gatorflash1
spending too much on rocks
Active in Delaware Mineralogical Society, Cabchon Grinding and Polishing, 2 Thumlers B's and a UV-18
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Post by gatorflash1 on Jan 11, 2019 20:17:46 GMT -5
Since the grit breaks down during the tumbling I'm wondering if 60 grit is all I need for stage 1. I'm thinking after ten days of tumbling I am probably using 90 grit (from the broken down 60 grit). Thoughts?
Is there really any reason to use a two part grit at any stage or can you just go with the largest recommended grit?
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Post by Drummond Island Rocks on Jan 11, 2019 20:30:45 GMT -5
Some of the reasoning is availability. I have not seen graded 60 grit advertised at the rock shed or kingsley north. I have tried graded 80 grit for stage one and did not like it. Stage one grit also depends on barrel diameter. Larger diameter barrels break down grit more effectively. 60/90 works good in lortone 3 pound barrels and 46/70 works good in lortone 6 and 12 pound barrels. With the 46/70 much like the 60 in 60/90 the 46 is not sold in graded. The mixture of sizes work pretty well together.
Edit: I do see graded 60 at Kingsley north. Could be worth a try. As long as no unspent grit is seen during your clean outs then it should be fine.
Chuck
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El JeffA
spending too much on rocks
Member since February 2016
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Post by El JeffA on Jan 11, 2019 22:17:42 GMT -5
My thoughts. I’m sure you know and was just a mistake in original post, that using “90 grit broken down to 60” is backward. The larger the number, the smaller the grit. I have used as large as 30 grit but it really takes a toll on the Lortone and Thumler tumblers...especially the lid liners...but he bottoms also. I am happy using 46/70 in the 15 lb Thumlers and 12 pound Lortones for the rough grind. I also have a couple Lortone 33B’s but won’t run anything larger than 60/90 in them. The smaller barrels just don’t break it down like the bigger barrels. My cleanouts are once a week. After 1 week, the 46/70 is broken down to a fine powder (less than 120/220) in the larger tumblers. The 2 numbered grit means that there is a wider variance in separation of sizes. The 60/90 means that sizes from 60 through 90 can be present. Size 60 (or any other single size) grit means that more strict methods are used to assure only size 60 grit is present. Usually, stricter standards require more sorting, more time and thus higher cost. If there is no cost difference, then it really just comes down to what you prefer or feel comfortable with. I experimented and have arrived at what ‘I’ like and feel gives me the best results for me. I hope this helps...and fun with it.
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kskid
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Post by kskid on Jan 11, 2019 22:59:04 GMT -5
For another perspective, I use 36 SiC from the rock shed in my QT6 and now QT12. I prefer it because I typically go two weeks between cleanouts, which gives it plenty of time to break down. It does wear on the barrel and lid, but I got over 3 years of continuous running on the last lid.
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Post by As I in does tries! on Jan 12, 2019 5:07:21 GMT -5
Grits really depends where your are in the world, on the North American continent split grits are cheaper, elsewhere fixed grits are cheaper and split grits may not be available whatsoever, for example. In the United Kingdom I can get 25kg(55lb) bag of Fixed 80 grit Silicon Carbide for £80 ($100). I can order 25kg(55lb) bag of 60/90 Silicon Carbide grit direct from the importer for £120 ($148). I can order 25kg(55lb) bag of F80 Aluminum Oxide grit direct from the importer for £160 ($200). I can order 25kg(55lb) bag of F220 Aluminum Oxide grit direct from the importer for £200 ($248). I cannot buy 500 or finer Aluminum Oxide grit including polish without importing myself costing 6 - 10 times the cost depending on how much in weight and money. Rockshed: 1 Pound of Rock Shed's AO polish = $4.75, postage to UK = $23.50, total = $28.25 + Import duty 20% + $10 Import fee = $43.90. 5 pounds of Rock Shed's AO polish = $20.00, postage to UK = $71.65, total = $91.65 + Import duty 20% + $10 Import fee = $119.98. 4.5 inch diameter barrel work (Lortone 1.5lb/2lb/3lb) 45 grit but at increased wear and tear (F80 or 60/90). 8 inch diameter barrel work (Lortone QT6/QT/QT66/QT12) 35 grit but at increased wear and tear (F80 or 60/90). I tried F20 grit with Lortone C300 Qt66 and QT12 barrels with virtually no grinding whatsoever, after 14 days the grit was still unbroken! The bigger the barrel the more grit you use the faster it grinds, the more it costs $$$! Aussie Lapidary Forum: Rock Tumbling Guide!
