I could use some help with sharpening stones ... lapping information and identifying

[mrapino]

Hello everyone,

Anytime I see a sharpening stone at a flea market or yard sale, I have to get it.

I've been accumulating a lot of stones lately, and I have a tone of them that I can't identify, and I don't know what their grits are.

Any opinions are welcome. I realize it is super difficult to identify over a photo, so no worries there.

My second question has to do with the maintenance of these stones. Most of the old ones are scratched, cracked, uneven, etc. I have been researching using Silicon Carbide powder to lap the stones, but I can't find a solid resource of information.

Someone told me that there is a difference between lapping natural stones and lapping man made stones.

They said that it doesn't matter how fine you lap your natural stones, they'll still generally cut the same either way. Like, if I have a soft Arkansas stone (equivalent to maybe 600-800?), and I lapped it with 400 grit SiC powder, it would still cut like a soft Ark (600-800). If I lapped the same stone with 1000 SiC powder, it would stil cut like a soft Ark (600-800). Is this correct?

Conversely, he said if you lap your man made stones with anything over the grit of that stone, you've ruined your stone. Is this true?

His example ... if you have a 150 Norton carborundum stone and you lap the 150 with anything finer than 150 SiC grit "You will have contaminated your stone".

Is there a place I can learn more about this stuff? I can't seem to find much info about it.

Any insight into A.) identifying stones from markets/sales, and B.) maintaining/lapping would be much appreciated.

Cheers!

FIRST STONE

SECOND STONE

THIRD STONE

FOURTH STONE

 

[David Martin]

Here's you some very recent information. http://www.bladeforums.com/forums/s...mic-stone-flattening-and-increasing-grit-size
Your first two look to be a Black Arkansas. DM

 

[bflying]

Many people just use diamond stones for lapping. But I use rock polishing media on glass, and works GREAT. Plus it's easy to find rock polishing sites with a simple search. I bought mine so long ago I don't remember where I got it. But a cup of a couple different grits go a long way.





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Sent from my mind....using Tap-a-Thought. (tm)

 

[mrapino]

Thanks guys!

 

[Gritomatic]

Fourth stone is either combo India+Crystolon or Combo India Coarse+Fine

Someone told me...

It was me. Nice to meet you here

 

[Jason B.]

The info you were given about lapping is not correct. It is correct in some ways but the explanation is all wrong.

It's not that you will ruin a 150 stone by using a finer grit compound but you very well might make the 150 stone much smoother. By using too fine of a lapping grit you "polish" the stones surface instead of refreshing it. It's easy to fix though, you just lap it with a coarser grit. This is actually very similar to what a glazed stones is, when a stone glazes over from use it's typically with tightly bonded stones that don't allow the abrasive to release and replenish. This means the abrasive particles get used beyond their service life and become dull which can lead to an array of sharpening issues. Diamond, Ceramic, Arkansas, and most Aluminum Oxide oil stones will all act like this to some degree.

Natural stones will lap similar to synthetic stones so just disregard whatever you were told.

How you lap a stone depends on the stone hardness and type of abrasive. Basically, there are two ways to lap stones, first is with a diamond plate and second is with a loose media on a hard surface. Diamond plate are great for waterstones of 320 grit or higher and loose abrasive is good for oil stones or coarse waterstones.


For the stones,

First stone, looks like a hard black Arkansas. Lap with fine Silicon Carbide powder. (220 grit)

Second stone, not sure but it looks like a medium Arkansas stone. Lap with SiC powder.

Third stone, maybe another hard black or some type of slate stone. Lap with SiC powder

Fourth,

Looks like a combo India in pretty bad shape. Lap on the sidewalk or Coarse SiC powder (60/80 grit).

 

[mrapino]

Fourth stone is either combo India+Crystolon or Combo India Coarse+Fine


It was me. Nice to meet you here

Nice!! Gritomatic, I hope you're not offended. I always cross reference information I receive with multiple sources. I am neurotic like that

I am so new to all of this, it's nice to get a ton of opinions, and usually over time you get some clarity based on whether there is a consensus or not.

I do appreciate everyone's input.

Thanks so much!

