Grit rating of a Fine India

S

Slim7

Joined
Oct 11, 2015
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84
Hi,
Does anyone know the grit rating of the Norton fine India stones? I was curious what would be the appropriate grit of SIC powder to use to recondition the surface. These are vitrified stones and if one laps to smooth it will round/glaze off the abrasive and make it not so effective. . If one laps to roughly then it will cut more aggressive and act more coarsely than it needs to be. I think I read one time that it is 280grit??


Thanks
Mike
 
For Norton India stones I use 120 if it is just to level and clean up.
On beat up flea market stones I go as low a grit as I own, which is 30.

After you run it through the grit the surface will be a bit coarser but that doesn’t last long.
If I want to accelerate the process I will run the back of a wide chisel over it for a bit.
 
According to one site:

Norton India and Norton Crystolon Grit Chart​

Stone TypeCoarse GritMedium GritFine Stones
Norton India Stone150240400
Norton Cystolon Stone120180320

However, I seem to recall my old Fine India being rated at somewhere in the high 200's to low 300's. Perhaps the rating has changed since I bought mine a decade or two ago.
 
Image below is a Norton grit chart, for their various products.

By Norton's own chart, they rate the Fine India comparable to something between 320 - 360 (CAMI - USA standard), or 400 (FEPA-P - European standard). In my own use, I've generally equated it's performance somewhere in that 360 - 400 ballpark. A little coarser when new - but then settling into the ~ 400 range as it's broken in. Though their comparison in the chart is in reference to waterproof sandpaper standards, in my own uses of both, it does closely compare to the finish left by those sandpapers as rated. So the comparison seems valid.

xnPDxhu.jpg
 
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Blues said:
However, I seem to recall my old Fine India being rated at somewhere in the high 200's to low 300's. Perhaps the rating has changed since I bought mine a decade or two ago.
Click to expand...

Norton has used essentially the same "Relative Sharpening Comparisons for Norton Stone Products" table from at least 2004 through 2019, the most recent I can find. The version above is from 2008-2009.

Obsessed with Edges said:
By the chart, the Fine India is rated between 320 - 360 (CAMI - USA standard), or 400 (FEPA-P - European standard). In my own use, I've generally equated it's performance somewhere in that 360 - 400 ballpark. A little coarser when new - but then settling into the ~ 400 range as it's broken in.
Click to expand...

CAMI and FEPA P are coated abrasive standards. A 2019 Norton flyer includes an infographic which more directly relates Fine India to a bonded standard, FEPA F. This shows the Fine India as 29µ, finer than 35µ from the table above. Astute readers may notice that the Norton Waterstones also bear a different micron rating. (I chose to use the old values in the GLGC since they have appeared repeatedly, rather than in a single brochure, and because actual usage reports state that the Norton water stones behave coarser than Japanese water stones of the same designation.) In either case this difference might be explained by the measurement apparatus. For example FEPA P2500 used to be specified as ~8.4µ by sedimentation tube (as seen in the table) but it is now specified as ~5.4µ by Sedigraph. This does not represent a change in the actual size as the apparatus is calibrated using a mastergrit.

JgHTF6s.png
 
I think I've had my stone since before I bought my home here...which is 18 years ago...so, it's probably 20+ years old.
 
The grit for that India was 320 for years. Then they bumped it up to 400.
I use 120 grit SiC to level it. And don't take it any finer. It will work back to it's original grit. On those stones that one leveling will last a long time. DM
 
David Martin said:
The grit for that India was 320 for years. Then they bumped it up to 400.
I use 120 grit SiC to level it. And don't take it any finer. It will work back to it's original grit. On those stones that one leveling will last a long time. DM
Click to expand...
I would say that the Behr manning or Bear brand fine India is closer maybe to a soft Arky in grit 450-500.
I have an old fine pike coming to me off Ebay next week , and it comes in wooden box with a lid and no hinges, I think its a factory box. Anyways it has Pike in faded writing of the backside of the stone and fine India on one end of the stone. So I don't know if that would put this stone older than the behr manning or the 'bear brand'?
 
David Martin said:
I have one of those and they are a step finer. They were mfg. in the New York plant. DM
Click to expand...
Nice. So are those some of the earliest fine India's? Earlier than Behr manning or bear brand? If so I have never owned one but I am told that they are finer and harder.. I think I got it at a decent deal, 40.00 shipped to me, it's a 8x2x1". My fine India stones I surface finish them with 150-180 SiC and imo I don't think it changes the grit rating at that, but it only makes it perform and cut like a really good '400 grit' stone.
 
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Correct, you cannot change the grit. Only the surface. Thus, it leaves a finer finish. Plus, on that stone it lasts a long time. DM
 
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