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doublet83
starting to spend too much on rocks
Member since March 2016
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Post by doublet83 on Jan 12, 2019 13:23:16 GMT -5
Some of the reasoning is availability. I have not seen graded 60 grit advertised at the rock shed or kingsley north. I have tried graded 80 grit for stage one and did not like it. Stage one grit also depends on barrel diameter. Larger diameter barrels break down grit more effectively. 60/90 works good in lortone 3 pound barrels and 46/70 works good in lortone 6 and 12 pound barrels. With the 46/70 much like the 60 in 60/90 the 46 is not sold in graded. The mixture of sizes work pretty well together. Edit: I do see graded 60 at Kingsley north. Could be worth a try. As long as no unspent grit is seen during your clean outs then it should be fine. Chuck Chuck, can you elaborate why you didn't like the graded 80 grit?
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Post by Drummond Island Rocks on Jan 12, 2019 13:57:52 GMT -5
Some of the reasoning is availability. I have not seen graded 60 grit advertised at the rock shed or kingsley north. I have tried graded 80 grit for stage one and did not like it. Stage one grit also depends on barrel diameter. Larger diameter barrels break down grit more effectively. 60/90 works good in lortone 3 pound barrels and 46/70 works good in lortone 6 and 12 pound barrels. With the 46/70 much like the 60 in 60/90 the 46 is not sold in graded. The mixture of sizes work pretty well together. Edit: I do see graded 60 at Kingsley north. Could be worth a try. As long as no unspent grit is seen during your clean outs then it should be fine. Chuck Chuck, can you elaborate why you didn't like the graded 80 grit? A couple years ago Kingsley had a good sale on 50 pounds of graded 80 grit. A few of us that were using 60/90 at the time gave the graded 80 a try. It just did not have the cutting power that the 60/90 mix has. I ended up slowly mixing the 80 grit into my 60/90 just to get rid of it. Chuck
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jamesp
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Post by jamesp on Jan 13, 2019 4:42:05 GMT -5
step 1 at the House of Hell. These thick wear proof barrels hold a total of 90 pounds and rotate at 85 RPM. Dedicated to shaping. Home made machine and barrels. Washington Mills bulk SiC at 45 cents per pound not screened. Manually screened as purchased in 50 pound bags: SiC 30 and smaller at left, SiC 4,8,16 in middle, SiC 2,1 0, 00, 000 at right all run as a mix in step 1. Homemade machine and barrels paid off in about 2 years in abrasive and electricity savings. Big time saver too as it only runs 6 months out of the year for the same production with finer grit and slower speed in a year. Absolutely the best tumbling investment I ever made.
