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Lapping waterstones for Straight razors

Posted by bricklayer 
Lapping waterstones for Straight razors
February 04, 2019 11:22PM
I need some of you fellows expertise on lapping waterstones for straight razors I dont have much experience with these type of stones. I just bought a Kuromaku 1.5k, 5k, 8k, and a Naniwa 12k specialty stone. I was doing some research and from what I gather they are not flat from factory, and can't have a fairly rough surface finish. I dunno yet, because I haven't received them yet. I have read also that its some kind a voodoo to lap with sandpaper because of contamination of grit into the stones.

I may be wrong but I believe those expensive diamond plates were over hyped by the Shapton glass, and Naniwa stones. Dont get me wrong one day I hope to get some Atoma plates. Some stone manufacturers say if you lap with sandpapers you will embed grit into the stone, so you have to use diamond. Some manufacturers recommend that you use the steel reference plate with loose SIC grit. I figured loose grit would be more likely to get embedded into the stone, but I have no clue. Right now I can't afford a diamond plate, that will have to be later down the road. So what grit of wet/dry sandpaper do I use to finish each stone? I was going to use 150 grit paper to get them all flat then progress to finer grits on each stone. I do have a 8×3 xxc Dmt that's never been used yet. I've had it for years for the purpose of reprofiling knives.

Another fellow recommended me to use and finish the surface with 220 on the 1.5k, 600 grit on 5k and 8k, and 800 on the 12k. He said that if you lap them crazy fine you will cause the blade to want to stick to the stone. He also said that he couldn't tell any difference in the scratch pattern left on the bevels when viewing on a scope, if you lapped the stones with a more coarse surface. That has me confused a little bit though . He recommended me to finish the 5k and the 8K with the same grit of (400 grit) sandpaper?? Wouldn't that make the 5 and 8k cut about the same?

I did some research on other stones and lapping plates, and the Shapton glass series recommends using their diamond lapping plate for all the grits they offer even the 30k glass stone. I think I read somewhere the plate is around 350-400 grit. So you would lap a 30k stone with a 400 grit diamond plate?? Looks like that would leave a very aggressive scratch pattern on the bevel plain?? I do have experience with vitrified stones like Norton InDIA stones, and if you lap them coarse they will indeed cut coarsely, and if you lap then fine they will cut finer, because they dont shed fresh grit, and they have to be periodically dressed .

On the other hand non-vitrified alum oxide or SIC stones they are not so particular, because they continually shead grit and expose fresh abrasive. Heck I've even took a Norton SIC stone and lapped it on a cinder block with great results, but if you do that with a vitrified stone you will only dull and round if the abrasive cutting points on the stone. My experience i like loose grit on vitrified stones. So how do these waterstones behave compared to what I am familiar with? How and what do I lap, these with? How to recondition/finish/ dress the final surface finish on each stone?

Greatly appreciated!
Re: Lapping waterstones for Straight razors
February 05, 2019 05:50AM
All i have to add is what I've done with my King 1K and 6K. I've never had to seriously lap the 6K, but I did the 1K after letting it dish.

I just used loose grit (I htink 36 grit? SiC) on a tile plate and got it flat. The surface if I recall did have some texture then, but I just lapped it a little more on a fine India or similar I think to smooth it out. I didn't really notice a difference in performance then the next time I used it...I think bc it sheds grit so easily.

For the 6K I just always flatten it after use, against whatever I have at hand. Sometimes it's a coarse Crystolon type stone, and then I just finish again on a smoother one I have to get rid of any visible texture.

I think by using the slurry on both, you quickly nullify any leftover surface conditioning. I can't comment on grit contamination though. I'm sure there was a piece or two I couldn't see, but nothing that really affected me by the time I worked through 1K up to 6K.

If Joe Calton doesn't comment I would write him too...he's been experimenting with all this a lot lately.


Always in search of a good choppa'
Re: Lapping waterstones for Straight razors
February 05, 2019 05:21PM
Don't worry about the sandpaper, if the SiC wet/dry is contaminating the stones you can use AlO which won't break down. Try the sandpaper on glass or marble or other flat surface. Find a good source of information, as there is a lot of misinformation out there. I like Lynn Abrams, Dr. Matt, Keith V. Johnson, Caleb McCollough and Devin Jackson (all on YouTube, most also on Facebook and Forums).

"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser

Jason D. Stone on YouTube
Re: Lapping waterstones for Straight razors
August 17, 2019 09:34AM
I just use a worn out smiths 325 interrupted diamond stone on all my Waterstones, from 220-12k, its the one that is around 11" x 2.5" that has recently been discontinued..... without that, I don't think you would have a problem with grit contamination. I think its pretty standard to lap Waterstones under running water to keep everything flushed out. and as fast as they release grit, you would be past any contamination very quickly. if you are worried, then flatten it with whatever you have, then take a junk blade and raise a light slurry all across the face of the stone and rinse it off.

Performance above all else!!!
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