meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 1, 2011 13:29:27 GMT -5
I have been searching for really fine silicon carbide grit to use after the 600 grit step and before the polish step. I have found the following grits:
1000 1200 1500
The best deals I have found on each of them is around $10-$12 a pound.
Does anyone know of a better deal?
Also, can you go from 600 grit to 1500 grit?
:-) Dave
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Post by jakesrocks on Nov 1, 2011 13:41:19 GMT -5
The price sounds good.
After 600 grit, you can cut the amount of grit per load in half, so unless you have a huge tumbler, a pound should last for a few loads.
Normal pre-polish is awfully fine, so I don't see a reason why you couldn, go straight to 1500 SC.
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Post by johnjsgems on Nov 1, 2011 14:08:01 GMT -5
Triploi is a much less expensive pre polish. By the time 600 is broken down you would be very fine anyway.
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Post by johnjsgems on Nov 1, 2011 15:06:21 GMT -5
By the way, aluminum oxide grit in the pre polish range (1000, 1200, etc.) are more common and likely less expensive than SC. Still more than tripoli though.
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meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 1, 2011 15:51:06 GMT -5
John,
Do you happen to know the grit/mesh size of Tripoli?
Dave
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Post by johnjsgems on Nov 1, 2011 21:11:04 GMT -5
No idea. It is a really good pre polish and will even polish some materials.
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snuffy
Cave Dweller
Member since May 2009
Posts: 4,319
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Post by snuffy on Nov 1, 2011 21:34:50 GMT -5
I just checked, Tripoli is $3.50 a lb at therockshed. I've never tried it.
snuffy
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Post by jakesrocks on Nov 1, 2011 23:06:40 GMT -5
Tripoli is more commonly used for metal polish, and in finishing fine furniture. What I've found on the internet says to sand to 1200 grit before using tripoli. This was for finishing furniture, but I suspect the same would apply to finishing rocks.
It would also be wise to read the MSDS sheet on tripoli powders. The dust over time can lead to silicosis.
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meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 7, 2011 11:57:24 GMT -5
Jake,
You said that after 600 you can cut the amount of grit in half. Why is that? And does that include all grits, pre-polishes and polishes that are higher/finer than 600?
This surprises me because the Lortone chart for the amounts of grit to use has a larger amount for 600 and for polish.
Dave
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Post by johnjsgems on Nov 7, 2011 13:59:44 GMT -5
The amount of polish needed depends mostly on quality of polish.
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Nov 7, 2011 14:12:17 GMT -5
Dave, Ignore the charts and instructions for tumbling provided by the tumbler manufacturers. Be leery of most of the advice you might find anywhere else... but here. Recommendations found here are the product of many combined decades of shared experience. Nothing else compares to that.
johnsgems, By quality of polish, are you referring to the uniformity of grit size? Is too much of the volume too fine a grit (to remove "scratches" left after the pre-polish), or does low quality polish contain too many impurities that aren't polish? Or what?
ADDED: Anyone -- why is it low quality polish takes for ever to work, if it does at all?
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meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 7, 2011 14:23:42 GMT -5
Daniel,
I wholehartedly agree with what you said.
So what is the recommended amounts of the various grit sizes (and polishes) per pound of rock that you are tumbling? (if there already is a post covering this, please refer me to it)
Thanks, Dave
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Nov 7, 2011 14:37:33 GMT -5
Dave,
Start with the recommendations given in the pdf doucment provided in the Rotary Tutorial "sticky" at the top of this forum. I think the first link might be a dead end, but the second link will let you download the document.
Daniel
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meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 7, 2011 15:30:40 GMT -5
I just read that chart and it looks like the amounts of grit is the same for stages 1-3 and the amount for polishes is more than that.
Jake, when using 1200 or 1500 Silicon Carbide or Aluminum oxide (or when using Tripoli), do you mean to use 1/2 the amount that they recommend for the grits in stages 1-3 or half the amount they recommend for the polishes?
Dave
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Post by connrock on Nov 8, 2011 9:33:07 GMT -5
Dave,,, Something to remember is that grit breaks down into 1/2 it's original size after 7-10 days in a rotary and about the same in 12-24 hours in a vibe unit.
In a week to 10 days your 600 grit has broken down to about a 1200 grit so your rocks have actually been in a "pre-polish" stage for a short time.
Although I haven't used a rotary tumbler after the rough stage in many ears(I use a vibe unit),,,when I did use one I just let the load run for 2 weeks (or more) in a 600 grit.
For what it's worth,,,, After many years of feeding my rotary tumblers with huge amounts of grit and polish,I started using a Lot-O-Tumbler which is a vibe unit. Starting at the 600 grit stage I only use 1/2 teaspoon full of grit for every 4-1/2 lbs of rocks. Same amount for Tripoli and final polish. Huge savings and each stage only has to run for about 48 hours instead of the weeks it takes in a rotary tumbler.
To be honest with you,,,,,now that I'm retired and living on a pension I couldn't afford to run my rotary tumblers after the rough stage as it would just cost too much for the grit and polish. I get some fairly good results too.
connrock
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meta7
starting to spend too much on rocks
Member since June 2010
Posts: 164
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Post by meta7 on Nov 8, 2011 22:29:10 GMT -5
Connrock,
If 600 breaks down to 1200 after 7-10 days, will it be broken down to approx. 2400 after 14-20 days?
Is there a point where Silicon Carbide stops breaking down?
Dave
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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Post by Steve on Nov 8, 2011 23:03:03 GMT -5
Start a barrel with rounded beach rocks charged with 60/90 and let it run for > 6 months or so. You'll get an ok but not great polish.
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Post by jakesrocks on Nov 8, 2011 23:06:50 GMT -5
I should imagine that given enough time, 600 grit would continue to break down. My last 15lb load ran for about 7 weeks non stop with 60/90 grit. When I cleaned the load it looked like it had just come out of pre-polish. However, I don't know if SC would ever break down enough to give you a polish.
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Post by connrock on Nov 9, 2011 12:14:22 GMT -5
Dave,,, I,like others here don't know if SC will ever break down to a "polish" but I do know that when I run my 1000 SC grit stage for 2 days and then add Tripoli I get results like this with Brazilian Agate and a LOT of other hard rocks,,,,, I like to ask the question,,,,,"Which one was in polish and which one wasn't?" The answer is ,,,,neither! So,,,,,I guess what I'm trying to say is that the 1000 SC breaks down enough for the Tripoli to give one heck of a shine. These rocks were done in my vibe unit. connrock
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