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Post by Bob on Oct 2, 2020 14:56:25 GMT -5
When I first started rotary tumbling in 2014, and tried to come to understand the geology of what these rocks are, I knew very little. But I quickly grew frustrated about how a particular type of material would be called an agate on this website, a chalcedony on that website, a jasper on another! So I started studying mineralogy not to become an expert, but only to try to understand the rocks encountered in collecting and purchasing tumbling material. I first delved into the popular literature, and then deeper into scientific literature, with the goal of properly IDing every single one of them. This is when I learned the difference between a mineral, such as Prehnite, and a rock, such as Tiger's Eye.
So, completing that task took about 3 years and finally I finished it. There are still some materials for which I've never succeeding in proper classification, such as Sonora Sunrise Jasper, just to name one at random. By far the majority are merely varieties of the mineral known as quartz.
Coming to understand what I'm working with has led to a greater understanding of how a given material will probably behave in the tumbler. As I post messages about particular materials and what happened in my tumbling, I'm going to try to remember to include some comments about exactly what the material is to help educate my friends here with what I've learned. If feedback from others suggests this extra information is more of an annoyance than anything, of course I will stop. My goal is to share, not annoy. Many stores selling material don't know what it really is and perpetuate misunderstandings by labelling materials based upon what they saw some other store do.
If anyone is a mineralogist with expert knowledge and I make any mistakes, I eagerly seek correction and clarification too!
I will end this message with a comment about what there seems to be a really big misunderstanding about which is the word quartz which drove me crazy until I figured it out. This word is used in two very different ways.
1. Quartz is a mineral made of silicon dioxide, also called silica, and is the mineral with the most varieties, and most of all the materials we discuss are various varieties among the thousands of quartz. 2. Quartz is also used as a word to describe the quartz subgroup with a macrocrystalline structure, such as Rose Quartz, etc. This is the common use in a place where rock tumblers talk about things.
So when we say, hey, that rock on the right looks like Smokey Quartz but that other one below it looks not like quartz but chert or petrified wood instead, on one level we are screwing up because it is all quartz. This is where it gets confusing.
This word problem also occurs in biology. For example, someone says that's not a cat, that's a baby tiger! That person meant it's not a house cat which to them is a cat. Well, house cats, tigers, lions, jaguars, etc. are all members of the family Felidae, which are all cats. So in this way, the word cat in its usage is like quartz, it has two meanings.
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Post by Mel on Oct 2, 2020 15:05:23 GMT -5
I love this post Bob. When I first started tumbling, I just knew "this is quartz, and this is not" Learning the ins & outs of rocks has been a very fascinating journey. You can never know everything but it sure is fun to try!
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lordsorril
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Post by lordsorril on Oct 2, 2020 16:54:48 GMT -5
I remember having the Quartz/Chert---Chert/Flint---Flint/Novaculite---Novaculite/Quartz conversation with my gf. I think that is the last time she will ever ask me about Quartz again...
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pizzano
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Post by pizzano on Oct 2, 2020 17:22:17 GMT -5
Here are a couple helpful links that take further the notion that Quartz and Silica are related, but both have very different meanings and Crystalline characteristics...:
Having myself, misunderstandings while attempting various polishing methods and the use of various media and compounds, a little research helped a lot...!
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jamesp
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Post by jamesp on Oct 3, 2020 1:51:35 GMT -5
Here are a couple helpful links that take further the notion that Quartz and Silica are related, but both have very different meanings and Crystalline characteristics...:
Having myself, misunderstandings while attempting various polishing methods and the use of various media and compounds, a little research helped a lot...!
Quartz and silica are a challenge to understand pizzano. Lol I begin to try and run into the chemistry complexity required to understand it and throw the rag in every time. Dissolvable silica really gets complex but it is responsible for creating agates petrifications jaspers etc. For instance the quarries in Florida crush thick deposits of chert into road gravel. The silica source came from massive deposits of diatomic skeletons in limestone that were porous and able to dissolve easily to create the chert. Bamboo is loaded with silica. What's with that.
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pizzano
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Post by pizzano on Oct 3, 2020 9:11:58 GMT -5
Here are a couple helpful links that take further the notion that Quartz and Silica are related, but both have very different meanings and Crystalline characteristics...:
Having myself, misunderstandings while attempting various polishing methods and the use of various media and compounds, a little research helped a lot...!
