Lapping hones??

[Big.Dave]

I have some hones that have never been used to sharpen a razor but have been used to sharpen chef knives.
Needless to say they were badly dished to the point that if my old Japanese head chef saw them he would cut my nackers off with a very sharp sushi knife. I was a sushi chef for 4 years so learned about using the toishi (sharpening stone). In the past to lap them one of the guys would rub them on the back door step untill they looked flat ish we could make the blades sharp enough to shave with but I could not tell you if it would have been a comfortable shave but a drop of water on your arm and it would nock all the hairs off no problem.

Anyway back on track my stones were bad so I looked on SRP forum and followed their guide to lapping hones.
So I had on the kitchen work top 320 grit wet and dry paper water and a pencil stones in to soak.
First problem was I poured water on to the work top placed the wet and dry onto it and it curled up faster than you can say Jimmy Jack Jones so that was a pain but managed to reduce the problem by just wiping the work top with a damp cloth and pouring water on to the abrasive side.

I marked a grid on to the side of the stone that was to be lapped and off I went I knew this had to be repeated a couple of times because the pencil can get washed off.

Now the question I have is although it was taking the pencil grid off towards the end I noticed that in a couple of rubs it was coming of instantly but washing the stone and looking at it under a light I could still see it was not quite flat so I carried on untill I could see it was flat. Is this being OTT or will just being able to remove the pencil grid very very quickly be good enough?

Also towards the end of lapping I would begin to feel suction on the stone to the paper is this a good sign or a bad thing?

Anyway 2 1/2 hours later I had finished.
http://i770.photobucket.com/albums/xx349/Big-Dave-X10/2010-08-21200035.jpg
the big one I call the beast is a 1000 grit Japanese hard sinthetic stone I forget the make,the middle one again Japanese a double sided 800/1200 soft stone and the one on the right is between 1000-1200 but do not know the make it is hard.

I was told by the first Japanese head sushi chef I worked with (who's family had ran a sushi shop in Tokyo for at least 3 generations) that although it takes longer a hard stone gives a better edge and that a modern soft stone is quicker but does not give as good an edge my observation of this comment was Both did the job but he may have been right and that I had missed some small detail that he would know about but would not tell us because he was such an old fashioned Bastard!!! but thats another story. He would go 800/1000/sometimes 10000 on his knives the 10000 stone was only used when we had ViP's in and it would put a mirror finish on the blade.

After honing that lot with a big dollops of elbow grease I'm Knackered.

I would be interested to hear any comments on what I have done and is there anything I could do to improve even further what I have done so far.

 

[Neil Miller]

Usually its best to put a drop of water on the glass plate before laying the wet & dry paper on it - that stops the paper curling and 'sucks' it to the glass because of the meniscus attraction. If the paper is very thick/coarse/stiff it helps to soak it in water till it relaxes. Otherwise, it seems like you have it nailed. As long as it only takes a little rubbing to remove the marks you are done - remember, you are lapping relatively coarse hones here, so some of the graphite from the pencil is going down into the 'grain' of the hone. The suction is a good indicator that the stone is ready - you simply wil not get it with a rough surface in proximity to a smooth level one and it is once again a sign of meniscus attraction. They call it 'stiction' because of the sticking/suction that you feel. with very fine hones you can really have some trouble getting the hone off the lapping surface.

If you really want to get anal about lapping, get a diamond plate or an engineers surface plate (the latter to lay the wet and dry on - a foot square one will cost you about £70 and will be useless if you overshoot the paper on a frequent basis - they come in steel and granite).

With rough stones I simply bypass 320 grit and go to 100 - 180: makes the process much faster. You then only need a few intermediate steps, say 240, 325, 600 (anything over 325is just personal preference though).

The hard/soft stone thing is probably not important at this stage. Softer stones will release particles forming a slurry far more easily than harder stones will, and although this makes the cutting action quicker it will also slightly round the edge, leaving a less sharp edge than a hard stone. Also - to some extent - it depends on the steel which type of stone you use, but this is even more of an esoterical subject. In reality, the stones you have are in the bevel-setting range and the razors edge needs to be refined by, for instance, a series of stones like 2000, 4000, 8000, 10,000 grit. Roughly. To get a roughly acceptable shave (in the loosest sense of acceptable) you usually have to go at least to 4000 grit, and most people would not even consider shaving off a stone less than 8000 grit. Today most go for something like 10,000 - 12,000.

Regards,
Neil

 

[antdad]

I haven't needed to lap my hone's yet but I did need to knock up a large surface plate quickly for another purpose...used a thinish polished granite floor tile (available quite cheaply from a DIY shed) and bonded it to a few layers of thick ply. Worked well, very true and useful if you don't happen to have marble worktops.

 

[Arrowhead]

I use a machine bed with sandpaper to do the donkey work, and finish off on a diamond plate if I can be bothered. As Neil says, prising a flat stone off a plate can take some doing, so the perforated DMT type stones might be a better bet. Absolutely lousy for sharpening 1/8" chisels though.

 

[Big.Dave]

I haven't needed to lap my hone's yet but I did need to knock up a large surface plate quickly for another purpose...used a thinish polished granite floor tile (available quite cheaply from a DIY shed) and bonded it to a few layers of thick ply. Worked well, very true and useful if you don't happen to have marble worktops.

Following comments from the chaps on the form about steel and granite sufaces and running the risk of trashing one of my kitchen work tops and upsetting the misses. I went to a tile shop near my house they did not have any large granite floor tiles but they did have 1/2 inch thick solid marble ones when I told the guy in the shop I just want one he said I could have it

So that means I've been on the receiving of my first pif!! good man!!