Making flattening stones with 3 bricks

[Winston Chang]

I recently found the excellent sharpening guide by Friedrich Kollenrott, which according to the link from Dieter Schmid is a reference in the German-speaking world. In it, he talks about making "clinkers" (on page 40), which are bricks with very flat surfaces, using three bricks and some abrasive compound. Has anyone here tried doing this?

I've been using a diamond plate for flattening my fine (1000 grit and finer) waterstones, but I don't want to use the diamond plate on coarser stones because it will prematurely wear out the diamond plate. I don't currently have a good way of flattening coarse stones and I'm wondering if using clinkers is good solution because they can be re-flattened against each other.

[Edwin Santos]

Any post mentioning "clinkers" and German can only make me think of Hogan's Heroes.

Back on topic, I've heard many times of people using cinder blocks, or plate glass with lapping grit for flattening coarser stones. Personally, I have used granite countertop remnants with either lapping grit or with wet/dry silicon carbide sandpaper temporarily fixed with spray glue. The sandpaper can be removed in seconds with some lacquer thinner. I think all of these approaches are along the lines of what you are talking about.

BTW, Lee Valley sells abrasive lapping grit in various grits. It's fairly inexpensive. The only issue I kept encountering was that the grit can become embedded in the stone you are flattening and then that piece of embedded grit will leave a deep scratch in whatever you are sharpening. For this reason, I prefer the sandpaper or abrasive film. Like you, I use a diamond plate for fine stones 1000x on up.

[Walter Plummer]

Here is a link that explains how this works. http://ericweinhoffer.com/blog/2017/...-plates-method. There are also videos on YouTube by different machinists on this.

[Tom M King]

I ground telescope mirrors when I was a teenager. I expect that method is taken from making optical flats. I'd say if your time is worth nothing, then have at it, but flats are much harder to make than a parabolic mirror. I still use some of the leftover Carborundum grit from when I was a teenager grinding those optics.

Clinkers here refer to when they used to fire bricks in "clumps" with wood. The closer the bricks were to the fire, the higher the temperature they were fired to. The higher they are fired, the darker they get, and the more they shrink. Clinkers were the black ones that ended up being fired to the highest temperature, and in reduction without oxygen. They are much smaller than the normally fired bricks, solid black, and Very hard. When you throw them in a pile, they make a distinctive clinking sound. Maybe it's different in Germany, and language does change over time too, but that's why they're called clinkers here.

edited to add: Here's what Wiki has to say about clinkers: https://en.wikipedia.org/wiki/Clinker_brick

[Derek Cohen]

I recently found the excellent sharpening guide by Friedrich Kollenrott, which according to the link from Dieter Schmid is a reference in the German-speaking world. In it, he talks about making "clinkers" (on page 40), which are bricks with very flat surfaces, using three bricks and some abrasive compound. Has anyone here tried doing this?

I've been using a diamond plate for flattening my fine (1000 grit and finer) waterstones, but I don't want to use the diamond plate on coarser stones because it will prematurely wear out the diamond plate. I don't currently have a good way of flattening coarse stones and I'm wondering if using clinkers is good solution because they can be re-flattened against each other.

Winston, save your diamond stone for the waterstones by never also using steel on it. Everything wears out eventually. Even my Shapton diamond stone (!). So it lasts you 10 years instead of 20 years ... just buy another. It is cheap in the grand scheme of things. Bricks wear too, and more importantly, they go out-of-flat - and that is a bigger problem than a diamond stone wearing.

Regards from Perth

Derek

[Jim Matthews]

Given the required space for glue in joints, and the seasonal movement of large panels (even veneered ones), isn't this level of precision counterproductive?

I've yet to meet an active woodworker that worries much about "flat" as much as getting solid construction, ready for finish.

My mentor trained as a machinist (at the Advent of CNC) and uses nothing more than a grinding wheel and charged buffer.

His furniture is beautiful and sells at a profit.

[Winston Chang]

I have a Trend 300/1000 diamond plate, and I've used the 300 side for flattening 1000 and 8000 grit waterstones. I've done so a few dozen times now, and the 300 side already seems kind of worn out -- when I try to use it for sharpening a blade, it feels much less aggressive than the 1000 side, and it works more slowly. I have a very coarse ceramic stone (maybe 120?) that someone gave me and I think that if I tried to flatten that with the diamond plate, it would wear out the plate very quickly. Maybe if I had a higher quality diamond plate, this wouldn't be as much of an issue? I don't know.

The other thing about my diamond plate is that it's not quite flat. Its dished on the 300 side such that when I put a straightedge along its length, I can fit a 0.05mm (equivalent to 0.002 inches) feeler gauge in between. Maybe it's a good thing that the 300 side of the stone isn't very good at cutting steel anymore, so that I don't get tempted to use it for "flattening" the back of a blade but actually make it convex.

[Derek Cohen]

Winston, this "wearing" of your diamond stones is normal. As these stones are broken in, they appear to cut less aggressively. I emphasise that this is par for the course. What is happening is that the high spots are being levelled. Diamond does wear, but I believe that it will wear far less if you keep the 300 grit for just flattening your waterstones.

