Thread: Suehiro Gokumyo 20K

Well, I finally broke down and bought one .. mostly to scratch an itch.

This thing is a bear to flatten! I've been working on the back side to try to save the stamp. My DMT 325 is well worn, and not up to the task. Jamie, who knows this stone inside out, suggested 325 Wet or Dry. That has gotten me most of the way, but as we get closer and closer to the entire surface clean, the harder the going gets because so much surface area needs to be removed. I need a new DMT 325 anyway, but I'm wondering if I should also get the 220 DMT to speed things up?

Any advice from those that have been in this boat?

Originally Posted by Druid

Well, I finally broke down and bought one .. mostly to scratch an itch.

This thing is a bear to flatten! I've been working on the back side to try to save the stamp. My DMT 325 is well worn, and not up to the task. Jamie, who knows this stone inside out, suggested 325 Wet or Dry. That has gotten me most of the way, but as we get closer and closer to the entire surface clean, the harder the going gets because so much surface area needs to be removed. I need a new DMT 325 anyway, but I'm wondering if I should also get the 220 DMT to speed things up?

Any advice from those that have been in this boat?

60-80-100 grit sandpaper, choose one of them, get more pieces if you think one is not enough and when flat enough, go for the DMT. You won't be in the same situation again for a long long time with normal use of the stone, so getting a diamond plate for a single use on a single stone that's one step coarser than the other one you are buying, it's counterproductive. I bet for the price of that diamond plate, the seller of the stone would be more than willing to flatten it himself.

Yes, they are hard, I used a CNTG 140 that got it flat then soothed with a 400 and 1k from CNTG.

I did lap mine a few times, because it would leave a ragged edge. I ended up removing a bit of the top before it worked consistently well. I still have one corner that is low, and it will remain that way…

The CNTG 140 plate at 35 bucks, I think, is a great stone for lapping, if you lap a lot. If yours is out of flat a lot, I would go at least to 220 or whatever it takes to get flat, then smooth with higher grits, don’t think it matters if you use Diamonds or Wet & Dry.

I do refresh with a 400 then a 1k plate, just a few laps.

You will have to experiment with pressure and laps to get the finish you want. It was not for me, the no brainer that folks rave about.

It did take me a month or two to figure it out, for the stone to settle down, and get consistent edges from it. It is very easy, with some razors to take the edge too far and it will chip, so you have to find that balance point, based on your technique and pressure. The edge for me, is very reminiscent of film.

Followed with .50 and .125um CBN it is a nice edge.

That 20k made me glad I went for the Atoma 1200. The Atoma is superior to the DMT Dia-Sharp, and the Shapton DGLP in my experience. What I did with my 20k was start out with the 325 (D8C) and did the initial flattening, and then came in at 1/3 to go with the Atoma. The difference in effectiveness was startling the first time I did this. I went as far as I needed to go to have an unobstructed field for honing and no further. I figure I will get the rest of the grid over time, as I use the hone and continue to lap it. That corner is still got a long ways to go but I'm in no hurry.

Yup. Looks just like one of my corners, does not hurt anything and will waste too much stone to get it flat.

Thanks gents..

Jimmy, that is about where mine is now. Does Atoma use a different grit system than the Dia-Sharp, or is it that much finer? My Dia-Sharp 325 must be severely worn, because it gives the G20 a reflective, glass-like surface! But it still cuts SuperStones like crazy!

Originally Posted by Druid

Thanks gents..

Jimmy, that is about where mine is now. Does Atoma use a different grit system than the Dia-Sharp, or is it that much finer? My Dia-Sharp 325 must be severely worn, because it gives the G20 a reflective, glass-like surface! But it still cuts SuperStones like crazy!

The Atoma have a raised surface so stiction is no issue unless you never rinse it while lapping.
They also have a consistency of flatness that DMT doesn't have.

Originally Posted by Druid

Thanks gents..

Jimmy, that is about where mine is now. Does Atoma use a different grit system than the Dia-Sharp, or is it that much finer? My Dia-Sharp 325 must be severely worn, because it gives the G20 a reflective, glass-like surface! But it still cuts SuperStones like crazy!

Originally Posted by onimaru55

The Atoma have a raised surface so stiction is no issue unless you never rinse it while lapping.
They also have a consistency of flatness that DMT doesn't have.

What Oz said. You can buy 3 D8C DMTs for the price of one Atoma 1200, but if I knew then what I know now I'd have only bought the Atoma. It is in a class by itself. Once you have the plate they sell replacement stick on diamond skins that are not as expensive as the whole plate. As Oz said, they are far more accurately flat than the DMTs.

I've got the XX 120, the 325, 600, 1200, and 4000 DMT. Only the 600 is dead flat. The others are close, but it ain't horseshoes, or hand grenades, and flat is where it's at.

Only one thing. If you purchased your Gokumyo 20k from Tools of Japan (Stuart Tierney). he says emphatically that using a 1200 Atoma to lap it will void the warranty of the stone, due to particles of diamond breaking free of the plate and lodging in the hone. He recommends the Atoma 400 which I have used for nearly 2 years with great results. E mail him not me.

People must have a lot of time on their hands to try lapping a new 20k with a 1200 Atoma.