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gatorflash1
spending too much on rocks
Active in Delaware Mineralogical Society, Cabchon Grinding and Polishing, 2 Thumlers B's and a UV-18
Member since October 2018
Posts: 375
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Post by gatorflash1 on Jan 13, 2019 11:19:43 GMT -5
My thoughts. I’m sure you know and was just a mistake in original post, that using “90 grit broken down to 60” is backward. The larger the number, the smaller the grit. I have used as large as 30 grit but it really takes a toll on the Lortone and Thumler tumblers...especially the lid liners...but he bottoms also. I am happy using 46/70 in the 15 lb Thumlers and 12 pound Lortones for the rough grind. I also have a couple Lortone 33B’s but won’t run anything larger than 60/90 in them. The smaller barrels just don’t break it down like the bigger barrels. My cleanouts are once a week. After 1 week, the 46/70 is broken down to a fine powder (less than 120/220) in the larger tumblers. The 2 numbered grit means that there is a wider variance in separation of sizes. The 60/90 means that sizes from 60 through 90 can be present. Size 60 (or any other single size) grit means that more strict methods are used to assure only size 60 grit is present. Usually, stricter standards require more sorting, more time and thus higher cost. If there is no cost difference, then it really just comes down to what you prefer or feel comfortable with. I experimented and have arrived at what ‘I’ like and feel gives me the best results for me. I hope this helps...and fun with it. Thanks for all the good comments. I'm using a 15 lb barrel. What I tried to say in my original post was that after 10 days I'm thinking that my 60 grit was now probably broken down to about size 90 grit. If this is the case I see no reason to buy and start with 60/90 which probably ends up about 90/150+ after 10 days of tumbling and thus wasting time and efficiency in the course grit stage 1 grinding process. In stage one I want the best cutting and fastest course grinding I can get before moving onto stage 2. I don't know if starting with size 35 grit is as efficient as starting with size 60 as 35 is really course stuff but if grinds agate, etc. more quickly than 60 grit I would surely have to try it out. Does this make sense to you? I buy grit in 25 kg bags.
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Post by HankRocks on Jan 13, 2019 17:29:54 GMT -5
My thoughts. I’m sure you know and was just a mistake in original post, that using “90 grit broken down to 60” is backward. The larger the number, the smaller the grit. I have used as large as 30 grit but it really takes a toll on the Lortone and Thumler tumblers...especially the lid liners...but he bottoms also. I am happy using 46/70 in the 15 lb Thumlers and 12 pound Lortones for the rough grind. I also have a couple Lortone 33B’s but won’t run anything larger than 60/90 in them. The smaller barrels just don’t break it down like the bigger barrels. My cleanouts are once a week. After 1 week, the 46/70 is broken down to a fine powder (less than 120/220) in the larger tumblers. The 2 numbered grit means that there is a wider variance in separation of sizes. The 60/90 means that sizes from 60 through 90 can be present. Size 60 (or any other single size) grit means that more strict methods are used to assure only size 60 grit is present. Usually, stricter standards require more sorting, more time and thus higher cost. If there is no cost difference, then it really just comes down to what you prefer or feel comfortable with. I experimented and have arrived at what ‘I’ like and feel gives me the best results for me. I hope this helps...and fun with it. Thanks for all the good comments. I'm using a 15 lb barrel. What I tried to say in my original post was that after 10 days I'm thinking that my 60 grit was now probably broken down to about size 90 grit. If this is the case I see no reason to buy and start with 60/90 which probably ends up about 90/150+ after 10 days of tumbling and thus wasting time and efficiency in the course grit stage 1 grinding process. In stage one I want the best cutting and fastest course grinding I can get before moving onto stage 2. I don't know if starting with size 35 grit is as efficient as starting with size 60 as 35 is really course stuff but if grinds agate, etc. more quickly than 60 grit I would surely have to try it out. Does this make sense to you? I buy grit in 25 kg bags. depending on how much grit you put in the 15 lb barrel, you will probably find that after 10 days the grit will be reduced to 220 and even finer. I use 46/70 and after 10 days with a couple of recharges, I don't see anything that's coarser than 220. It's all a factor of speed of barrel, fill of barrel, size of rocks. When I run a load of slabs and preforms the breakdown rate is much slower than a load of well rounded river rocks with a few large. For the slabs/preforms I start with 80.
