Lapping question

[Jakebullet]

I lap my Naniwa and Welsh slate on a piece of 320 grit sandpaper on a tile. I see a lot about avoiding contaminating a finer grit with a coarser one.
Does a 320 grit sandpaper leave 320 grit scratches on my 12k stones? Should I use a sandpaper close in grit to the stone?

 

[Proinsias]

Should be fine but you can go finer to 600 or so, a worn in piece of 320 grit can do a similar job.

* or you can rub the stones of each other too

 

[SliceOfLife]

Generally a finer abrasive isn't going to trap a coarser one... at least not well enough that a good wash won't get rid of it. Not saying it's never happened, but it's not something too worry about. Stones with big pores like coarse washita... maybe... but it'll wear out/escape so fast in use on those hones it'll never cause a problem.

 

[Gamma]

Since you are already lapping your stones with this W/D - you would be able to see if there are scratches on your hones. .

The possibility of leaving grit behind when using sandpaper does exist. SIC particulate can embed into a softer stone. Will it happen? Depends on too many factors to discuss here. I wouldn't worry about it so long as the stone is cleared well after lapping.
Synthetic stones will get scratch marks from W/D paper , but those stones are almost self-healing because the binders are desgined to break down continuously. Unless you have literal cornrows in the working surface, I wouldn't sweat it. You could always run a Nagura over it to smooth it out. Worn 320x paper to lap a 12k is fine. Going finer just slows things down. I usually use a worn 400x plate on everything.
The Welsh slate might show scratches more easily and hold onto them longer. You do want to make sure that any 'felt' scratches are removed. Again, a worn 400x plate usually does the trick for me. If not, 600x w/d will clean it up.

 

[Steve56]

might try rubbing them together to smooth them.

 

[Slash McCoy]

I lap my Naniwa and Welsh slate on a piece of 320 grit sandpaper on a tile. I see a lot about avoiding contaminating a finer grit with a coarser one.
Does a 320 grit sandpaper leave 320 grit scratches on my 12k stones? Should I use a sandpaper close in grit to the stone?

The sandpaper is excellent for leveling the stone. Yes, the surface of the stone then will be about as smooth as the sandpaper. Temporarily, time depending on how hard the stone is. Generally a synthetic stone will not trap loose sandpaper grit though in theory it should be possible. But as for the surface, first of all for a stone finer than 8k or so, it is a good idea to follow the lapping with 400grit with something finer. Not absolutely necessary, though. Second, you can burnish the surface by honing a large straight edged kitchen knife, or rubbing it on the next finer or coarser stone a few laps. It doesn't take much at all. And in practice you really don't notice it much at all when honing. The first half dozen laps will burnish most common synthetic stones. If you want to be anal about it, do 3 or 4 laps and then swap ends so you hone off the other long edge.

Black or trans arkies and some other hard naturals will need burnishing more, and it will be more of a chore.

 

[davidjohnwalter]

I lap my Naniwa and Welsh slate on a piece of 320 grit sandpaper on a tile. I see a lot about avoiding contaminating a finer grit with a coarser one.
Does a 320 grit sandpaper leave 320 grit scratches on my 12k stones? Should I use a sandpaper close in grit to the stone?

I AGREE BUT I LIKE 600 WET MAYBE EVEN 1000 ON A HUNK OF GRANITE FOR THAT FINE OF A STONE...DAVE

 

[Friedramen]

I AGREE BUT I LIKE 600 WET MAYBE EVEN 1000 ON A HUNK OF GRANITE FOR THAT FINE OF A STONE...DAVE

I think your caps lock might be stuck there :/

 

[Slash McCoy]

I think your caps lock might be stuck there :/

My eyes couldn't take it any more. I had to hit ignore.

 

[davidjohnwalter]

My eyes couldn't take it any more. I had to hit ignore.

NO I JUST HAVE VERY BAD EYES 4 OPERATIONS ON EACH,DAVE