Thread: Suehiro 20k lapping?

The SG20k is a pretty hard (tightly bonded) hone. A new diamond plate of 325 grit or thereabouts will flatten it very quickly, but it will slow the plate down some afterward due to diamond wear. An old diamond plate that's got worn diamonds will take a dog's age to flatten the SG20k. Personally I find the best approach for flattening very hard stones/hones is - as already mentioned by several fellows - to use loose grit. You can take the stone/hone down to flat pretty rapidly this way, then give it a quick scuff with your preferred grit diamond plate to smooth it.

Another point I'd like to make is that there is some misconception about the "negative space" not doing any honing that I've seen mentioned by several fellows that isn't really completely accurate and isn't being thought through very well. Using a coarse grit to lap a hard stone can be bad news in terms of the finish that will be imparted by the stone afterward.

The "negative space" implication is that the surface of the hone is quite flat but has furrows plowed in that surface that are lower than the mean average surface height. This isn't really the case - in reality there are those furrows but there are also pointed peaks created as well - which break off easily during honing and create an auto-slurry which creates a coarser surface finish on the item being honed. Eventually this wears down to that flatter surface with "negative space" furrows, but until it does it is to the detriment of the created surface finish. This is much worse on harder hones (they take longer to wear down) and it's far worse of an effect when new diamond plates are used for lapping - they create deeper furrows and higher peaks than worn-in plates.

At 60 grit, you are hogging off material. On a hard stone like an Ark a tablespoon with water will get to flat quickly. The Silicon Carbide will thin out to a single layer of grit and abrade surprisingly flat and quickly.

Then it is just matter of polishing and refining. You can finish on Wet & Dry or a diamond plate if needed, on a SG20, 500 grit is plenty smooth and flat.

After 60 grit, the subsequent grits polish quickly. Just a few minutes, you can feel the smoothness of each grit.

You can get a ¼ pound of 60, 80, 120, 220, 320, 500 each for about $15, enough to do many stones.

It is much like honing on slurry.

If you think it's the diamonds getting "worn" I'd like to understand how and why with evidence. Diamonds are the hardest material known to man and I really don't think rubbing them on a stone is wearing them one bit. Now the steel plate holding the diamonds might be wearing out, and losing its hold on the diamonds, but the diamonds themselves are not being "worn".

Why buy all the stuff you don't need? Multiple types of loose SiC powders, a cookie sheet, a flat piece of tile etc? All you need is one dmt 325. Mine was purchased not long after I joined this site, so it's 3 years old and has never once been a problem. I think I paid $46 on amazon.save ypurself the time, money, mess etc and get a atoma or dmt diamond plate. You will never look back.

Originally Posted by onimaru55

You & I thinking the same thing here ? Stone is warped & he's trying to lap the convex side... which ain't gonna happen anytime soon

I'm also thinking that since so few laps are needed, just having a 4" or 5" area of flat should be more than sufficient to get the 20k finish on a razor. Might be a let down to use so little of an expensive hone. However, you're still getting the intended finish.

JimmyHAD's photo was exactly what I was trying to find (in vain).

Originally Posted by dinnermint

I'm also thinking that since so few laps are needed, just having a 4" or 5" area of flat should be more than sufficient to get the 20k finish on a razor. Might be a let down to use so little of an expensive hone. However, you're still getting the intended finish.

That was my thinking too. Eventually, if I live long enough, and hone enough razors, I'll continue lapping it and maybe even get down to flattening that corner. In the meanwhile it does the job it is supposed to do as is.

Thanks everyone, I decided to try and flip the process and put the DMT-325 in the hold and rub the stone on the plate. Wow what a difference....it cleaned up the stone super quick vs plate pushing into stone. I don't push super hard in to the stone or vise versa I learned my lesson with my Super stones warping the stone. I learned a lot here, really thank you for sharing!!!

Originally Posted by dshaves

Thanks everyone, I decided to try and flip the process and put the DMT-325 in the hold and rub the stone on the plate. Wow what a difference....it cleaned up the stone super quick vs plate pushing into stone. I don't push super hard in to the stone or vise versa I learned my lesson with my Super stones warping the stone. I learned a lot here, really thank you for sharing!!!

Oh yea, I always use the stone holder for the dmt. I learned the hard way with that, getting blisters in awkward places on both hands trying to hold the dmt. Glad you got it figured out.

Oops...diamonds., like any other physical substance is subject to wear and tear. They WILL flatten and become less effective in a grinding environment. The hardness of the material is no never mind.... Yes, they will resist wear longer than other materials, but they WILL eventually wear down.

“The diamonds likely aren't fracturing in the application of flattening stones, at least not after its been broken in. “

Of course, they wear, and pull out from the binder. They are hard, but not unbreakable.

They do fracture/wear, ask any good jeweler that looks at a lot of diamonds. People scratch glass with rings and fracture the edges and corners of Diamonds, all the time.

Most folks just don’t ever look at their rings with magnification to see how damaged they are.

Diamonds like any rock or gem are filled with inclusions, especially the lower clarity, use in industrial applications. Here is a quote from an article on Diamond Fracture Filling, a process used to drill out impurities/inclusions from Jewelry quality diamonds to improve clarity, so they can be sold for higher prices.

“Fractures are very common inside diamonds and are created during the diamond's creation in the earth's crust. As the rough diamond travels up from the earth's crust through volcanic pipes it comes under extreme stresses and pressures, and during this travel tiny fractures can form inside the diamond. If these fractures are visible and damaging to the beauty of the diamond, it will have much lower demand and won't be as salable to jewelers and the public, making them candidates for fracture filling and thus visually improve the appearance of the diamond.”

As many of us can attest, they do wear and an Ark, or other hard stones can trash a new Diamond plate in a hurry. So, call it micro fracturing or eroding, they do wear.

Diamonds and how we look and think of them, are in large part a result of an aggressive and successful marketing campaign. Diamonds are not as rare or indestructible as the De Beers, would have you think.

Originally Posted by Magpie

If water dripping off a roof edge can wear through a granite stone (so it took 100 years, so what!) then a solid material like a hone can certainly wear a diamond over time. Or are you going to argue that it was "really hard water"

Well, that's my point. They do erode, but no one will be around in 1 billion years to measure the .00000001 millimeter that goes missing....