpening everything. I took blade to stone happily, but was slightly confused when my supposedly non-smiling blades were acting like a smiling blade on my hone. Undeterred I just honed all my blades with the rolling-X motion, and everything seemed to work out and I was getting pretty decent hones on all my blades.

So, fast forward several months and I finally decided to buy a DMT coarse plate for Christmas. When I got home from holiday it was waiting for me and I was anxious to try it out and see just how flat my stones really were. Well, I spent all last night lapping my three stones (1K/8K and 4K) to flat. Boy, was I surprised but the results of just a few minutes. Turns out every one of my hones were higher in the middle and drastically lower on the edges. I spent several hours on all the stones just to get them back to flat and am hoping I never have to lap them to that extent again.

However, I did learn something in all of this: Flat is relative and can be overcome. In that I mean if you don't have a perfectly flat stone, you can still hone and still get to shave ready. You just have to understand your stone and adjust to what is required. I adjusted to my stone without even realizing what was actually at play. I'm excited to see how my newly flat stones act and feel with my next razor that needs a good honing.
 
Have you ever seen Murray Carter's stones, they look like soup dishes. I do believe having a flat stone is a good idea but I don't think it is possible to make something really sharp without it. I think I may order a DMT course for flattening based on your experience.
 
A one stone progression would be much less critical. The more stones in the progression the more it's working against you. Flat is good.
 
A one stone progression would be much less critical. The more stones in the progression the more it's working against you. Flat is good.
Funny enough, because I was using the same out of flat lapping plate on all my stones, they were all equally out of flat. So each stone acted the same for the most part.
 
Just keep them flat. I don't think an off lapping stone will affect the stones as much as your stroke. Doing the same stroke over and over will wear the stones the same. Which I think is the case here.
 
Just keep them flat. I don't think an off lapping stone will affect the stones as much as your stroke. Doing the same stroke over and over will wear the stones the same. Which I think is the case here.
Agreed. Having a good flat surface is the easiest thing to do. I did struggle initially with getting the entire length of the bevel honed, and now I know why. It was just very surprising as to how out of flat my stones were, and it all stemmed from my out of flat lapping stone. Very interested to see how easy/difficult it will be to hone with an actual flat stone.
 
How do you know that the lapping plate you now have is flat?
How are you able to know that your stones are now flat?
If flat is your goal a straight edge that's truly straight might be a good tool to have.
 
How do you know that the lapping plate you now have is flat?
How are you able to know that your stones are now flat?
If flat is your goal a straight edge that's truly straight might be a good tool to have.
The plate I have is at the very least exponentially closer to flat then my old one. I say this based off of how the lapping went with my new plate. I could see and feel that the sides and corners were lower than the center of my stone as I was lapping. I don't need 100% flat, but anything was better then what I had before, which was so far out of flat it made my straight spine razors act like they were smiling razors when I honed.

I do have straight edges, and I only use them as a guide to rough flat. Nothing is ever truly flat, straight, or level for that matter. There is always going to be some error whether it be from machines or human. And really, to extend your argument, how do I know my straight edge is straight?
 
I absolutely understand your comments and I hope what I wrote is not taken as negative criticism or an argument.
Yes it certainly seems that your stones are now "flatter" given the evidence that you describe, again not an argument or judgement.
I believe that "relatively flat" measurable stone surfaces help my knowledge building while I experiment with different honing techniques.
I think of this as a consistent, repeatable starting point.

My comments centered around my own discoveries with lapping-plates-and how flat they are or aren't. I want my stones to be flat to the extent that I cannot see very much of a strong light under or between the straight edge and the surface of the stone and I want this so as to attempt to remove one of the variables associated with the experiment of honing.

Yes, I agree there is likely to always be some error when measuring any of these planes and "good enough" is in this case in the eye of the experimenter. I was attempting to point in a direction that indicates to you, or anyone else interested, who might desire a working surface that could add some level of consistency to this one variable to our outcomes.
If so a high quality straight edge is a tool I find worth using.
To reiterate it was not my intention to be negative about what you posted, if my comments were interpreted this way I sincerely apologize.

Frank C
 
The plate I have is at the very least exponentially closer to flat then my old one. I say this based off of how the lapping went with my new plate. I could see and feel that the sides and corners were lower than the center of my stone as I was lapping. I don't need 100% flat, but anything was better then what I had before, which was so far out of flat it made my straight spine razors act like they were smiling razors when I honed.

I do have straight edges, and I only use them as a guide to rough flat. Nothing is ever truly flat, straight, or level for that matter. There is always going to be some error whether it be from machines or human. And really, to extend your argument, how do I know my straight edge is straight?
If you bought a straight edge from a reputable manufacturer it will come with a certificate of inspection. It will tell you exactly how straight it is or at bare minimum the maximum deviation from straight. Another good way to ballpark check is to use your lapping plate to flatten two hones then place the two hones with lapped sides together and check the gap between using a feeler gage.
 
If you bought a straight edge from a reputable manufacturer it will come with a certificate of inspection. It will tell you exactly how straight it is or at bare minimum the maximum deviation from straight. Another good way to ballpark check is to use your lapping plate to flatten two hones then place the two hones with lapped sides together and check the gap between using a feeler gage.
Not sure I’d be willing to spend the money for a straight edge just to check my stones...not worth it to me. But to each their own.

Funny enough, that method of placing to flattened planes together to check is used in hand tool wood working as well, and have used it a few times.


