How much work to lap some naturals

I just picked up 3 mystery stones yesterday at the local antique mall. They smell like a farmer spilled some motor oil on them in '58 and then left them in an old run down barn since then. I gave them all a nice hot soapy scrub to clean them up, which has lessened the old oil stink quite a bit.

1 stone looks like the workhorse of the group. Its really used and awfully dished. Feels like all of the other hones I had held before I started honing razors. Probably really great for pocket knives and other tools. I would expect no more than 1000 grit out of this.

The other two are dark brown and awfully smooth. They were mostly flat to start with, and I couldnt wait. I pulled a razor from the restore bin and it seems that one cuts reasonably quick (4k ish) and the other looks to be a higher grit/slower stone.

Now, my actual question. How much work should be required to lap these things? My went at 1 last night for about 30 minutes with some 120 grit paper. I was able to remove most of the pencil marks, but not all. I went through 2 pieces of sandpaper.

This is far more work than my norton required to get flat. Is this normal? Do I just keep working? Am I changing the sandpaper often enough?

I'll post pictures tonight.

It depends. Some of the stuff I've lapped was a bear and took forever with the DMTC 325. On the + side, once you get a tough one lapped chances are you'll not need to do it again for a very long time if ever. Sounds like you've scored some cool rocks there. BTW, Howard (The Perfect Edge) once posted that oven cleaner is great for removing oil residue from old stones.

Regular old table salt? Would you have to encase it? Could you just fill a ziplock baggie with salt and put the stone in there with it? Maybe give it a shake every once in a while?

I did use a fingernail brush with a good quantity of hot dishsoapy water. There is a hint of oil residue left, but i was hoping that would go away with lapping.

So, it sounds like the suggestion is to get a DMT D8C for this lapping chore. I was thinking that by the time I finish with this task, I would have gone through enough sandpaper to make the DMT an inexpensive item. Now the tough part would be finding one in Edmonton.

Like Jimmy said, some hard stones can take forever. After wiping out a DMT325 in no time at all on hard naturals, I got a thick glass plate and loose silicon carbide grit. Put some water on the plate, add some grit and go at it. The bigger (and thicker - less distortion) the plate, the quicker you will get the job done. I use 80, 150, 320 and 600 grit - lapidary supply shops often sell it for use in rock-tumbling and the like.

Bio washing powder gets rid of the oil and smell for me - a fairly rich mix of powder with piping hot water in bowl, pop the hone in and leave it for hours (I give mine a good scrubbing with detergent first to get rid of anything loose before putting it in the bowl of bio).

Regards,
Neil.

As they've said, it depends.

Removing 1/8'' grooves from a surface of Aoto took me less than 5 minutes.
Straightening a C12K where a 1/32'' of material needed to be removed took me more than an hour.

Sparq can you remember my loong flatening piece of syntetic stone with a low grit grinding belt glued to it. It works well for most of my hones. But with some realy hard ones it will take few hours to flatten them if they are badly dished. My Charnleys took about 20-30minutes.

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Originally Posted by adrspach

Sparq can you remember my loong flatening piece of syntetic stone with a low grit grinding belt glued to it. It works well for most of my hones. But with some realy hard ones it will take few hours to flatten them if they are badly dished. My Charnleys took about 20-30minutes.

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How can I forget! It was a lapper's paradise. :)

I think I am going to try the silicon carbide grit. I can get it here in town and it is a whole lot cheaper than a DMT D8C. Plus, the rock shops in town sell it by the pound.

I assume that the grit gets washed down the sink when I am done lapping? Or is there a way to reclaim the grit?

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Originally Posted by dnjrboy

I think I am going to try the silicon carbide grit. I can get it here in town and it is a whole lot cheaper than a DMT D8C. Plus, the rock shops in town sell it by the pound.

I assume that the grit gets washed down the sink when I am done lapping? Or is there a way to reclaim the grit?

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You would have to be a very cheap person to reclaim the grit. ;) You can get a tube of valve grinding compound (with water base!) for $5 in Napa auto parts. Do not get one with vaseline as it may contaminate your stones.

i would not wash the grit down the sink it might plug it up. better off on a towel and warsh it when through.

Quote:

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Originally Posted by dnjrboy

I think I am going to try the silicon carbide grit. I can get it here in town and it is a whole lot cheaper than a DMT D8C. Plus, the rock shops in town sell it by the pound.

I assume that the grit gets washed down the sink when I am done lapping? Or is there a way to reclaim the grit?

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Rock shop grit is a good thing but nix the grit down the drain.

If you ever clog the drain with grit it will be as if you poured cement down the drain. Better to have a plastic bucket of water and wash the grit off there. After a couple of hours decant (pour off) the water from the top and eventually let it dry. When it is mud, muck it out of the bucket on to old news paper and toss it in the trash. Once or twice down the drain is no big deal but it adds up over time.

If you want an adventure you can try to separate the coarse from the fine by
pouring off the 'grey' water and leaving the sandy grit on the bottom. The grit from the bottom can be used on a lap plate over and over until it is spent but do not bother, remember that you have no idea what grit size it is anymore.

When I used to polish rocks we had an iron lap plate that we would sprinkle grit on and polish the sample with finer and finer grit. We would wash the plate and sample of the previous grit and sprinkle a little bit of the next finer until done. We had a drain under the lap that went into a cascade of buckets so the mud and grit would settle out overnight prior to letting the water hit the drain.

As a side note.
When polishing a telescope mirror as a kid we would suspend the polishing rouge in water. Early in the polishing stage the suspension would stand for
only a min. As the polish got finer and finer the timer was set longer and longer before we would slurp off a charge with a turkey baster.

grit from the rock store rocks. I made more progress in 10 minutes tonight than I did in 30 minutes last night using sandpaper. I just put the grit on my granite floor tile, tossed on a little water, and went to town. Worked great.