Thread: Lapping synthetic stones with wet/dry sandpaper

Hello,
I need some info on lapping waterstones. Ive read that waterstones from certain manufacturers do not recommend lapping on sandpaper. Ive read that grit fom the sandpaper can get lodged in the pores of the stone causing cross contamination. I may be wrong but is this just a marketing strategy to push people into buying the expensive diamond plates? Ive read that some people use Sic carbide loose grit. So wouldn't the loose grit also be likely to be embedded into the pores also? Sic carbide does have a tendency to fracture and break down finer as you use it.

I’ve used sand paper without issue. I use a diamond plate to maintain them, but sandpaper is nice to make the first lapping go a little faster. If you’re worrying about embedded grit I would think you could scrub it with a green scratchy pad under running water.

I use a DMT, they last for quite some time...so cost gets you ahead in the long run.

Originally Posted by Southbound

Hello,
I need some info on lapping waterstones. Ive read that waterstones from certain manufacturers do not recommend lapping on sandpaper. Ive read that grit fom the sandpaper can get lodged in the pores of the stone causing cross contamination.
....

I have felt this with the rubbing stone that expensive hones come with.
I have felt this with the Norton lapping stone... on Norton hones.
and Naniwa nagura rubbing stones on Naniwa hones.
A solution is to rub the hone with your hands and perhaps a bit of something that does
not shed bits under running water.

I have lately been using the small rust eraser under running water.

The good news is it does not get lodged so bad that it cannot be rubbed and rinsed off.
Even wet cloth under running water can rub it off but do not use that rag on your car.
You need to use a Wet/Dry paper. Once flat you can work the surface with
a bit of tile, stone or steel under running water to clear any bits.

Diamond plates are nice but not essential.

You can rub one hone with the next in sequence...

Way back when someone was selling slices of the Chinese hone of uncertain grit to
use for slurry generation on those questionable hones. I have been using that lump
to rub my Naniwa 12K and it has started to polish itself and works fine.

Rubbing the surface enough to clear any grit will not move it from flat.

A "finisher" in the 10-18K+ range can be permitted to dish a little...
the shallow dish will produce a micro bevel with a light touch.
Up to the last hone you want all the hones to have the same geometry
and flat is a good choice.

I have used sand paper and it works... rinse well.

On a new hone that has never been lapped, I generally flatten it on SIC wet/dry paper backed by granite. Then I do the final lapping with a Atoma 1200 diamond plate. If any of the SIC gets embedded in the stone, the diamond plate will fix that problem.

However, you can achieve the same end result using ever finer grades of wet/dry sandpaper. SIC sandpaper is available all the way up to 5000 grit, although sometimes the grits above 1000 grit are more challenging to find. If you hardware store does not have it, try an auto parts store in the paint and body repair department.

I sometimes use a 2000 grit sanding sponge to generate slurry on hones. I purchased the sponge at a local auto parts store.

It's my opinion that some manufacturers don't recommend using sandpaper because, hey!, that same manufacturer happens to make a $200-$300 lapping plate that is recommended for their stone. Not exactly an original thought, but I still get by with sandpaper and a DMT plate, somehow......

I've used 3m wet/dry sandpaper on almost all types of synthetic stones from naniwa, shapton, norton, and all the cheapies and never had issues one way or another. After lapping, I always give the synthetics a good rub down with the palm of my hand, but that's about all that's required in my experience.

Originally Posted by Butzy

It's my opinion that some manufacturers don't recommend using sandpaper because, hey!, that same manufacturer happens to make a $200-$300 lapping plate that is recommended for their stone. Not exactly an original thought, but I still get by with sandpaper and a DMT plate, somehow......

I've used 3m wet/dry sandpaper on almost all types of synthetic stones from naniwa, shapton, norton, and all the cheapies and never had issues one way or another. After lapping, I always give the synthetics a good rub down with the palm of my hand, but that's about all that's required in my experience.

I agree! Its just my opinion, but its them pushing that$$$ diamond plate. Is 220 grit sandpaper to coarse to lap finer razor hones? Im thinking of using 220 grit sandpaper, and after that use my king 1k to further smooth my stones. What are your guys thoughts about this? Also does it matter if its aluminum oxide paper or Sic paper? Sic paper doesn't seem to last as long as alumox, when sanding wood and metal, but i dont know about synthetic stones??

Originally Posted by Southbound

Im thinking of using 220 grit sandpaper, and after that use my king 1k to further smooth my stones. What are your guys thoughts about this?

I think 320 paper or 325 plate is a good place to start and then move up from there if necessary. I personally wouldn't want to go much below that unless I was moving some serious real estate on the stone, and even then I'd probably follow that up with a finer grit for a few laps to finish it.

The grit to use when lapping the stone depends on how flat the stone is to start with. If you need to remove a lot of material, then 220 grit may be needed. If the stone is nearly flat, then you might use 320 grit - 1200 grit. The first time you lap a stone, you generally need coarser grit, unless the vendor has done that part for you. Once it is properly lapped, you can usually get by with higher grits to maintain it.

I saw a Mastro Livi video in which he was lapping a Coticule. He recommended using another Coticule of similar size to get the job done. If you have two of the same or similar stones, that method works.

Originally Posted by Butzy

I think 320 paper or 325 plate is a good place to start and then move up from there if necessary. I personally wouldn't want to go much below that unless I was moving some serious real estate on the stone, and even then I'd probably follow that up with a finer grit for a few laps to finish it.

A feature of using a 320 DMT are the deeper scratches in the hone surface.
These scratches do not load up with dark swarf and are a nice indicator of hone wear.
When the scratches vanish there is a dish on the hone one scratch deep. Not quite enough
to trigger a lapping but if they are concentrated in the center run circles on the near and
far bit of the hone to level the wear out.
Watch for them they are nice indicators.