Quartz and silica are a challenge to understand pizzano . Lol I begin to try and run into the chemistry complexity required to understand it and throw the rag in every time. Dissolvable silica really gets complex but it is responsible for creating agates petrifications jaspers etc. For instance the quarries in Florida crush thick deposits of chert into road gravel. The silica source came from massive deposits of diatomic skeletons in limestone that were porous and able to dissolve easily to create the chert. Bamboo is loaded with silica. What's with that. Yes indeed........I got curious when first starting out using a Vibe to polish and grind, with trying to wrap my head around how one Crystalline applied to another Crystalline of a harder or softer value, provided different stone surface textures.......specifically related to grit and polishing compounds. The chemistry aspect, in my case, set aside the "need to know" the scientific composition attributes........understanding, for my purposes, only the differences in silica values and how to apply those values to refine their polishing applications against mineral versus rock vibe processing, has been a challenge in it's self.......lol
Although, many media and compound manufactures (aside from being less transparent about actual texture values and grit sizes), have taken much of the guess work out of the application and processing for lapidary purposes, particularly as it relates to rotary tumbling. It gets a little more complex with vibe and blasting techniques, as you know with glass work and slurry binder applications.............but, once one understands and identifies the basic properties of the material being processed (agate, jasper, quartz, mineral or rock) and develops (either through personal or guided methods), a routine and confidence, the challenge only becomes duplicating the successes and learning from and not duplicating the errors made during the process.
Seldom do any two individuals in this hobby experience the same successes and failures with identical methods, tools and material.......that's the beauty of this hobby. But, individual study and help from proven successful and experienced RTH teachers and supporters, takes a lot of the frustration out of the learning curve we all have had, one time or another....!
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Post by greig on Oct 3, 2020 16:02:20 GMT -5
On other forums, I often see people posting pictures of raw "diamonds" which are quartz. It is a big help in rock tumbling to know if your rock is harder than quartz (eg corundum), same as quartz (7 on Mohs) or softer than quartz (eg. feldspar 6 and calcite 3).
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jamesp
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Post by jamesp on Oct 6, 2020 5:18:23 GMT -5
Quartz and silica are a challenge to understand pizzano . Lol I begin to try and run into the chemistry complexity required to understand it and throw the rag in every time. Dissolvable silica really gets complex but it is responsible for creating agates petrifications jaspers etc. For instance the quarries in Florida crush thick deposits of chert into road gravel. The silica source came from massive deposits of diatomic skeletons in limestone that were porous and able to dissolve easily to create the chert. Bamboo is loaded with silica. What's with that. Yes indeed........I got curious when first starting out using a Vibe to polish and grind, with trying to wrap my head around how one Crystalline applied to another Crystalline of a harder or softer value, provided different stone surface textures.......specifically related to grit and polishing compounds. The chemistry aspect, in my case, set aside the "need to know" the scientific composition attributes........understanding, for my purposes, only the differences in silica values and how to apply those values to refine their polishing applications against mineral versus rock vibe processing, has been a challenge in it's self.......lol Although, many media and compound manufactures (aside from being less transparent about actual texture values and grit sizes), have taken much of the guess work out of the application and processing for lapidary purposes, particularly as it relates to rotary tumbling. It gets a little more complex with vibe and blasting techniques, as you know with glass work and slurry binder applications.............but, once one understands and identifies the basic properties of the material being processed (agate, jasper, quartz, mineral or rock) and develops (either through personal or guided methods), a routine and confidence, the challenge only becomes duplicating the successes and learning from and not duplicating the errors made during the process.
Seldom do any two individuals in this hobby experience the same successes and failures with identical methods, tools and material.......that's the beauty of this hobby. But, individual study and help from proven successful and experienced RTH teachers and supporters, takes a lot of the frustration out of the learning curve we all have had, one time or another....! The Knoop hradness test is used on glass and ceramics pizzano. Different types of glass for instance can vary over a wide range between say a 'made up' Mohs 4.8 to Mohs 6.8. obsidian has a wide range of harnesses. Mahogany obsidian is one of the harder ones probably due to iron content. It can tell the difference in Mohs 5-6-7-8-9 hardnesses in decimal accuracies. It will tell the difference in hardness and toughness on crystalline verses cryptocrystalline quartz for instance. Almandine garnet is a perfect stone to focus on. It may be listed at Mohs 7 in some publications but it is more like Mohs 8 but way way tougher than most hard stones. For this reason it's Knoop hardness is about twice that of quartz. It is used on alumina, ziconia, SiC and a bunch of other oxide ceramic abrasives and engineered ceramics of many types. Of particular interest to rock tumblers: AO - 2100 SiC - 2500 Diamond - 7000 Knoop test shows the logarithmic behavior of mineral hardnesses. Mohs test does not. Maybe Boron Carbide at Knoop 2750 is a better tumbling abrasive. It may be totally expensive...
