Thread: Suehiro 20k lapping?

I shudder at the thought of lapping ANY hard hone/stone with a diamond plate.... I almost ruined my DMT 325 lapping plate on a couple of super hard barber hones back in the day. I stopped before I completely wore out the DMT, and it still works fine (but slowly) on typical man made hones like the Naniwa and Shapton Glass series, but I would not use it on a hard hone like the Zulu Grey and in this case it sounds like the Suehiro 20K is in the same league.

thebigspendur mentions the Shapton lapping plate, not to be confused with the Glass Diamond lapping plate or their other reference diamond lapping plate. It is just a flat piece of cast iron with a pattern in the surface and is meant to be used with loose SiC powders. This is the tried, tested and true lapping method machinists are familiar with. It's inexpensive and gets the job done, but it is messier than using a diamond embedded plate.

For simple/cheap, a flat concrete floor, a cookie sheet to contain the mess, some SiC particles and a bit of water will get the job done, saving your expensive diamond plates for what they do best, cleaning between honing razors on soft hones that load up with swarf.

DMT vs Atoma. I've used and own both.... I prefer the Atoma brand diamond plates. The difference is that while DMT evenly spreads their diamonds over the entire surface of their plates. Atoma makes little piles or buttons of the diamonds leaving empty space between them. Atoma plates suffer less from suction in use when flattening/cleaning hones.

I recently flattened the backside of my Zulu Grey 8" x 3" hone.... that is one hard rock and I promptly put away my diamond plates and brought out the lapping gear with loose SiC grit. I use the glass plate with plastic cover sheets from Lee Valley Tools. You could use just the glass plate, but you eventually dish it from lapping... By using the inexpensive plastic sheets, when it wears through, I just stop and replace it, but they are quite durable. I also mark the glass with a felt marker as to what grit I use on that side, then cover with the plastic and I don't have to worry about an occasional errant grit embedded in the plastic as it will always be the same size. But rest assured, even using SiC grit, that Zulu Grey hone took quite a while to flatten.

I don't worry about the finish of my hones..... the stria in the surface is just negative space and has no effect on the razors edge, unless it's super deep and at a 90 degree angle to the length of the hone. If the stria on the surface are large enough and deep enough to affect the edge of the razor, the hone would have to look like coarse metal file. I know some swear by "polishing" the surface of a hone, but that means you are knocking the tops off the grit in an attempt to reduce it's cutting effect. This is the method used with barber hones of yesteryear and today's Tormek water wheel grinder. The Tormek system uses a SiC two sided hone. The coarse side is used to rough up the surface of the wheel and expose fresh grit, and the fine side of the SiC stone is used to burnish and flatten the grit of the wheel without tearing the grit out of the surface, emulating a finer grit wheel. For what the Tormek is used for... it works fine, but for razors.... I dunno.... it's like taking a 1K Naniwa Chosera and after burnishing the surface claiming it is a 10K hone.... That just does not work for me.

So.... If it were me, I'd put the diamond embedded hones away, and instead grab some cheap loose SiC grit and lap that stone the old fashioned way.... I'm sure there are many sources for SiC grit, but if you are in a bind to find some, Lee Valley runs a internet mail order service and ships to the USA as well as in Canada. Shapton's loose grits are the same thing.... if you have a supplier of those, that's fine too. The only thing I would watch out for is the lapping compounds sold for lapping automotive cylinder head valves. It's the same grit, but it's mixed with mineral oil/grease to make it into a paste. You want the dry powder type and you want to use water for lubrication so it doesn't ruin your hone.

Regards

Christian

I have to be honest here, for me the 16k SG and the nani 12k ss get the edge right where I want it. With the fact that I live in a nice apt with no work space it and the lapping process for this Suehiro I would prefer someone to get the stone at a great price that would love to use it or need it for that matter. Do these Suehiro 20ks re sell well?

Originally Posted by dshaves

Is that the same as the Shapton glass lapping plate, because mine just skims over the stone and removes nothing!

No, this is a very heavy and dense steel plate.

Originally Posted by dshaves

I have to be honest here, for me the 16k SG and the nani 12k ss get the edge right where I want it. With the fact that I live in a nice apt with no work space it and the lapping process for this Suehiro I would prefer someone to get the stone at a great price that would love to use it or need it for that matter. Do these Suehiro 20ks re sell well?

I would say it is a niche market. Speaking generally. There are not lines of people waiting to spend north of $200 on a synthetic hone to finish straight razors. Of course we are talking theoretically, because we both know that it is not allowed to offer items for sale on the forum.