 

[Gritomatic]

With all respect to Jason B, I want to maintain my position.
For synthetic stones, I have used word "contaminate", not "ruin"
You are right about polishing effect when using fine lapping on coarse stone, but this effect is not important. What is important is a porous structure filled by large amount of abrasive particles hindering abrasive properties.
Nevertheless, I totally agree that coarse re-lapping is good solution to revive the stone.

Lapping of natural stones is different. "Glazing" is interesting term (can I use it in future?), not many people know what is it. It may happen on hard natural stones and hard ceramic when over-lapping with ultra-fine abrasives, and stone gets almost glass surface without abrasive properties. As far as I know, Glazing does not happens with Arkansas.
Second, the owner (or supplier) of natural stone can make 2 sides with different properties by different lapping. For example, our company supplies black Arkansas with one side finer that another. You never achieve this with bonded synthetic stone. example

 

[mrapino]

Thanks for this info. I just ordered silicon carbide powder last night. I got a pound each of 120 grit, 320 grit, and 600 grit.

I'm curious ... how fine is too fine? I figured 600 grit would be a good place to stop.

Thanks!

 

[Jason B.]

With all respect to Jason B, I want to maintain my position.
For synthetic stones, I have used word "contaminate", not "ruin"
You are right about polishing effect when using fine lapping on coarse stone, but this effect is not important. What is important is a porous structure filled by large amount of abrasive particles hindering abrasive properties.
Nevertheless, I totally agree that coarse re-lapping is good solution to revive the stone.

Lapping of natural stones is different. "Glazing" is interesting term (can I use it in future?), not many people know what is it. It may happen on hard natural stones and hard ceramic when over-lapping with ultra-fine abrasives, and stone gets almost glass surface without abrasive properties. As far as I know, Glazing does not happens with Arkansas.
Second, the owner (or supplier) of natural stone can make 2 sides with different properties by different lapping. For example, our company supplies black Arkansas with one side finer that another. You never achieve this with bonded synthetic stone. example

The stone will not become filled with abrasive, it just doesn't do that. Even if it did the loose abrasive has nothing to bond to and would fall or wash out of the stone. Regardless, it would smooth the stone and this is not at all what is wanted.

You may use glazing whenever you want

Arkansas stones can and will glaze, their abrasive is Quartz and because it is softer on the abrasive scale it will dull more rapidly and glazing will happen sooner. They say Arkansas stones are all pretty much the same grit size but the stone density is what makes them different. This allows them, as you know by your linked example to be lapped differently creating different surface textures and edge finishes. Over the years in this subform we have discussed this and also the surface texturing of Sintered Ceramic stones such as Spyderco ceramics. So yes, you can do this with synthetic stones, some waterstones can be altered in this way to though only for a short period.

My posts can be rather blunt, just how I am. No offense taken and none given, we are all hear to learn and share info.

 

[Jason B.]

Thanks for this info. I just ordered silicon carbide powder last night. I got a pound each of 120 grit, 320 grit, and 600 grit.

I'm curious ... how fine is too fine? I figured 600 grit would be a good place to stop.

Thanks!

The 600 could be used as a strop compound, the 320 will probably be good on fine stones (The first three you have pictured), and the 120 will probably be too fine for a coarse stone but be about right for a Fine oil stone (last stone pictured). The fine oil stone being in the 300-400 grit range. You really need the 60/80 for coarse stones or a flat section of concrete (driveway or sidewalk).

 

[eKretz]

The distinction between stones and the way they are lapped is not so much by natural/synthetic as it is by hardness. Very hard stones will hold onto much of the surface texture that is applied to them by either coarse or fine lapping. Soft stones will tend to default back to their natural state no matter how they are lapped because they just release any dull or glazed grit particles.

Glazing is not like an either/or situation - glazing is essentially just dulling or flattening/rounding of the abrasive particles, which is a gradual process. Mostly it's used to describe the point at which the cutting efficiency has dropped to a point that is too low for the intended or desired purpose. In addition to this, there's loading - which is when abraded particles get stuck in the voids of the stone/hone, preventing full engagement of the item being abraded with the abrasive surface.