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Post by As I in does tries! on Jan 14, 2019 5:58:51 GMT -5
Greetings according to my own research grit breaks down 25% every 16 hours for the 1st 3 break downs, each break down there after increases by 4 hours for each as the grit is becoming less effective and locked in mud
F80 grit at 0 Hours in Lortone QT12 barrel 80 grit / 4 = 20: 1st break down 16 Hours: 16 Hours 100 grit / 4 = 25: 2nd break down 32 Hours: 16 Hours 125 grit / 4 = 31.25: 3rd break down 48 hours: 16 Hours 156 grit / 4 = 39: 4th break down 68 Hours: 20 Hours 195 grit / 4 = 48.75: 5th break down 92 Hours: 24 Hours 244 grit / 4 = 61: 6th break down 120 Hours: 28 Hours 305 grit / 4 = 76.25: 7th break down 152 Hours: 32 Hours 381 grit / 4 = 95.3125: 8th break down 188 Hours: 36 Hours 476 grit / 4 = 119: 9th break down 228 Hours: 40 Hours 595 grit / 4 = 148.75: 10thth break down 272 Hours = 11 days 8 hours 744 grit 11th break down
[jamesp] also done his own research that is published here of RTH Forums of grit break down!
The best transaction I ever made was a 25kg(55lb) bag of F80 Silicon Carbide grit in 2009 for £57.44($78) about £2.30($3.10) per Kg(2.2lb), still have about 8kg(17.6lb) left today!
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jamesp
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Member since October 2012
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Post by jamesp on Jan 14, 2019 7:18:39 GMT -5
In welding school they taught bearing down on a hand grinder to hasten material removal. Granted the grinding wheel may wear 10 times faster but your grinding job is done 10 times faster. If you use the same principle during coarse grind in a rotary you will get faster material removal also. Just like the grinding wheels the coarse SiC will breakdown much faster and your rocks will shape faster. The easiest way to increase the grinding force in a rotary is using a sticky slurry to suck the rocks together while they tumble. Not a thick slurry, but a sticky slurry. The most common sticky slurry used in industry is sold as an additive and is a basic colloidal clay based slurry. Not only does it make the rocks stick to each as they slide against each other but it also lubricates them. Increasing barrel speed and size helps speed grit breakdown but sticky slurry trumps all in getting efficient grinding because it increases grinding force 24/7. SiC 30 after 14 hours @30rpm using raw colloidal clay additive. Before on right, after on left: A closer view of the SiC 30 after 14 hours @30rpm. Over half the original dose was too small to recover and not effective for coarse grind anyway: Virgin SiC 30 on right, after 14 hours on left: These are the screening and clean water washing steps used to carefully extract the used SiC 30 after 14 hours. Also photographed is the collection of raw colloidal clay slurry from the back yard. The life of the SiC 30 @30rpm was repetitively less than 48 hours using the clay in many many runs. www.flickr.com/photos/67205364@N06/26664907670/in/album-72157677229423944/The Parable of the sower came to mind after this basic discovery. Damn I was proud of myself. Still using the clay during coarse grind. Big game changer.
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jamesp
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Member since October 2012
Posts: 36,154
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Post by jamesp on Jan 14, 2019 7:26:59 GMT -5
A clay based slurry additive by the Covington (lapidary) Engineering bunch.
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Post by johnjsgems on Jan 14, 2019 11:42:25 GMT -5
Back in the day, 60/90 was called "80 ungraded" and was a mix of particles from 60-90 averaging 80. Depending on how much grit is coarser than 80, the 60/90 should be faster than graded 80. In USA mixed grades are generally a little less expensive. As shipping costs are high buying as large a quantity as you can reduces price per lb. As mentioned, coarse grits will grind rocks faster but can cost more in barrel component wear. The best thing you can have when tumbling is patience. The fastest tumbling report I read was a guy that recharged coarse grit every three days. For shaping, the grit was broken down enough to slow results after 3 days. You would need a lot of grit or use the 3 day old grit for subsequent steps.
