Hone flattening question...

[Magpie]

I have read a few times now people saying they use loose grit abrasives to flatten their water hones.

I have used this method to take down some hard Ark stones, but never on a water stone.

My question here is, Isn't it too risky? Wouldn't there be a likelihood of abrasive getting embedded in the hone? I cant imagine a soft stone like a Norton 8k wouldn't get something stuck in it somewhere.

Opinions?

[Aerdvaark]

I'm interested to know also, sure does seem likely to me too. I've only ever used DMT's for lapping my N8k.

[kaptain_zero]

Lee Valley recommends stopping at 280x for flattening water hones for that reason.

I use their glass/poly sheet lapping surface and I'm very happy with the 280x level which is where I leave my Zulu... In fact, I find it works better than the burnished finish the Zulu came with.

As for DMT and Atoma diamond plates... these can occasionally shed a diamond or two which could get embedded in a water stone. Always clean the surface carefully after flattening. Those who use a well used/worn diamond plate for cleaning and or creating slurry are pretty safe as the plate would have shed most loose diamonds by then, and they likely know how to deal with a chip or scratch in the bevel should such an event occur.

I made the error of using a brand new diamond paddle to raise some slurry on a Jnat..... I won't be making that mistake again!

There are exceptions, I'm sure... those Arkansas stones for one... they appear to require smoothing and burnishing to work from what I have read on SRP.

If anyone would like the little instruction pamphlet from Lee Valley, it's at Leevalley.com and you just search for 'lapping' and then click on the loose grit and accessories. You'll see a highlighted in blue 'Tech' and 'Instr' next to the set of 5 in the pricelist. Clicking on those will give you the pdf's and you can save a copy on your computer.

Regards

Christian

[Euclid440]

"Isn't it too risky? Wouldn't there be a likelihood of abrasive getting embedded in the hone?"


Yea, I would think so,

I have only ever used loose grit on hard naturals, I thought about using loose grit on the SG20, as that was/is a hard stone, mine still has a low corner.

But, that was exactly my fear.

[Steve56]

Loose SiC is a very aggressive way to lap a stone, very useful when you have badly dished, chipped, or abused stones to deal with. I can't imagine needing to use loose SiC on a synthetic waterstone unless it had been abused. Sandpaper on plate glass should work fine and is what I use for regualar maintenance of my synths.

I wouldn't worry so much about embedding grit in the synthetic stone, you'd likely see it (I use 300 SiC on plate glass) or feel it and be able to correct the problem pretty easily.

Cheers, Steve

[onimaru55]

There is a slight risk with soft stones but... If you have one of those Nortons that need the top skin removed, SiC is the best way to go.

I remember lapping an 4/8k Norton on loose SiC. You're pretty safe if you have a light hand. Heavy downward pressure will increase the risk of embedding particles. I did feel one spot where a renegade particle had adhered itself but ironically another quick lapping removed it.

You should test it with a sacrificial blade to be sure. If you have a a diamond plate for the final finish you're golden. I wouldn't hesitate to do it again.

[kaptain_zero]

I'm not sure if Shapton still sells them, but around the time Shapton hones became popular with Straight Razor users, they sold a lapping plate (cast iron I believe) and loose grit for lapping hones. They later came out with their diamond plates and I suspect they replaced the "cheap" lapping plate with it's loose grit.

There is ALWAYS a chance of a single piece of grit getting embedded in a soft or even hard hone, no matter the type of lap you use (diamond plate or sheet glass with loose grit). The safe way of using loose grits is to stay coarser than what you are lapping with a careful inspection of the surface afterwards, and the same applies if you use a diamond plate for lapping.

As far as accuracy is concerned, hand lapping was, and still is used to lap mirrors for astronomical telescopes, where accuracy far exceeds anything we need for straight razors.

Taken from Wikipedia:

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.

So... no matter what the manufacturers marketing dept. claims, us old timers will tell you that lapping with loose grit is time honoured and a perfectly acceptable way of flattening water hones or for that matter anything. All you need is some practice and some common sense.

Regards

Christian


(Now, if only I could remember how to spell.... I wouldn't have to do all these damn edits!)