mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Dec 30, 2017 21:28:25 GMT -5
I know a lady in WY who has maybe 40 barrels of rock, a good portion of which is tumble grade. I thought about making her an offer on all of it (no idea how I would move it), and began to wonder how much it would actually cost to tumble a barrel. I would use five 40 lb lortone rotary units for 60/90 and 600#, then go to a 50lb Viking for 800# and TXP polish. Here are my assumptions; Grit costs per barrel per cycle: 60/90 $2.50/lb. x 4 lbs 600# $4/lb x 4 lbs. 800# $4/lb. x 1/4 lb. (vibe) TXP $7/lb. x 1/4 lb. So 800 lbs rough/40 lbs per load= 20 loads in rotary for 60/90.
I assume a loss of about 30% after rough.=560 lbs. net left for the rest of the cycles. The 600# cycle would then be only 14 loads. Through 600# takes a month (3 weeks + 1 week), so it would take about 4 months total time in the rotaries. This is an important number because of electricity costs.
Without boring you with the math, my total grit costs are; 60/90 $200; 600# $224; 800# $19; TXP $38. So, total grit costs to polish 800 pounds of rough (finishing with 560 lbs) would be %481.
The interesting number is the power costs. At the least, it will cost me $125/month to run those five rotaries. I have done this for a long time, so I know this number is real. These are CA electricity rates. For 4 months, there is another $500. That's probably conservative. Now we are at a total cost of $981 for 560 lbs of finished material.
Transportation costs. Renting a trailer going into CA is cheap. I could rent a trailer cable of carrying two barrels for about $150. I would have to haul the material to CA to process it, the back to Montana to sell it. Trailer costs going out of CA are stupidly expensive, because everyone in their right mind wants out of this state, so probably $300 to haul the stuff out, $450/2= $225 per barrel trans costs. Adding the trans costs, we are at $1206 for 560 ponds of finished material, or about $2.15 per pond.
Obviously missing are the equipment maintenance, the back-breaking labor involved in loading and unloading, lifting a 40 lortone barrel (which weighs 75 lbs. with grit and water) nearly 70 times, and gas. My conclusion is it is illogical to figure you can tumble for less than $3/lb. Which means you need to get at least $6/lb for your stuff. Oh yeah, this assumes she gives me the rock for free! What would you give for a barrel of tumbling material? I know it depends on what it is- lets say Montana moss agate, or west Texas agate or WY petrified wood. A buck a pound for a barrel seem fair? Now you need to get $8/lb. retail.
No wonder they call it a hobby.
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Post by youp50 on Dec 30, 2017 22:02:20 GMT -5
On the outside chance that you would do it, I have a SS basket Maytag commercial washer I could let go cheap. Western Wisconsin. Line the barrel with cutting boards and spray it down with Plastisol...I would load it. A couple hundred a load? Seriously cut down your time and electricity, maybe.
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Post by Jugglerguy on Dec 30, 2017 22:59:03 GMT -5
I tumble for the fun of it, not to make money, so I try not to not think about how much it costs. I’m sure the cost would be depressing. How long do you run your rocks in the first stage? My rocks stay in the first stage until they’re done, which can be anywhere between about three weeks and several months. It sounds like you put your rocks in for a set amount of time, one week maybe?
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mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Dec 30, 2017 23:28:32 GMT -5
Juggler, I run 60/90 for three weeks, then 600 for a week.
I used to do a week at 60/90 one at 220, and one at 400. Then I learned I was wasting a lot of time and muscle when 3 weeks at 60/90 accomplished the same thing.
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,339
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Post by quartz on Dec 30, 2017 23:29:47 GMT -5
mikeinsjc, having supplied a rock shop with finished tumbles for about three years [they went HS on us], I see your numbers as pretty close, we figured $2.75/lb. to tumble in 5 gallon [50 lb.] barrels. Likely a bit higher now a few years later, and I think our Oregon elect. rates of $.05/kwh probably cheaper than yours, $20/mo. for double barrel set. We sold for $6/lb. and the rock shop sold for $10 to $12/lb. They had a good tourist trap location. Have you done a lot of homework on grit costs, I get it at Kleen Blast in Portland, OR and they have stores in CA, might be cheaper for you if fairly local. For your haul-in, would it be practical to get a U-Haul truck and get a bunch at once? Good luck with your project.
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Post by Jugglerguy on Dec 30, 2017 23:44:50 GMT -5
Juggler, I run 60/90 for three weeks, then 600 for a week. I used to do a week at 60/90 one at 220, and one at 400. Then I learned I was wasting a lot of time and muscle when 3 weeks at 60/90 accomplished the same thing. Ok, so you run steady for three weeks with no clean outs or recharges? You’re not going for perfection, but for quantity. I’d love to see what they look like.