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jamesp
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Post by jamesp on Oct 6, 2020 5:28:42 GMT -5
Boron Carbide ?
Lapping Lapping is the most common final machining method for flat and plane surfaces. 3M boron carbide has a much higher hardness (Mohs 9.5+) than tungsten carbide (WC), titanium carbide (TiC), alumina (Al2O3), zirconia (ZrO) and silicon carbide (SiC). This high hardness allows fast and easy machining of wear-resistant hard metals and ceramics.
Ultrasonic Drilling of Glass, Semi-Precious Stones and Ceramics Ultrasonic boring is suitable for creating almost any desired profile in hard and brittle materials. 3M boron carbide has a narrow grain size distribution which allows for dimensional stability, contour fidelity and sharp angles at all corners in a single machining operation.
Wire Sawing of Ceramics with Boron Carbide 3M boron carbide is harder than alumina (Al2O3), zirconia (ZrO), silicon carbide (SiC) and synthetic sapphire. Due to its exceptional hardness, 3M boron carbide is well suited for wire sawing of oxide and non-oxide ceramics, and especially sapphire. When 3M boron carbide is used to saw ceramic materials, the cut surfaces have excellent quality with a planarity of ±5 μm, which makes lapping much easier and more cost effective.
No Go, 1/2 pound Boron Carbide 180 grit costs $29 on Ebay.
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Post by Mel on Oct 6, 2020 10:07:39 GMT -5
I wonder how much faster BC would do a rough grind than SiC in a rotary. Might be cost prohibitive but would time benefit be worth it? Not that time is a major concern with tumbling but interesting to think about.
Time is money after all (and I have neither so I guess my point is moot).
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Post by mohs on Oct 6, 2020 10:35:31 GMT -5
I've wondered about CBN grinding wheels for grinding rocks ? as anyone ever used one for lapidary rough grinding doming?
those types of wheels are real popular in the sharpening trade especially for H.S.S lathe tools and such...
Like to buy one for an experimental purposes
time , money little resources have to stick w/my worn out diamonds for now...
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Post by Bob on Oct 6, 2020 12:43:39 GMT -5
One big revelation for me, since you are speaking of hardness, was just how hard glass isn't. All my life, I have presumed that glass is super hard otherwise it would not last as long as it seems to in everyday objects. When walking along a river, or a beach, where people have been sloppy and thrown beer bottles, I've always been nervous about stepping on broken glass, especially because I like to walk barefoot. A few years ago, I realized I have been doing this for decades in a major sandy river in Oklahoma, and wondering why there seems to never been any sharp glass. Now that I've tumbled glass, and see just how much gets accomplished in just the first week in rough--even with sharp glass shards--I understand now why sharp glass edges in a sandy river don't probably last that long. I guess in a moving sandy river like the Cimarron or the Arkansas in Oklahoma, broken glass just gets ground to nothing and disappears perhaps within a month.
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jamesp
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Post by jamesp on Oct 7, 2020 6:33:33 GMT -5
I've wondered about CBN grinding wheels for grinding rocks ? as anyone ever used one for lapidary rough grinding doming? those types of wheels are real popular in the sharpening trade especially for H.S.S lathe tools and such... Like to buy one for an experimental purposes time , money little resources have to stick w/my worn out diamonds for now... Good question Ed. The BC may be way effective on lapidary materials. The individual cutting particles may maintain sharpness better than AO and SIC. It may not be near as brittle as silicon carbide, SiC is real brittle but real sharp. Super sharp is perfect for the low grinding pressures used in lapidary work. There can be a fine line between hardness and toughness or these two properties can dominate abrasion or cutting capability. A good example would be a tungsten carbide cutting tip that possesses enough toughness to cut into steel like it was butter for hours and hold its edge yet it is softer than aluminum oxide. Even diamond can not perform such a task.