 

[FortyTwoBlades]

The distinction between stones and the way they are lapped is not so much by natural/synthetic as it is by hardness. Very hard stones will hold onto much of the surface texture that is applied to them by either coarse or fine lapping. Soft stones will tend to default back to their natural state no matter how they are lapped because they just release any dull or glazed grit particles.

Glazing is not like an either/or situation - glazing is essentially just dulling or flattening/rounding of the abrasive particles, which is a gradual process. Mostly it's used to describe the point at which the cutting efficiency has dropped to a point that is too low for the intended or desired purpose. In addition to this, there's loading - which is when abraded particles get stuck in the voids of the stone/hone, preventing full engagement of the item being abraded with the abrasive surface.

^This.

 

[folder geek]

Over my head but I will reread this several times. I know there is some really good info here.
Cheers

 

[Gritomatic]

The stone will not become filled with abrasive, it just doesn't do that. Even if it did the loose abrasive has nothing to bond to and would fall or wash out of the stone. Regardless, it would smooth the stone and this is not at all what is wanted.

For bonded synthetic (which is the majority of synthetic stones) contamination is real thing. I'm ready to sacrifice one of my coarse stones and make short video of contamination.

Arkansas stones can and will glaze, their abrasive is Quartz and because it is softer on the abrasive scale it will dull more rapidly and glazing will happen sooner. They say Arkansas stones are all pretty much the same grit size but the stone density is what makes them different.

I never heard about glazed Arkansas stones which completely lost abrasive properties. The Arkansas is wonderful natural stone because of unique crystalline structure. No matter how you treat Arkansas, edges of fused grains (on surface) remain sharp. If you lap Rozsutec with loose #1200 SiC powder, 100% it will be glazed and lose abrasive properties. How you lap black Arkansas to do the same?

No offense taken and none given, we are all hear to learn and share info.

I hope so! Truth is born of argument.

The distinction between stones and the way they are lapped is not so much by natural/synthetic as it is by hardness. Very hard stones will hold onto much of the surface texture that is applied to them by either coarse or fine lapping. Soft stones will tend to default back to their natural state no matter how they are lapped because they just release any dull or glazed grit particles.

Thank you, hard & soft lapping distinction is better than natural and synthetic. Natural Soft Arkansas is in "Soft" group, while synthetic alumina ceramic is in "Hard" group.

 

[HeavyHanded]

My 2 cents:

ID of these stones already appears to be correct.

I would make sure to get 60 grit SiC for lapping. In many respects its all you need, certainly nothing finer than 120 or 220 at the most. The SiC grit breaks down rapidly under a lapping operation and becomes finer within minutes of use. Even on a finer stone, you can simply prolong the lapping a bit and will be effectively using a much finer abrasive than you started with.

If the abrasive is too fine to start it will do a poor job. The abrasive wears the surface instead of refreshing it - glazed.

In my experience Arkansas stones can and will glaze from lapping with a fixed abrasive or too fine of a lose one. They will also glaze if used dry or with water but takes a few for that to happen. Is a problem easily avoided.

If used carefully, an Arkansas stone that has been lapped with a relatively coarse abrasive will break in nicely with a bit of use and end up at its optimal surface based on density. Attempting to make it finer than its inherent properties will result in a slow cutting surface with low abrasive potential - very frustrating!

Lapping it to a rougher surface than its density would indicate will result in the stone simply breaking in, it won't stay that way - use the back of a chisel or similar or just use it and over time if not abused it will end up perfect. This can be sped up by lapping with finer, but since these are natural stones you have no way of knowing what the best expression of the surface will be without trial and error of different lapping grit, or just using it after a relatively rough grit lapping.

YMMV
Martin

 

[mrapino]

Fantastic discussion! I am learning a lot, and beginning to grasp how to approach the various stones I have to lap. I went ahead a purchased a more course Silicon Carbide powder. I got 1/2 lb. of 60/90 to go with the 1 lb. each of 120, 320, and 600 that I purchase first.

From what I am hearing, 60/90 - 320 is a good range for everything, and anything finer than that isn't necessary in 99.9% of situations unless I am using it to make into a compound from stropping?