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Post by rmf on Dec 31, 2017 8:10:55 GMT -5
I know a lady in WY who has maybe 40 barrels of rock, a good portion of which is tumble grade. I thought about making her an offer on all of it (no idea how I would move it), and began to wonder how much it would actually cost to tumble a barrel. I would use five 40 lb lortone rotary units for 60/90 and 600#, then go to a 50lb Viking for 800# and TXP polish. Here are my assumptions; Grit costs per barrel per cycle: 60/90 $2.50/lb. x 4 lbs 600# $4/lb x 4 lbs. 800# $4/lb. x 1/4 lb. (vibe) TXP $7/lb. x 1/4 lb. So 800 lbs rough/40 lbs per load= 20 loads in rotary for 60/90. I assume a loss of about 30% after rough.=560 lbs. net left for the rest of the cycles. The 600# cycle would then be only 14 loads. Through 600# takes a month (3 weeks + 1 week), so it would take about 4 months total time in the rotaries. This is an important number because of electricity costs. Without boring you with the math, my total grit costs are; 60/90 $200; 600# $224; 800# $19; TXP $38. So, total grit costs to polish 800 pounds of rough (finishing with 560 lbs) would be %481. The interesting number is the power costs. At the least, it will cost me $125/month to run those five rotaries. I have done this for a long time, so I know this number is real. These are CA electricity rates. For 4 months, there is another $500. That's probably conservative. Now we are at a total cost of $981 for 560 lbs of finished material. Transportation costs. Renting a trailer going into CA is cheap. I could rent a trailer cable of carrying two barrels for about $150. I would have to haul the material to CA to process it, the back to Montana to sell it. Trailer costs going out of CA are stupidly expensive, because everyone in their right mind wants out of this state, so probably $300 to haul the stuff out, $450/2= $225 per barrel trans costs. Adding the trans costs, we are at $1206 for 560 ponds of finished material, or about $2.15 per pond. Obviously missing are the equipment maintenance, the back-breaking labor involved in loading and unloading, lifting a 40 lortone barrel (which weighs 75 lbs. with grit and water) nearly 70 times, and gas. My conclusion is it is illogical to figure you can tumble for less than $3/lb. Which means you need to get at least $6/lb for your stuff. Oh yeah, this assumes she gives me the rock for free! What would you give for a barrel of tumbling material? I know it depends on what it is- lets say Montana moss agate, or west Texas agate or WY petrified wood. A buck a pound for a barrel seem fair? Now you need to get $8/lb. retail. No wonder they call it a hobby. From my experience you are right on the money. I have not calculated the cost of tumbling in 10 years but $3/lb was about right (power and is a big variable). Also, your estimate of $8 or $9 for finished stone is about the wholesale cost of commercial tumbled stones depending on the variety. So again on the money. However you may have overlooked one loss. most rocks need to be cracked unless they are already to size. Cracking by hand 800# of rock you will probably loose 5-10% of the original weight. If you use a jaw crusher you will loose 15 to 20% of the weight and if you use a hammermill you may loose 30 to 35% of the original weight in the form of -1/4" material.
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Post by HankRocks on Dec 31, 2017 8:51:32 GMT -5
I would suspect that you would not want to tumble that much rock. There is probably some of that rock that is more valuable as rough for slabs. You would not have to cut slabs, just sell the rough. Quicker return on any investment that is if you consider sorting through 40 barrels quick. You will eventually go through it all anyway so just set aside the the nicer big pieces for cutting. Personally I would have to see any larger Montana, Brazilian, etc type agates broken up for tumbling.
