Lapping advice

[shipr]

I have an old stone that's marked Japan on the end. As you can see its in serious need of flattening.
I tried sandpaper and it was working but the sandpaper gets clogged too fast. I think sandpaper will work great once its fairly close to flat.
Is there a better way to grind it down?

Also how do I determine the stone grit?

 

[jag613]

i use a drywall screen sanding mesh, i got it from the same section as the other sand papes in a hardware store. Wet/dry sandpaper works better than jsut normal sand paper aswell
What i would recomend first since it's pretty bad is to take it to a large brick or just some flat sidewalk to get it fairly flat then to sandpaper that's on something flat such as glass or granite.

cheers and goodluck!

 

[Leon]

Also how do I determine the stone grit?

You don't, simply put. Only by experimenting each side you'll find out what each stone will make to the edge of your razor.
Pick one straight razor that is not sharp and smooth, make 20 laps on one side, test it. If it's harsher, then chances are that this is coarser than a finisher stone.

 

[professorchaos]

You don't, simply put. Only by experimenting each side you'll find out what each stone will make to the edge of your razor.
Pick one straight razor that is not sharp and smooth, make 20 laps on one side, test it. If it's harsher, then chances are that this is coarser than a finisher stone.

What he said!

From the look of it, that is a fairly coarse stone. Looks can be deceiving so your best bet is to test it.

 

[shipr]

Thanks for the help grinding it on the sidewalk actually worked really well... and the mess cleaned up easy with the garden hose.
After I got it down I moved to the sandpaper for the finishing touch.

The stone is pretty soft overall but the dark grey is quite coarse. The lighter grey is harder and finer. (maybe a medium?)