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jamesp
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Post by jamesp on Oct 7, 2020 6:44:07 GMT -5
One big revelation for me, since you are speaking of hardness, was just how hard glass isn't. All my life, I have presumed that glass is super hard otherwise it would not last as long as it seems to in everyday objects. When walking along a river, or a beach, where people have been sloppy and thrown beer bottles, I've always been nervous about stepping on broken glass, especially because I like to walk barefoot. A few years ago, I realized I have been doing this for decades in a major sandy river in Oklahoma, and wondering why there seems to never been any sharp glass. Now that I've tumbled glass, and see just how much gets accomplished in just the first week in rough--even with sharp glass shards--I understand now why sharp glass edges in a sandy river don't probably last that long. I guess in a moving sandy river like the Cimarron or the Arkansas in Oklahoma, broken glass just gets ground to nothing and disappears perhaps within a month. Add some larger rocks with a batch of glass to increase the grinding pressure within a rotary and glass really rounds quickly Bob. Or use a vibe with a tall hopper that has higher 'head' pressure in the lower section of the hopper due to a tall column of rocks or glass to increase grinding pressure.
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jamesp
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Post by jamesp on Oct 7, 2020 7:12:01 GMT -5
I wonder how much faster BC would do a rough grind than SiC in a rotary. Might be cost prohibitive but would time benefit be worth it? Not that time is a major concern with tumbling but interesting to think about. Time is money after all (and I have neither so I guess my point is moot). BC Grinding wheels should be affordable Mel from Yuma & Spokane. Using BC in a vibe is probably affordable since the require small doses of abrasives. But we depend on abrasives breaking down to attain polish... A rotary sure gobbles up lots of abrasives during step 1. Can't see it being affordable for step 1 in the rotary unless the BC could be used over and over. (I could not find it in larger than 180 grit.) This brings up another question to ponder for step 1 in a rotary: What is the best size of abrasive particles to use in step 1 if the particles never broke down and stayed permanently sharp ? It is very possible that diamond abrasives would never get dull or break down during step 1 in a rotary. 3/8 inch SiC particles cut to the same depth as 1/16 inch SiC particles in a rotary IMO. I use both. So assuming the particles stay the same size and maintain the same sharpness: Is it better to use a cup of 3/8" particles or a cup of 1/16" particles or even 1/64" particles in say a 12 pound rotary barrel for step 1 ? You would have many many more cutting edges with 1/16" than 3/8" particles for instance. Assume either size cuts to the same depth. On a side note, Step 1 never scratches, it divots. Look at a stone that has come out of a rotary under magnification and you will never find a linear 'scratch'. All material removal is done by 1000's of individual divots. The same type of divots created by a Knoop test. Because rocks in a rotary move relative to each other while the abrasive 'rolls' between the rocks like little ball bearings. This is what causes the divots. Knoop test: Obsidian after step 1 using SiC 30. No scratches, just mass divots: So IMO it is important to know the way rocks are wearing in step 1. Totally not by linear scratches as a grinding wheel cuts, but by a unique mass divot type removal. Sharp SiC particles rolling like tiny ball bearings between relative movement of our target rocks scalloping material away. Similar to lapping operations...we are actually lapping our rocks in the rotary using loose grit. Theory easy to prove, take 2 rocks, wet them, add a bit of coarse SiC between them, and rub them together. The sharp particles grab each surface and roll like tiny ball bearings. The divots left are somewhat similar to the divot a Knoop test leaves... my 1/16" Sic on left, 1/8" in middle and 3/8" on right: And my 1/16"-3/16"-3/8" screening process of bulk Carbolon SC silicon carbide. A much cheaper metallurgical grade of 90% pure SiC from Washington Mills. Love this stuff.
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Post by mohs on Oct 7, 2020 9:11:54 GMT -5
I've wondered about CBN grinding wheels for grinding rocks ? as anyone ever used one for lapidary rough grinding doming? those types of wheels are real popular in the sharpening trade especially for H.S.S lathe tools and such... Like to buy one for an experimental purposes time , money little resources have to stick w/my worn out diamonds for now... Good question Ed. The BC may be way effective on lapidary materials. The individual cutting particles may maintain sharpness better than AO and SIC. It may not be near as brittle as silicon carbide, SiC is real brittle but real sharp. Super sharp is perfect for the low grinding pressures used in lapidary work. There can be a fine line between hardness and toughness or these two properties can dominate abrasion or cutting capability. A good example would be a tungsten carbide cutting tip that possesses enough toughness to cut into steel like it was butter for hours and hold its edge yet it is softer than aluminum oxide. Even diamond can not perform such a task. Thanks for the explanation James You are an alchemist abrasive chemist Really insightful extrapolation and all the good stuff Thought you might enjoy this man’s product page Most likely you already know of it Maybe not ...
