How is grit determined?

This is actually my first post on SRP - so happy I'm finally getting involved. I'm much more active and knowledgeable in the knife community at kitchenknifeforums.com, and have a respectable collection of Jnats, with a dozen or so other hones from around the world, as well as a dozen or so synthetics. Anyways, oddly enough, I've found it nearly impossible to find an answer to how grit is determined in synthetics (this question can't really be applied to naturals as we use synthetics to reference estimated grit in naturals, and the abrasive density is much less uniform in naturals than synthetics, obviously).
Does anyone know, especially in JIS and AISI? I think I once read long ago that it's the average density of abrasive particles in 2.5cm^2, but that seems like an odd and arbitrary number. Any insight would be appreciated.

Thanks!

It has to do with sedimentation rate, or at least that's how the finer grit particles are separated. Here's a table with the particle diameters of common synthetics, along with some natural stones, which I'd take with a grain of salt.

grit particle size

Quote:

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Originally Posted by KenWeir

It has to do with sedimentation rate, or at least that's how the finer grit particles are separated. Here's a table with the particle diameters of common synthetics, along with some natural stones, which I'd take with a grain of salt.

grit particle size

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Thanks. I'm also aware of this chart, which is a bit more comprehensive.

I guess a better way to state this is 'how is grit measured'? It certainly is a function of particle size, but what about the area? Is it squared, ie sandpaper, or cubed, ie stones? Or something else entirely?

No, it might as well be thought of as arbitrary.
1k grit shapton isn't the same as a 1k norton

1k grit sandpaper in the us isn't the same as 1k sandpaper in uk

Edit: there's no hard and fast rule, this grit has this size particles, because every manufacturer is different.

Edit2: other considerations might be how well the particles are bonded, that will control how much slurry you generate, and how jagged or smooth the particles are. One manufacturer may use smaller particles than another, but if those particles have more sharp corners/edges it may still cut faster than the stone with larger but smoother particles. Other manufacturers might be using different materials all together, which may cut differently

Edit3: each manufacturer may have its own formulae for max, min and avg particle size for each grit, but there isn't really anything industry-wide because every manufacturer is different.

Welcome to SRP, just to add to the confusion .......... from '09, by smokin'tbird ;

http://straightrazorpalace.com/advan...tml#post446896

I love it! :rock:

As far as how a manufacturer determines what grit to call a product, its approximation. They'll either make their own abrasive particles or buy in bulk, adjust binder strength, binder to grit ratio and overall density to get the final product some where close enough to what people expect out of a certain grit, let's say 4K, that they can get away with calling it 4K, instead of 3379 or 4400.

Quote:

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Originally Posted by KenWeir

No, it might as well be thought of as arbitrary.
1k grit shapton isn't the same as a 1k norton

1k grit sandpaper in the us isn't the same as 1k sandpaper in uk

Edit: there's no hard and fast rule, this grit has this size particles, because every manufacturer is different.

Edit2: other considerations might be how well the particles are bonded, that will control how much slurry you generate, and how jagged or smooth the particles are. One manufacturer may use smaller particles than another, but if those particles have more sharp corners/edges it may still cut faster than the stone with larger but smoother particles. Other manufacturers might be using different materials all together, which may cut differently

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Very much this.

Binder will have a large effect on a hone's performance. Barber hones are the perfect example of this.

Barber hone cutting material is actually in the range of 300-600 grit, yet a good barber hone will leave an edge equivalent to or better than an 8K hone. This is because those large particles are both very tightly bound - they do not break free or slurry - and they are very well worn. Almost dead flat with the surface of the hone and just barely poking up enough to remove a very small amount of metal. Those same particles in a loose binder that allows for slurry would wreak havoc on an edge.

It's quite an intriguing dynamic.

I'm at the point now where I am less concerned with any stone's 'grit rating' and more concerned with it's performance relative to a known quantity. For me, that's the Norton 1/4/8K because I own them and I'm quite familiar with those hones. YMMV.

Far t many variables to consider for there to be any simple formula.

