alanc
off to a rocking start
Member since January 2004
Posts: 12
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Post by alanc on Jan 21, 2004 9:12:28 GMT -5
Sounds like coarse grit loses most of its abrasiveness after a week. If you kept it tumbling for a month without recharging, would there be much difference from the result after 7 days?
Are the finer grits the same way?
Does graded or ungraded work best?
Assuming you're going to use cerium oxide for the polish, does it help much to get into the 500 or 800 grit range, or is that overkill?
I'm pumped. This weekend I'm going to make 4 drums out of 4-inch plumbing pipe and maybe next week, an in-line 4-barrel tumbler (on the Thumler concept). If it doesn't explode, I'll post some pictures.
Alan
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James
freely admits to licking rocks
Member since October 2003
Posts: 876
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Post by James on Jan 21, 2004 14:44:15 GMT -5
The grit become less abrassive over time. After a week the 80 grit usually breaks down. So in order to get faster results, you must recharge the grit. If you let it go longer, it will serve as a fine grit and wont grind down the rocks as much. Some poeple do this to save money and skip the 220 stage altogether. I wouldn't recommend this however, because the grit somtimes becomes lodged in crevices in the barrel and can become dislodge contaminating the load.
Think of it like this. You start with 80 grit. After 1 week it breaks down into 120 grit. Then after another week it breaks down into 220 grit and after 1 more week it beaks down into 400 grit and so on... This isn't exact but it should give you an idea of what's going on.
To answer your second question; Ungraded grit is cheaper. That is the only significant difference I've found. Go with 60-90 grit.
As far as a prepolish goes. I use 400 grit and It always works just fine. I have in the past used 600 grit but it dosen't really matter all that much. If you're polishing obsidian, I'd recommend a second 1000 prepolish step befor polish. But this isn't always necessary either. You can still go perfect result just by letting the polish go for an extra week.
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valard
off to a rocking start
Member since October 2003
Posts: 13
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Post by valard on Jan 22, 2004 9:43:38 GMT -5
James stated: "Think of it like this. You start with 80 grit. After 1 week it breaks down into 120 grit. Then after another week it breaks down into 220 grit and after 1 more week it beaks down into 400 grit and so on... This isn't exact but it should give you an idea of what's going on."
That is the same theory espoused by the folks at the Rock Shop I frequent. However, I don't seem to get nearly as good a result by just leaving coarse grit to break down into medium and fine. (They have suggested I do this on several occasions) It is a lot more work, but I seem to get significantly better results by cleaning out the barrel after one week of coarse and using medium, then fine.
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hurk
starting to shine!
Member since March 2003
Posts: 37
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Post by hurk on Jan 22, 2004 15:07:16 GMT -5
I have Been tumbling for a year now and from help from others of this board during the first stage it is wise to reload course grit as soon as 3-4 days for the grit has broken down that quickly in alot of cases... after all stage 1 is for shapeing the stones and you want to do this as quickly as possible and rough grit is reasonably priced compared to polish If i am wrong here someone straighten me out HURK
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James
freely admits to licking rocks
Member since October 2003
Posts: 876
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Post by James on Jan 22, 2004 19:28:41 GMT -5
Let the 80 grit for for 7 days. You'd be surprised at how much it still works even after 4-5 days of tumbling. I did an experiment. I let a berrel go for 5 days. I then cleaned it out and let the grit settle in the bottom of a bucket to see how much of the grit was actually left. I found a nice thick layer remaining in the bottom. I then let another berrel go for a full 8 days. The first thing I noticed was how much more matieral had been eroded away. The slurry was thick and the grit had broken down to a point that little had settled in the bottom of the bucket. Just be patient. The grit is still working even if you can't see it.
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