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Post by Mel on Oct 7, 2020 10:32:18 GMT -5
I wonder how much faster BC would do a rough grind than SiC in a rotary. Might be cost prohibitive but would time benefit be worth it? Not that time is a major concern with tumbling but interesting to think about. Time is money after all (and I have neither so I guess my point is moot). BC Grinding wheels should be affordable Mel from Yuma & Spokane . Using BC in a vibe is probably affordable since the require small doses of abrasives. But we depend on abrasives breaking down to attain polish... A rotary sure gobbles up lots of abrasives during step 1. Can't see it being affordable for step 1 in the rotary unless the BC could be used over and over. (I could not find it in larger than 180 grit.) This brings up another question to ponder for step 1 in a rotary: What is the best size of abrasive particles to use in step 1 if the particles never broke down and stayed permanently sharp ? It is very possible that diamond abrasives would never get dull or break down during step 1 in a rotary. 3/8 inch SiC particles cut to the same depth as 1/16 inch SiC particles in a rotary IMO. I use both. So assuming the particles stay the same size and maintain the same sharpness: Is it better to use a cup of 3/8" particles or a cup of 1/16" particles or even 1/64" particles in say a 12 pound rotary barrel for step 1 ? You would have many many more cutting edges with 1/16" than 3/8" particles for instance. Assume either size cuts to the same depth. Dang jamesp , your knowledge never fails to amaze! Fascinating to think about diamond vs SiC. I hadn't even considered the diamond staying sharp forever. One would have to know exactly how much abuse it could take before dulling, and how effective it is before you could say which is better. Since it wouldn't create a new grinding edge like SiC, I'd think it would have to be pretty darn effective to justify the cost. Everything wears down at some point but how long would it take to notice any difference is the question. Maybe someone who does high end gem cutting would know. Personally I would go 1/64 based on the simple fact that you have more grains = more edges - more grinding but would it be more slicing, grinding or rolling action? Reality is that a larger grit might be the best option based on how it moves around in the barrel. Maybe down the line I can pick up some BSic and try it out. Diamonds are not this girls best friend...unless they can be reused as grit!
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jamesp
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Post by jamesp on Oct 7, 2020 16:11:08 GMT -5
BC Grinding wheels should be affordable Mel from Yuma & Spokane . Using BC in a vibe is probably affordable since the require small doses of abrasives. But we depend on abrasives breaking down to attain polish... A rotary sure gobbles up lots of abrasives during step 1. Can't see it being affordable for step 1 in the rotary unless the BC could be used over and over. (I could not find it in larger than 180 grit.) This brings up another question to ponder for step 1 in a rotary: What is the best size of abrasive particles to use in step 1 if the particles never broke down and stayed permanently sharp ? It is very possible that diamond abrasives would never get dull or break down during step 1 in a rotary. 3/8 inch SiC particles cut to the same depth as 1/16 inch SiC particles in a rotary IMO. I use both. So assuming the particles stay the same size and maintain the same sharpness: Is it better to use a cup of 3/8" particles or a cup of 1/16" particles or even 1/64" particles in say a 12 pound rotary barrel for step 1 ? You would have many many more cutting edges with 1/16" than 3/8" particles for instance. Assume either size cuts to the same depth. Dang jamesp , your knowledge never fails to amaze! Fascinating to think about diamond vs SiC. I hadn't even considered the diamond staying sharp forever. One would have to know exactly how much abuse it could take before dulling, and how effective it is before you could say which is better. Since it wouldn't create a new grinding edge like SiC, I'd think it would have to be pretty darn effective to justify the cost. Everything wears down at some point but how long would it take to notice any difference is the question. Maybe someone who does high end gem cutting would know. Personally I would go 1/64 based on the simple fact that you have more grains = more edges - more grinding but would it be more slicing, grinding or rolling action? Reality is that a larger grit might be the best option based on how it moves around in the barrel. Maybe down the line I can pick up some BSic and try it out. Diamonds are not this girls best friend...unless they can be reused as grit! The diamond comment tickled me. They always seemed over rated and (ha ha) transparent. Maybe they would make long term reusable grit if they can be captured from the tumbling slurry. Diamonds are Knoop hardness 7000 and quartz is 820. It may be that the quartz would take a very long time to dull the diamonds. Could be a very long time. I totally agree that the smaller abrasives would lend more cutting edges. Since the cutting force in a rotary tumbler is low and the abrasive is removing super shallow amounts each pass. When using the 3/8" silicon carbide it is constantly breaking down into smaller pieces being so brittle, exposing new sharp edges constantly. Like sic 4 to sic 8 to sic 16 to sic 30 to sic 46 to sic 60 etc etc, all of these sizes are effective in step 1. It makes sense that if you start with a big particle it will continue to break down to smaller particles for a longer time than if you started with SiC 80 or 90 for instance. One of those sizes is removing material the quickest, most likely a smaller size with lots of cutting edges. Which size is the best might be a mystery unless some involved tests were run. It would be the best size for diamond it would seem.