:popcorn:

Here is the Glen system use it if you want

Grit

A Norton 1k is more abrasive then a Norton 4k which is more abrasive then a Norton 8k

A Naniwa SS 3k is more abrasive then a Naniwa SS 5k or 8k or 12K

A Naniwa Pro 1k is more abrasive then a Pro 3k or 5k or 10k

A Shapton GS 4k is more abrasive then an Shapton GS 8k

A Shapton Pro 8k is more abrasive then a Shapton Pro 15k

These are things I know :)

As soon as you move away from a Brand of hone or even a series within a brand of hone then you do not know any longer you are simply Hypothesizing

Any grit rating on a Natural hone is a WAG, (or marketing) and that is the Glen theory of Hones and Stones it has served me well for honing a couple of SR's :p

These are all great answers - thank you. Yes, less of a concern, and more of just wanting to see if anyone knew. An intriguing subject, especially since it varies from brand to brand. Sometimes I wish there was more oversight, but the variation is also part of the magic. Thanks!

Here is an interesting article on Grit Size of Silicone Carbide. Grit size and consistency would depend on it use and the quality of the product produces. For example, better quality stones would be more consistent, “graded grit” (at or near stated size), than cheaper stones that may use “ungraded grit”, or random size up to the stated grit.

“Silicon carbide occurs naturally as the mineral moissanite; however, it is extremely rare, only found in tiny quantities in a limited number of locations. All of the silicon carbide sold as an abrasive is manufactured. It is produced by placing a mixture of coke (a fuel and carbon source), sand (a silicon source) and sawdust (another fuel and carbon source) in an electric resistance furnace and heating to a very high temperature. The silicon carbide is then crushed and screened into specific sizes. These "grits" and "powders" are used as cutting, grinding and polishing media.”

“Some silicon carbide is sold as a "graded grit." That means all of the particles are very close to the same size. For example, an abrasive sold as "80 grit" would have almost all of the particles about 177 microns in size. Graded grit must be carefully crushed and screened to be sure that all of the particles are approximately the same size. “


“In contrast, "ungraded grit" has a wide range of particle sizes. For example, an abrasive sold as "60/90 grit" would have a range of particle sizes smaller than 60 grit (250 microns) but larger than 90 grit (166 microns). Ungraded grits do not require the same level of processing needed for graded grits. That allows ungraded grits it to be sold for a lower price than graded grits.”

High quality sand paper and Wet and Dry would do much the same, which is probably why you can easily see the difference in performance in quality, of Wet & Dry and sanding belts.

As with most things, everybody has their own “system/rating” and screed screens.

Quote:

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Originally Posted by Euclid440

Here is an interesting article on Grit Size of Silicone Carbide. Grit size and consistency would depend on it use and the quality of the product produces. For example, better quality stones would be more consistent, “graded grit” (at or near stated size), than cheaper stones that may use “ungraded grit”, or random size up to the stated grit.

“Silicon carbide occurs naturally as the mineral moissanite; however, it is extremely rare, only found in tiny quantities in a limited number of locations. All of the silicon carbide sold as an abrasive is manufactured. It is produced by placing a mixture of coke (a fuel and carbon source), sand (a silicon source) and sawdust (another fuel and carbon source) in an electric resistance furnace and heating to a very high temperature. The silicon carbide is then crushed and screened into specific sizes. These "grits" and "powders" are used as cutting, grinding and polishing media.”

“Some silicon carbide is sold as a "graded grit." That means all of the particles are very close to the same size. For example, an abrasive sold as "80 grit" would have almost all of the particles about 177 microns in size. Graded grit must be carefully crushed and screened to be sure that all of the particles are approximately the same size. “


“In contrast, "ungraded grit" has a wide range of particle sizes. For example, an abrasive sold as "60/90 grit" would have a range of particle sizes smaller than 60 grit (250 microns) but larger than 90 grit (166 microns). Ungraded grits do not require the same level of processing needed for graded grits. That allows ungraded grits it to be sold for a lower price than graded grits.”

High quality sand paper and Wet and Dry would do much the same, which is probably why you can easily see the difference in performance in quality, of Wet & Dry and sanding belts.

As with most things, everybody has their own “system/rating” and screed screens.

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Great info, thanks. Where did you find this? Anyone know of any companies that produce abrasive particles that might have more in depth steps regarding this process?

OK, OP:
http://www.engis.com/pdf/Particle-Si...s-summer07.pdf

~Richard

Just had to one-up us all, didn't ya?

:p