The classifieds 'strops & hones' section would be the place to offer a 20k for sale, should anyone ever want to.

Yup, before you spend a bunch more money on a lapping plate, spend $15 from GotGrit.com and get an assortment of grits 60 -500.

A dollar cookie sheet, like the Kaptian said, and put it on the floor, a tablespoon or grit, squirt of water and 15-20 min will get it flat.

The SG20 is hard, they will pull out diamonds, and that will cause you more problems, cause then you got to polish them out.

It is the next step up from the 12 and 16k. I refresh mine with an Ark. And if you get into Naturals, your all set for lapping...

You might try the other side, before you give up on it.

To satisfy my curiosity, could you do a pencil grid then do a quick 10 second lapping? Then post a pic on here.

Originally Posted by dinnermint

To satisfy my curiosity, could you do a pencil grid then do a quick 10 second lapping? Then post a pic on here.

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

Not to say that the recommendations mentioned are wrong, but my experience is different. I've used a dmt325, and only a dmt325 to lap all of my natural and synthetic stones. I have had zero problems whatsoever. The 20k was a pain and took longer, but it doesn't have to be "perfectly" flat. Just look at an old barbers coticule, most of them are probably picking up HBO they are so dished out.

Originally Posted by prodigy

Not to say that the recommendations mentioned are wrong, but my experience is different. I've used a dmt325, and only a dmt325 to lap all of my natural and synthetic stones. I have had zero problems whatsoever. The 20k was a pain and took longer, but it doesn't have to be "perfectly" flat. Just look at an old barbers coticule, most of them are probably picking up HBO they are so dished out.

+1 on the diamond plate. I'm willing to try new and different stuff, but for the past 8 years the plates have been my lapping mainstay. DMT, Shapton, and finally the Atoma.

I'm wondering how loose grit can be used and be uniform enough, under the stone, to do an accurate flattening ? I'm not gainsaying, particularly since I haven't tried it. When I picture the procedure in my mind's eye it just seems that some areas would have more grit collecting under the stone than others ?

As far as the 20k, here is mine long time ago. Still not much changed with that one corner that never got flat in spite of many bouts with the plates. There is adequate honing area, so if it never gets dead flat, no worries ..............

A quick quote from Wikipedia and yes, I know it's NOT the ultimate source of knowledge, but lapping has been done for a long time.... it's nothing new.

Taken to the ultimate limit, with the aid of accurate interferometry and specialized polishing machines or skilled hand polishing, lensmakers can produce surfaces that are flat to better than 30 nanometers. This is one twentieth of the wavelength of light from the commonly used 632.8 nm helium neon laser light source. Surfaces this flat can be molecularly bonded (optically contacted) by bringing them together under the right conditions. (This is not the same as the wringing effect of Johansson blocks, although it is similar).

The topic "Lapping" on Wikipedia appears to be well written and accurate as far as I can tell, and is a far more interesting read than I can write!

Regards

Kaptain "Ouch.... tripped over another word again....<sigh>" Zero


[Edit]

I'm wondering how loose grit can be used and be uniform enough, under the stone, to do an accurate flattening ? I'm not gainsaying, particularly since I haven't tried it. When I picture the procedure in my mind's eye it just seems that some areas would have more grit collecting under the stone than others ?

Yes, it does collect in hollow areas, but it only removes material where required and not where it's not required. Grit is sorted by sieving.... nothing larger than the holes in the sieve will get through. Smaller particles that do fall through, will have no effect on the lapping until the larger particles have worn down to the same size. Using a softer material for a lap allows the grit to grab hold and not wear the lap away as fast as what is being lapped. It IS important to remember that there is a skill involved to obtain a *flat* surface, no matter the tools. Highly accurate diamond plates do not guarantee the hone you are flattening will become perfectly flat. Using poor technique, you can create a convex or twisted surface quite easily. This of course applies for lapping with loose grit and a lap as well.

And just to clarify, it's not all that messy really, but it IS messier than using a diamond plate. And... you can use a flat counter top in the kitchen with that baking sheet. All that cookie sheet needs is a firm flat surface as by itself it's rather flexible.

A lap can be quite soft, such as the thin plastic self adhesive sheet I use on glass plates. Lead is also often used for a lap against steel, as is brass.... This may seem odd at first, but remember that wet/dry sandpaper is only a paper substrate with grit attached to it with glue, and yet you can sand away steel with it!