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Post by HankRocks on Dec 31, 2017 8:53:10 GMT -5
correction(I would have hate to see)
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notjustone
spending too much on rocks
Member since January 2017
Posts: 426
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Post by notjustone on Dec 31, 2017 9:29:22 GMT -5
I know a lady in WY who has maybe 40 barrels of rock, a good portion of which is tumble grade. I thought about making her an offer on all of it (no idea how I would move it), and began to wonder how much it would actually cost to tumble a barrel. I would use five 40 lb lortone rotary units for 60/90 and 600#, then go to a 50lb Viking for 800# and TXP polish. Here are my assumptions; Grit costs per barrel per cycle: 60/90 $2.50/lb. x 4 lbs 600# $4/lb x 4 lbs. 800# $4/lb. x 1/4 lb. (vibe) TXP $7/lb. x 1/4 lb. So 800 lbs rough/40 lbs per load= 20 loads in rotary for 60/90. I assume a loss of about 30% after rough.=560 lbs. net left for the rest of the cycles. The 600# cycle would then be only 14 loads. Through 600# takes a month (3 weeks + 1 week), so it would take about 4 months total time in the rotaries. This is an important number because of electricity costs. Without boring you with the math, my total grit costs are; 60/90 $200; 600# $224; 800# $19; TXP $38. So, total grit costs to polish 800 pounds of rough (finishing with 560 lbs) would be %481. The interesting number is the power costs. At the least, it will cost me $125/month to run those five rotaries. I have done this for a long time, so I know this number is real. These are CA electricity rates. For 4 months, there is another $500. That's probably conservative. Now we are at a total cost of $981 for 560 lbs of finished material. Transportation costs. Renting a trailer going into CA is cheap. I could rent a trailer cable of carrying two barrels for about $150. I would have to haul the material to CA to process it, the back to Montana to sell it. Trailer costs going out of CA are stupidly expensive, because everyone in their right mind wants out of this state, so probably $300 to haul the stuff out, $450/2= $225 per barrel trans costs. Adding the trans costs, we are at $1206 for 560 ponds of finished material, or about $2.15 per pond. Obviously missing are the equipment maintenance, the back-breaking labor involved in loading and unloading, lifting a 40 lortone barrel (which weighs 75 lbs. with grit and water) nearly 70 times, and gas. My conclusion is it is illogical to figure you can tumble for less than $3/lb. Which means you need to get at least $6/lb for your stuff. Oh yeah, this assumes she gives me the rock for free! What would you give for a barrel of tumbling material? I know it depends on what it is- lets say Montana moss agate, or west Texas agate or WY petrified wood. A buck a pound for a barrel seem fair? Now you need to get $8/lb. retail. No wonder they call it a hobby. so let me get this straight your gonna tumble 800 lbs of rock and only use 100 lbs coarse grit? (assuming average price for grit at 100 dollars per 50 lbs bag) especially with them hard agates or silified pet wood. sounds like not nearly enough coarse grit to me.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Dec 31, 2017 9:34:10 GMT -5
I am attacking the electricity and coarse grit costs. They well exceed all other costs in my operation. Coarser stage 1 abrasive and higher speeds during coarse along with barrels made to handle these conditions. And a tumbler frame made to handle these conditions. The cost of the tumbler and the barrels is negligible if they are used for years and are reliable. An electric motor does not draw much more electricity spinning barrels at 60 to 80 RPM than at 30 RPM yet grind rate is substantially faster. Then the use of faster cutting cheap bulk SiC is a big money saver.
A given size(6 to 10 inch) barrel spinning at 30 RPM with and aggressive 60% fill verses same barrel at 70 RPM at a gentler 75 to 80% fill isn't as efficient a grinding arrangement. Factory machines are not designed for those speeds for some restrictive reasons, primarily product liability. They don't want the client to grab a 25 pound barrel at 70 RPM for fear of a pinched finger or risk a shirt tail getting caught between barrel and shaft. Can't blame them. Turn machine off before unloading, solves all those safety issues.
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Post by captbob on Dec 31, 2017 9:37:16 GMT -5
I can't see 800 pounds of rock being in a 55 gal barrel. Maybe 800 pounds if the barrel was full of cement, but rocks usually have spaces between them. The larger the rocks, the more empty space. I had 3 full 55 gal barrels of rocks shipped up from Brazil and don't think that any of the barrels weighed more than 500 pounds.