To reiterate it was not my intention to be negative about what you posted, if my comments were interpreted this way I sincerely apologize.
No worries. Nothing wrong with a friendly debate, even if it wasn’t suppose to go that way lol. I’ve had discussions like this in wood working forums too about plane sole flatness and how flat you actually need it. Apparently flatness is something that is a hot topic everywhere lol
 
It's been my experience that just about everything about honing "can be" a hot button topic and I hate to think that I may have contributed to this phenomenon. Not my intension!
I really like to experiment and for myself, to get repeatable results that I can learn from I try to eliminate or minimize any variables that I can.
 
Having a hone that is higher in the middle and lower on the edges (side to side), is not necessarily a bad thing. In fact, those who learn the craft/trade of honing in Germany to work for one of the larger Solingen razor factories like Dovo must demonstrate their ability to prepare a hone that has this convex shape. The reasoning behind this shape is that they can be used to hone a razor whose blade is not completely flat. The ridge that goes along the center of the hone will always contact the blade, even if the blade is not straight.

Now, having a hone that is higher on the edges than in the middle (side to side) is obviously not a good thing as portions of the blade will not be honed properly. Also if the hone is dished end to end, middle of the hone lower than the ends, you will never be able to produce a sharp edge on the razor as the hone will tend to round off the apex of the bevel. However, if the hone is convex end to end, that is, the middle of the hone is higher than the ends, you can still hone the razor.

Hones are not perfectly flat, razors are not perfectly straight and flat. Thus, we use a variety of strokes: circles, ax strokes, x-strokes, etc. to make sure all portions of the blade receive the honing required. In some instances, we have to apply non-uniform pressure between the blade and the hone to insure we have a good bevel from one end of the blade to the other.
 
Having a hone that is higher in the middle and lower on the edges (side to side), is not necessarily a bad thing. In fact, those who learn the craft/trade of honing in Germany to work for one of the larger Solingen razor factories like Dovo must demonstrate their ability to prepare a hone that has this convex shape. The reasoning behind this shape is that they can be used to hone a razor whose blade is not completely flat. The ridge that goes along the center of the hone will always contact the blade, even if the blade is not straight.

Now, having a hone that is higher on the edges than in the middle (side to side) is obviously not a good thing as portions of the blade will not be honed properly. Also if the hone is dished end to end, middle of the hone lower than the ends, you will never be able to produce a sharp edge on the razor as the hone will tend to round off the apex of the bevel. However, if the hone is convex end to end, that is, the middle of the hone is higher than the ends, you can still hone the razor.

Hones are not perfectly flat, razors are not perfectly straight and flat. Thus, we use a variety of strokes: circles, ax strokes, x-strokes, etc. to make sure all portions of the blade receive the honing required. In some instances, we have to apply non-uniform pressure between the blade and the hone to insure we have a good bevel from one end of the blade to the other.
Maybe in time but he's just starting. I been around a while and haven't found that I need one like that. Lol.
 
The problem here is that he had NO idea his hones were not flat. For knives this u.s. pretty inconsequential but for razors it could be a Very Bad Thing. An unknown concave surface that isn't the same from hone to hone through a progression would be tough to work around effectively or efficiently. Producing a convex surface intentionally is a whole different ball game.

I would say if you can't afford a straight edge that is certified (not actually that expensive really) then you need to check your own and quantify how far out of flat it is. As an ex-machinist, I'm not a fan of the "look for light" school of thought. You can do this yourself with a smaller straight edge of about 12" length. Purchase or make a reference surface and set the straight edge on a couple feeler gages at either end, then check the relative size of the gap in the middle. You can make a device that can check straight edges with just a piece of steel and some ground or turned O.D. tubing and a drill/tap and some screws. Much easier to make yourself if you have a lathe.
 
Maybe in time but he's just starting. I been around a while and haven't found that I need one like that. Lol.
I have a couple of blades that are slightly warped as assessed by Dr Matt's tap/wobble test. I have learned how to hone them, but it takes some manipulation of the blade to accomplish it on a flat hone that is 2 3/4" wide. One ting I have done is hone on the side of a hone rather than on the flat surface. Most of my hones are 3/4" thick, so by honing on the 3/4" side I can more apply pressure to the areas needed.
 
I would say if you can't afford a straight edge that is certified (not actually that expensive really) then you need to check your own and quantify how far out of flat it is. As an ex-machinist, I'm not a fan of the "look for light" school of thought. You can do this yourself with a smaller straight edge of about 12" length. Purchase or make a reference surface and set the straight edge on a couple feeler gages at either end, then check the relative size of the gap in the middle. You can make a device that can check straight edges with just a piece of steel and some ground or turned O.D. tubing and a drill/tap and some screws. Much easier to make yourself if you have a lathe.
I’m a hand tool wood worker and The method to test a straight edge is completely different. I find a jointed edge of wood, line the edge up straight, draw a line, flip the edge and line it up again, and draw a line. If the lines are identical and don’t deviate, it’s straight. It’s funny to see the point of view of a machinist compared to a wood worker on flat.
 
Again, for making things from steel that NEED to be straight, it's important to quantify. Wood is just a bit more flexible so small errors aren't as crucial. The method for the shopmade device I mentioned above would be very similar to your line setup, but would allow actual precise measurement of the deviation. Straight edges for precision work can be flat to the fractional ten-thousandths or even millionths of an inch level and are normally checked against a granite surface plate with bluing. Deviations are corrected with hand scraping! Most general work doesn't require anywhere near that level of precision though.
 
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