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Post by greig on Jan 14, 2019 15:52:05 GMT -5
This is a fabulous thread, with great knowledge being shared. I need to pay more attention when I tumble to see what is going on with the grits...or just go back and read the advice here. LOL
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gatorflash1
spending too much on rocks
Active in Delaware Mineralogical Society, Cabchon Grinding and Polishing, 2 Thumlers B's and a UV-18
Member since October 2018
Posts: 375
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Post by gatorflash1 on Jan 15, 2019 20:11:24 GMT -5
Does anybody know if all brands of SIC grits break down at the same rate, all other things being equal? Or is there a certain type or brand that is tougher and lasts longer than others? I'm surprised that as hard as SIC is that it breaks down so fast as shown in "As I In Does Tries" post.
Same question for AO, all equal?
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Post by aDave on Jan 15, 2019 21:08:01 GMT -5
Does anybody know if all brands of SIC grits break down at the same rate, all other things being equal? Or is there a certain type or brand that is tougher and lasts longer than others? I'm surprised that as hard as SIC is that it breaks down so fast as shown in "As I In Does Tries" post. Same question for AO, all equal? Quite frankly, I think you're beginning to get in the weeds. I have never worried about what "brand" grit I am using. If you have the ability to sort things out by "brand," I'd love to see that. However, I think you're splitting hairs. I'll offer advice purely on the way I buy grit. If I'm looking to buy a certain size, I buy it. "Brand" means nothing. That's just me.
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Post by As I in does tries! on Jan 16, 2019 8:09:33 GMT -5
Here in Scotland the average outside temperature was around 10°C(50°F) - 15°C(59°F) when the test was done, the Lortone C300's 1/3hp motor heats up to 75°C(167°F) after 24 hours the barrels around 40°C(104F).
Higher temperatures causes grit break down faster, just having loose grit exposed in hot midday sun, not even in a tumbler, can cause grit to explode, both Aluminum Oxide and Silicon Carbide are affected.
Aluminum Oxide grit breaks a maximum of 25% - 50% then the core of grain start's to act like polish!
Brand of grit is meaning less, there are different types of Aluminum Oxide and Silicon Carbide for many different applications such as grit and powered glue and hardener, you pour it in a mold, seal the mold, cook it the glue melts, cool it the glue hardens, remove from mold and you have either grinding stone block or grinding wheel, Green SC for grinding hardened metal or Black fixed or split grain SC for grinding stone.
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Post by johnjsgems on Jan 16, 2019 18:59:28 GMT -5
Brands no but if you can find green SC it is harder than the black. Aluminum Oxide is mostly used in finer grits as it breaks down to a fine powder. SC breaks down but somehow stays sharp so generally better for tumbling. AO is generally cheaper so it is often used as the fine (600) step in grit kits.
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jamesp
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Post by jamesp on Jan 20, 2019 12:01:30 GMT -5
Most of the silicon carbide made in the US is made and distributed by Washington Mills. Their big manufacturing operation may continue to run at the town of Niagra Falls perhaps because of cheap cost of electricity. Some may sell SiC made overseas. I have never noticed much difference in grey, white or brown aluminum oxide. Having used all 3 colors of AO 80 and AO 220 many times over the years they seem to perform almost exactly the same. Tumbling pretty much reduces each grade in the same amount of tumbling time given other variables staying constant regardless of color. Or grade(not size) such as sand blasting grade or precision single grit grades. Washington Mills making SiC. They sell much cheaper bulk coarser grades for melting into steel for special steel formulations. They make it and leave it outside in large fields till they refine it. Apparently 90% pure before refining. It is not much more than man made dirt. Like silica sand and petroleum melted together. I like tumbling with raw(3/8" and smaller) at 40 cents per pound. Requires purchasing in bulk and best used with rugged barrels. pubs.acs.org/cen/science/87/8730sci1a.html
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