India Stone Change?

R

Robert Ptacek

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Oct 8, 2013
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In old posts and catalogs the Norton India stone is 320 grit , recently I have seen it called 400 grit.Has Norton reformulated or just restated that itis more like 400 grit in performance?
 
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Norton's current grit chart shows three (actually, four) grades of India stone, in Coarse (CAMI 120-150), Medium (240-320) and Fine (320-400) and Extra Fine (400+). Maybe there's some confusion around which specific 'India' stones are being referenced, in other posts here and elsewhere. In particular, there could be some overlap between the 'Medium' and 'Fine', which are both in relative close proximity to that 320-400 range. Here's their chart, below:

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David
 
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I have noticed this as well. That on line supply houses are calling the fine India a 400 grit stone and it's always been 320. It could be they consider it 400 grit 'After Break In.'
Which I think is close. DM
 
David Martin said:
I have noticed this as well. That on line supply houses are calling the fine India a 400 grit stone and it's always been 320. It could be they consider it 400 grit 'After Break In.'
Which I think is close. DM
Click to expand...

Except that's not how grit is rated, so that would be disingenuous.
 
I've noticed the hecho en Mexico India stones don't break in like the U.S. made (early ) stones. So, it feels like a different grit than the U.S. made stone. More coarse. DM
 
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It's also possible that there's a different grit/bond ratio, bond type, and/or different amount of pressure used in the forming process. Also, the particular grade of abrasive is almost certainly a little (or even a lot) different.
 
I can't find an "extra fine" India stone anywhere in their (Norton StGobain) catalog. I can't recall ever finding a stone marked as such but I'd be interested in picking one up.
 
That 'Extra Fine' India shown in the referenced grit chart is a surprise to me also. I'm now looking at a couple other Norton catalogs that I've downloaded (.pdf) in the last couple or three years, and I'm not seeing an EF India listed in those. Maybe it's a typo or some other error, or maybe just a short-lived trial from Norton. I'd previously not heard of an EF India.

(In searching the web, I am seeing one reference to an EF India on a woodworking site; that post is dated from 2007 however. Might've been discontinued since then...)


David
 
I'm glad you 2 carried this discussion in that direction. As I've not seen a X fine India stone either. I would have purchased one had I came across it. So, a short run then discontinued makes sense. Searching in mine I have one. It is from Sticks and Stones in the Dallas, TX area. The box is labeled fine but going by feel there is no doubt it is noticablely finer. I'd say around 600 grit or that area. DM
 
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Still looking at the web, and seeing other literature from Norton describing their stone abrasive types and grit ranges. In their own descriptions, they reference a combination of India and Arkansas stones as covering the full range of grit/finish needs for most uses, with the Arkansas stones covering the 'Extra Fine' or 'Ultra Fine' end of the spectrum. Sort of makes sense, in that most steels that respond well in shaping/grinding stages to an India stone, could be finished and/or polished adequately enough on an Arkansas stone, most of the time. That might also explain, if the EF India ever existed at all, why it might've eventually been discontinued in favor of using the Arkansas stones for finish/polish work.

With all that being said, I can now see a search beginning for a 'grail' stone in the India EF grit, among fans of these stones. Looks like we already have a couple interested here. :D


David
 
Looking at online stores that sell these stones. It's interesting that Only the fine grit ratings have changes, for the stated Crystolon and India stones. The coarse and medium grits remain as have always been, agreeing with Norton's chart above. Is there some inflating going on or misinformation? DM
 
Could it be a misreading of the chart? In looking at the chart the only number on the same line with the fine India is P400. Is this the manner some are reading it? DM
 
David Martin said:
Could it be a misreading of the chart? In looking at the chart the only number on the same line with the fine India is P400. Is this the manner some are reading it? DM
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I could see that being a factor leading to confusion about the grit size. Depending on which standard one is referencing in the chart (P400, ANSI/CAMI, JIS, etc), and also looking at the gaps/ranges of grits in between each of the Indias listed, it leaves it somewhat open to guesswork. And it may also be that Norton fully expects the stones to fall within a range, instead of meeting an exact, specific spec for grit. I doubt any oilstone in the mid-priced range, such as these, would be that tight in spec anyway, and likely would show some variation within certain upper/lower limits.

I've never expected oilstones to be that tight anyway. They always seem to start out feeling coarser, and then at some point after some use, will settle into a more readable and predictable behavior. Hard to predict where exactly that'll be, from one stone to the next.


David
 
A range is good thinking toward this stone. Good point. I took my made in Mexico India stone, (a IM-313 replacement stone) and surfaced one side finer using a JUM-3 fine side crystolon and one other SiC finer stone. The result I like. It came out like a 2 sided fine and finer India type stone. One side closer to a 300 grit the other side like a 500 grit. More like a broke in early India stone manufactured from the plant in Troy, NY.. Some good stones came out of that plant. So, you can do some things with these that cannot be done with other stones. DM
 
I have one 1"x4" India stone that is an extra fine but I'm not sure if it is a Norton.
It is a great touch up stone.

Just recently I started to lap 2 old India bench stones and these have been the hardest stones to lap flat.
I am just using silicon carbide grit though, they would probably go faster on my diamond plate but I reserve that for easier ground stones.

I would like to try the newest Indias just to see the difference.
The bond is very hard on these old ones, even harder than the American Mutt stone as I just lapped that flat after a few months of hard use on it.
 
India stones are very hard to level. As they have strong binders. Much stronger than SiC stones. I would not use a diamond stones. I would continue to use the SiC loose grit on a area of rough concrete. It takes me about a 1/2 hour of rubbing to get the fine side level. Less on the coarse side. Stay with a coarse grit to prevent glazing. DM
 
David Martin said:
India stones are very hard to level. As they have strong binders. Much stronger than SiC stones. I would not use a diamond stones. I would continue to use the SiC loose grit on a area of rough concrete. It takes me about a 1/2 hour of rubbing to get the fine side level. Less on the coarse side. Stay with a coarse grit to prevent glazing. DM
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This is my first time trying to lap these and I can see now it is gonna take a bit more work to get them completely flat.
I think it would be easier with a real low grit but 60 is my lowest ATM so I'm going with that.

I'm pretty sure these old India stones would destroy most diamond plates with too much pressure.
 
Yes, rubbing it with your diamond stone will shear off it's particles. I think your 60 grit will do it but it takes some scraping. Use water with it too as needed. It's not a stone you can hurry and it will try your patience. Mark lines on it with a black felt marker so you can see your progress and keep at it. Realize once you do this it may not need it again, just depending on how much you sharpen with it and it will work like a new stone. A good thought. Good luck, DM
 
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