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Post by Drummond Island Rocks on Dec 31, 2017 9:51:22 GMT -5
I did a cost study on a here a few years ago. Rock price is a big variable though. $2 per pound is about the minimum I pay for tumbling rough but lately I would say $6 to $10 per pound (Bahia agate, blue lace agate, lakers, botswana agate, tiger eye etc...). I have learned that tumbling cheap boring rough takes the same amount of grit and labor as tumbling high end stuff so I don't bother with anything that is not appealing to me now. Here is my old write up I thought I would share my process for getting 3 pounds of polished rocks every week. I really enjoy tumbling rocks but due to my impatience I needed to come up with a way to get more rocks completed in a shorter amount of time. To accomplish this I found the key to the whole thing was to have enough rocks rolling in stage one so that during my weekly cleanouts I could pull 3-4 pounds out that were pit free and flaw free to be set aside for stage two. So far I have found that having 20-30 pounds of rock in stage one (46-70) at all times allows me to do this so I run a 12 pound Lortone and a homemade tumbler running as many as eight 3 pound Lortone barrels. The next step was to figure out how to process the rocks through the next 5 stages in a 7 day window. This is where the lot-o vibrating tumbler comes in handy. Here’s an example of stage 2-6 being done in 7 days. Saturday - 12:00pm put 3-4 pounds of rock in S/C 120/220 (two tablespoon / borax only with soft rocks) Sunday - 8:00pm clean out and switch to A/O 500 (1/2 teaspoon / one tablespoon borax and ceramics) Monday - 8:00pm clean out and switch to A/O 1000 (1/2 teaspoon / one tablespoon borax and ceramics) Tuesday Wednesday - 8:00 clean out and switch to A/O polish (1/2 teaspoon / one tablespoon borax and ceramics) Thursday Friday Saturday - 8:00am cleanout and switch to two tablespoons of borax and ceramics for burnish Saturday - 12:00pm rocks complete Now here comes that bad part. trying to figure out how much time and money is involved? Here are my rough weekly estimates. 3 hours labor per week for clean outs (minimum, I think I spend more then this) $6 per week in grits and polish $5 per week electricity for the tumblers The value of the rough rocks is hard to figure but even at $2.50 per pound that’s still about $10 per week So after looking at all of this I guess you could say I have about 3 hours labor and $20 out of pocket each week to get 3-4 pounds of nice shiny rocks. I almost forgot equipment costs. I got great deals on some of my stuff but if it were all purchased new the cost would be over $700 just for the tumblers so even if I have been tumbling for 2 years that’s still as much as $7.00 per week for the equipment. This is just an estimate and things vary each week but I think this paints a pretty good picture of what a week of rock tumbling looks like around my house right now. Read more: forum.rocktumblinghobby.com/thread/61075/pounds-polished-rocks-week-costs#ixzz52ql1McT8Chuck
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Post by bobby1 on Dec 31, 2017 12:26:00 GMT -5
I run my tumblers with 60 grit for a month, empty the barrel, wash it out and run in polish for a month (sometimes 5 weeks in polish). Works great with a great polish on the rocks. This has been my method for the last 30 years of tumbling. I run a 40lb unit and two 12 lb units. I mostly tumble the rocks for our show's wheel of fortune. Bob
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mikeinsjc
spending too much on rocks
Member since June 2010
Posts: 329
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Post by mikeinsjc on Jan 2, 2018 1:08:20 GMT -5
notjuststone, Well, let me recalculate on the rough grit. I figured 800 lbs is 20 tumblers full of rough (using the 40 lb units). Each run uses 5 cups= 4 lbs of 60/90. Twenty runs x 4lbs= 80 lbs.
captnbob, I really have no idea on the weight of a barrel, that was just a guess. I think you are closer to right than I am though, now that I think about it, cuz a 5 gal bucket weights what maybe 50-60 lbs? Times 11 puts it closer to your estimate than mine. Have to recalc the cost now.
jugglerguy, Right, no cleanouts or recharges, three weeks straight. I haven't found that to make any difference in final quality. But I used to be less than pleased when I did all the cycles thru polish in the rotaries. I was having to redo a lot of pieces. All that changed when I went to the big 50 lb Viking vibe for 800 prepolish and final polish. I think the aggressive action of the Viking covers some of my sins! My final polish is as good as any I have seen. Except for obsidian. It hates me.
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SirRoxalot
freely admits to licking rocks
Member since October 2003
Posts: 790
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Post by SirRoxalot on Feb 17, 2018 14:13:59 GMT -5
I wouldn't hesitate to buy it all for a buck a pound, if it's good colorful stuff, that's just good fun.
As for costs, well, at that amount of rock it's hardly a hobby. Handling and transporting cost, meh, that's what we do, gotta have a truck or a trailer.
If the cost of it all seems prohibitive to you, here's some comparisons from other areas in the gem and mineral world.
Nowadays a fine, colorful, undamaged mineral specimen can go for $10,000. Easily. At Tucson, lots are that price, some are a quarter million, some are over a million these days.
If a few grand is a major stumbling block, don't get into faceting, where the machine alone can be $2,000 for the bare minimum! And if you want to cut something nice, like tanzanite, well, that can be hundreds per carat... and you grind away 80% of that.
One good point is that the rock is on the continent. Importing from Africa can double the price, then you've got taxes, duty, customs... oy vey.
Another way of thinking about it: you can sell every nicely polished tumbled stone for $1 to $10 each. Lot of stones in a barrel...
So it's all relative.
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