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EricD
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Post by EricD on Oct 7, 2020 18:06:23 GMT -5
Dang jamesp , your knowledge never fails to amaze! Fascinating to think about diamond vs SiC. I hadn't even considered the diamond staying sharp forever. One would have to know exactly how much abuse it could take before dulling, and how effective it is before you could say which is better. Since it wouldn't create a new grinding edge like SiC, I'd think it would have to be pretty darn effective to justify the cost. Everything wears down at some point but how long would it take to notice any difference is the question. Maybe someone who does high end gem cutting would know. Personally I would go 1/64 based on the simple fact that you have more grains = more edges - more grinding but would it be more slicing, grinding or rolling action? Reality is that a larger grit might be the best option based on how it moves around in the barrel. Maybe down the line I can pick up some BSic and try it out. Diamonds are not this girls best friend...unless they can be reused as grit! The diamond comment tickled me. They always seemed over rated and (ha ha) transparent. Maybe they would make long term reusable grit if they can be captured from the tumbling slurry. Diamonds are Knoop hardness 7000 and quartz is 820. It may be that the quartz would take a very long time to dull the diamonds. Could be a very long time. I totally agree that the smaller abrasives would lend more cutting edges. Since the cutting force in a rotary tumbler is low and the abrasive is removing super shallow amounts each pass. When using the 3/8" silicon carbide it is constantly breaking down into smaller pieces being so brittle, exposing new sharp edges constantly. Like sic 4 to sic 8 to sic 16 to sic 30 to sic 46 to sic 60 etc etc, all of these sizes are effective in step 1. It makes sense that if you start with a big particle it will continue to break down to smaller particles for a longer time than if you started with SiC 80 or 90 for instance. One of those sizes is removing material the quickest, most likely a smaller size with lots of cutting edges. Which size is the best might be a mystery unless some involved tests were run. It would be the best size for diamond it would seem. I would like to think it's 80, since I just bought 25lbs I wasn't impressed with 46/70 at all, 60/90 worked better, but I didn't record it's material removal abilities. Yet.
All subject to method and ratio and quantities and source and quality and efficiency of grading, also. Maybe even temperature. Definitely the viscosity of the liquid and size of the barrel.
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jamesp
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Post by jamesp on Oct 7, 2020 22:21:30 GMT -5
The diamond comment tickled me. They always seemed over rated and (ha ha) transparent. Maybe they would make long term reusable grit if they can be captured from the tumbling slurry. Diamonds are Knoop hardness 7000 and quartz is 820. It may be that the quartz would take a very long time to dull the diamonds. Could be a very long time. I totally agree that the smaller abrasives would lend more cutting edges. Since the cutting force in a rotary tumbler is low and the abrasive is removing super shallow amounts each pass. When using the 3/8" silicon carbide it is constantly breaking down into smaller pieces being so brittle, exposing new sharp edges constantly. Like sic 4 to sic 8 to sic 16 to sic 30 to sic 46 to sic 60 etc etc, all of these sizes are effective in step 1. It makes sense that if you start with a big particle it will continue to break down to smaller particles for a longer time than if you started with SiC 80 or 90 for instance. One of those sizes is removing material the quickest, most likely a smaller size with lots of cutting edges. Which size is the best might be a mystery unless some involved tests were run. It would be the best size for diamond it would seem. I would like to think it's 80, since I just bought 25lbs I wasn't impressed with 46/70 at all, 60/90 worked better, but I didn't record it's material removal abilities. Yet. All subject to method and ratio and quantities and source and quality and efficiency of grading, also. Maybe even temperature. Definitely the viscosity of the liquid and size of the barrel.
Consider running a measured amount of Mohs 3 calcite in each of say SiC 30-46-60-90 for a week and check weight loss of each. Calcite may not break down silicon carbide as perhaps diamond would hold up against quartz.
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