I'm sure there is going to be a level of trial and error, but it is nice to know that if you lap with too fine a powder, you can correct it by re-lapping with a courser material.

The only sticking point for me is this ... for stones that I purchased in already poor condition, where I don't know how it is supposed to cut normally, how will I know how to lap it to bring it back to it natural sharpening capabilities?

I have stones that I don't really know what their natural coarseness is, like stone #2 in my original post ... I don't know if that is an 8000 grit finishing hone, or maybe it's just a really glazed stone with a courser grit ...

Or stone #4 ... it's probably a combination India in bad shape, but I don't know what grit the red and black sides are supposed to be.

Maybe I am being to critical, and it doesn't matter that much?

I'll use Soft Ark again as an example. So, according to some info from above, a Soft Ark will retain its natural cutting regardless of how it is lapped? Arkansas stones go by density, so the 600-800 grit designation is really just a way to equate the Arks in comparison to stones that DO go by grit ... that being said, since the "crystalline structure" never changes, whether I lap using course, or fine, the crystalline structure is still the same.

However, since other stones are bonded particles, these particles can be altered according to the lapping material you use?

PHEW!! You need a PhD to use and maintain sharpening stones?!?!? haha

Let's all pool our knowledge, and make a chart ;-)

 

[Jason B.]

The stones are roughly,

#1- 6000 grit
#2- 800-1200 grit?
#3- Maybe 4k or 6k like the first stone
#4- About 100 grit on the black side and 300 grit on the red side.

To start I would lap all but your first stone with the 60/90. You might need to mix some 120 in with the 320 to then re-lap all but the last stone (India stone). Maybe try just the 320 grit powder first then do a test sharpen, if you notice a high gloss finish over a visible scratch pattern then the lapping was probably too fine. When you Glaze over a stone like that it tends to feel slick while sharpening and overly polish the bevel. If it does this mix in a little 120 grit or use straight 120 grit. FYI, just a pinch is all that is needed, adding handfuls or even spoon full will just make a mess.

Martin (HeavyHanded) is well versed in Arkansas stones and Oil stones so I would pay attention to his advice.

 

[Gritomatic]

...unless I am using it to make into a compound from stropping?

Making a home compound from SiC fine powder is impractical. 2 reasons:
1) Industrial requirements to grain size distribution, quality and purity of material are higher for compounds, and lower for generic SiC powder. Compounds you can buy will be probably made in the USA. Generic SiC powder is probably made in India or China. It's okay to use it for lapping (because large grains disintegrate rapidly), but could be bad for sharpening.
2) Handling F 600 SiC and finer could be mess because it is airborne. Particles are so small and so light, tending to sputter as aerosol when you touch it. SiC aerosol will fly and cover your table, all surrounding object, you inhale it - not healthy. It's difficult to clean powder like F 1200 and finer because it penetrates consumer vacuum cleaner filters (except wet cyclone ones).

There are lots of good fine compounds. I would avoid fine SiC powder.

 

[HeavyHanded]

Washington Mills is a huge SiC manufacturer in the US, but I'm not sure if foreign sourced materials would be inferior, the manufacture of SIC is pretty well understood.

SiC and AlumOx are both listed as an "Irritant" so as long as no long term or high concentration exposure the body will clear odd contact just as it would airborne silicates. Anything under about 4 micron can be aspirated directly into the bloodstream, but stuff as large as 20-30 micron can be absorbed by the digestive tract. If handling a lot I'd recommend a respirator, otherwise just use care.

The biggest issue with graded SiC is that the grading process seems to round off many of the sharp corners and becomes jelly bean shaped. You'll need a very tacky binder to get a good honing polish with it - it will do a great job surface polishing as is. With a binder that makes it stay put, it will make every bit as catchy an edge as AlumOx or any other abrasive by size, and seems to work better on HSS or steels with larger non-Vanadium carbides.

Lacking a tacky binder, one could use the stuff busted off of a silicon carbide stone as it will have much sharper edges and works very well as an improvised stropping compound - is more forgiving of how its applied.

https://www.youtube.com/watch?v=DF2Y7Hha0MQ

You can try the 600 for a compound but will get better results reclaiming the abrasive from a stone, use the 600 for cosmetic polishing.