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Has the stone been flattened?
the black marks could easily be metal being removed. That woukd make sense.
Got pics?
"Life is too short for bad tools.".-- Pedder 7/22/11
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neanderthal57 said:
I have a Norton 1000/8000 grit Waterstone. When I use the fine side I get black marks after just a few strokes. Very soon the stone is covered. They come off fairly easily but I'm wondering what is causing them.
When I'm polishing the bevel on a chisel, part of it will polish and then it seems to stop progressing. Is it the stone or is it me?
The black is metal being removed.
Consider flushing with more water (one of the downsides to waterstones is needing to manage all the water). Also consider getting a nagura stone to keep the surface dressed and a nice fine slurry present on the stone.
I switched from water stones several years ago to diamond stones (& strop) and now to oil stones & strop as my daily sharpening media. Other than a bit of a mess and some maintenance issues I was very pleased with the edges I got from waterstones. Just didn't like having to give up the space to the water management side.
Don't sweat the petty things and don't pet the sweaty things. -- G. Carlin
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The same thing happens with mine, always. Only the 8000 stone. I just add a splash more water and keep on going. Two or three strokes with a diamond plate after each use keeps it flat enough and exposes a new, clean surface. The 8000 is a fantastic stone.
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You might also try adding a drop of dishwashing detergent to your water that you use to soak and spritz the stone. It'll help keep the swarf in suspension, rather than adhering to the stone.
Still Learning,
Allan Hill
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The black means the stone is doing it's job of abrading the metal.