Regards from Perth

Derek

[Winston Chang]

I went and got three paver bricks from Home Depot. They appear to have more aggregate (little rocks) than the ones pictured in Kollenrott's book, but they flattened just fine. I also have some silicon carbide grit that I got several years ago, for use with a steel lapping plate. (I think it was a Veritas Steel Honing plate, and it was way out of flat, so I eventually tossed it in the recycling bin.)

I don't have an angle grinder, so I didn't cut any grooves in the bricks. These bricks seem to be more porous than Kollenrott's, and the lapping went OK without the grooves. I used 60 grit powder at first, with a tiny bit of dish soap, and then after they got pretty flat, I moved to 120 grit. I spent probably 30-45 minutes doing this. I made sure to collect the swarf and dump it outside, instead of letting it go down the drain.

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After drying them off a little bit, but while they're still damp, the surface is a bit reflective.

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Putting a straightedge on it, a tiny bit of light is peeking through. With the largest gap in this photo, which is slightly on the right side, a 0.02mm (~0.0008 inch) feeler goes a little bit underneath, but can't go all the way through. I could have kept flattening, but this is flat enough for my purposes.

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In contrast, my diamond plate is dished such that a 0.05mm (0.002 inch) feeler can fit between the straightedge and the plate.

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I have to say I'm very pleased with the results. I used one of the bricks to flatten my 1000 grit waterstone and it worked great. When the brick goes out of flat, I expect that re-flattening it will be a quick process. I'm happy that I can create and (re-create) a very flat surface at home, without having to spend lots of money on a fancy diamond flattening plate. I spent $1.20 on the bricks, and I probably spent around $10 on the grit.

As for whether this level of flatness is important: For the bevel side of the blade, I don't think flatness matters that much, but for the back side of a blade, it matters a lot. I have chisels and plane blades that are very slightly convex from previous sharpening systems I used, and I always had hard time getting the edges really sharp. Eventually I realized that the problem was that the convex shape made it so that, when working the back of the blade on a stone, the edge didn't always make contact. Once I figured that out and re-flattened the blades, sharpening has been a much faster process for me, and with better results.

[Winston Chang]

edited to add: Here's what Wiki has to say about clinkers: https://en.wikipedia.org/wiki/Clinker_brick

Interesting... Apparently, in Germany there are industrial standards for clinkers, and in it, it says they have low porosity. That makes sense -- the ones pictured in Kollenrott's book appear to be less porous and rock-filled than the paver bricks that I bough. I looked around at Home Depot for other kinds of bricks, but there weren't really any other options for bricks of this size. I would like to get ones that look like the clinkers that Kollenrott uses, but I don't know where I could just go and buy a few bricks like that.

[Tom M King]

Maybe look for a place that sells old, recycled bricks. The old ones from the early 19th Century, and back, had plenty of clinkers. You will also notice that Wiki article says that modern brick production (or something like that) does not produce clinkers. Look for the old black bricks.

When I rebuilt the top part of this chimney, from the middle of those second story windows up, the old bricks we bought included a lot of clinkers. No modern flue liners fit what we needed. I lined the whole chimney with them, and it has since stood through an earthquake. They really do make a clinking sound when tossed together.

[Günter VögelBerg]

Why not just flatten fine stone with coarse stone? I did this with waterstones for a long time and always thought it worked well. Now I use oil stones and don't flatten anything.

[Jim Matthews]

Amen, Reverend.

[Winston Chang]

Thanks to the magic of the Google Translate app on my phone, I figured out that the super-coarse stone that I have is a Sigma Power Ceramic 120. Definitely not something I want to use my diamond plate on.

The stone had a significant concavity (probably around 1.5mm along its length). Unfortunately, the stone is longer than the bricks, so if I were to try to flatten it on a brick, it would sort of ride on the brick and quickly give the brick a convex shape. I set it across two bricks spaced apart, to do some rough flattening. I tried to use the entire surface of both bricks.

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The two bricks of course aren't exactly the same thickness and don't have exactly parallel bottom sides, so this is only useful for rough work. After the stone got pretty flat, then I flattened it on a single brick.

in the end, the two bricks that I used were somewhat out of flat when I checked with a straightedge, so I spent about 10 minutes re-flattening the three bricks against each other with SiC grit. Now absolutely no light is visible under my straightedge when I put it on one of the bricks.

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This was a lot of work for flattening a single stone, but I unfortunately I don't know of a better way to flatten such a coarse, aggressive stone. In the future I won't let it get so out of flat to begin with, and then it shouldn't require this much work.

On another note, the bricks have been great for flattening my 1000 and 8000 stones. (They're actually combined in a single stone -- it's a Norton 1000/8000 stone.) As I mentioned earlier, my diamond plate isn't quite flat, and I've had two other diamond plates that were even more bowed. The ones that are guaranteed to be really flat are quite expensive, at almost $200 for the DMT Dia-Flat, and about double that for the Shapton. I have a couple plane blades that have raised corners from "flattening" the backs on my earlier bowed diamond plates, and this makes them difficult to sharpen well. Here's one of them:

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I still get a kick out of the idea that one can create a very precise flat object without using another flat object as the source of that precision. Here's a video I came across that talks about how the three-plate method is the source of precision for objects in the modern world.
https://www.youtube.com/watch?v=T-xMCFOwllE

[Stewie Simpson]

Winston; given the title of your opening post, its fitting the Sigma #120 is also referred to as the Black Brick.

Stewie;