Pre-grit rough tumble ¿

captbob
no longer being taken for granite

St. Pete FL

Member since December 2007
Posts: 8,186

Pre-grit rough tumble ¿ Mar 1, 2008 10:21:34 GMT -5

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Post by captbob on Mar 1, 2008 10:21:34 GMT -5

Just throwing this thought out for comments...

It seems that many hammer their rocks to make them tumbler size. This has to produce some very jagged edges and shapes that are meant to be removed by the tumbling process.

I was wondering how much of this shaping is simply due to the tumbling action and to what extent the coarse grit actually aids in this initial stage. Yes, I understand that the grit will be necessary eventually, but I'm curious if it is being wasted at the start.

I haven't tried this yet because I'm still a tumbling "newbie" and want to see some results without adding extra time to the process, but...

has anyone ever experimented with doing a rough tumble (for a week or more) with no grit at all to see what happens to the rock shapes?

I'm sure the grit sellers wouldn't appreciate if it were found that grit isn't needed in the initial shaping of rough rocks, and I'm equally sure that if this (no grit) worked then I would have read about it.

So, has anyone tried this to see what the tumbling action alone does to shape the rocks? I know I'll give it a shot someday just for grins, but thought I'd ask here.

Bottom line question I guess is: would a week, or whatever, pre-tumble save you a grit recharge (maybe more?) OR would it be a waste of time?

< font = way too much free time >

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darrad
fully equipped rock polisher

Member since September 2006
Posts: 1,636

Pre-grit rough tumble ¿ Mar 1, 2008 11:58:11 GMT -5

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Post by darrad on Mar 1, 2008 11:58:11 GMT -5

Interesting thought. I do hammer some rock and of course there are very sharp edges and have wondered if it is chewing up the rubber on the inside of my barrels.
What about taking a bunch of hammered stuff and putting in a cement mixer, One of those smaller ones like they have at Harbor Freight. Add some water and let it go 24 hours or so. Sounds to me like you may be on to something here. Hmmm.......

Dave

geogoddess
spending too much on rocks

Member since December 2007
Posts: 287

Pre-grit rough tumble ¿ Mar 1, 2008 13:05:20 GMT -5

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Post by geogoddess on Mar 1, 2008 13:05:20 GMT -5

I think you'd be better off putting them in a cement mixer than the relatively cushioney tumbler barrels. I'd probably add in some graded sand. You might get some action to knock the edges off... but even when rocks get rounded in a stream bed... there's a grit (sand)... just not the SiC we use.

rockdewd
has rocks in the head

Member since October 2007
Posts: 605

Pre-grit rough tumble ¿ Mar 1, 2008 13:16:24 GMT -5

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Post by rockdewd on Mar 1, 2008 13:16:24 GMT -5

I've done it purely out of absent mindedness. Forgot to add grit after I cleaned out one 6 lb tumbler. I clean out my rotary tumblers every two weeks and two weeks of tumbling without grit only produces slightly discolored water. The rocks are pretty much as they went in.

Rick

cutter
starting to spend too much on rocks

Member since February 2008
Posts: 129

Pre-grit rough tumble ¿ Mar 1, 2008 14:59:51 GMT -5

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Post by cutter on Mar 1, 2008 14:59:51 GMT -5

Howdy all. For what it is worth, An oldtimer I use to know, made a contraption for pre-tumbleing. He had an old tire that hung on a shaft that was driven by a rather small electric motor. He would put all kinds of odd pieces large and small in it with regular course river sand in it with a few inches of water. This thing ran all the time. Even deep into our freezing winters. Whenever he had a tumbler freed up, he would sort out the pieces he deamed ready to roll. I have seen setups using mutiple tires that as they smooth out you can moove them to a less abrasive envierment. Brad

SirRoxalot
freely admits to licking rocks

Member since October 2003
Posts: 790

Pre-grit rough tumble ¿ Mar 1, 2008 17:09:43 GMT -5

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Post by SirRoxalot on Mar 1, 2008 17:09:43 GMT -5

I did a tumbling demo and ran a tumbler full of feldspar dry all day. The edges were a bit rounded. I suspect it would be useless for anything tough and hard like quartz. Grit is cheap, but there's some possibility there for soft stuff.

SirRoxalot

johnjsgems
gets rocks for Christmas

Member since August 2007
Posts: 6,959

Pre-grit rough tumble ¿ Mar 3, 2008 0:04:38 GMT -5

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Post by johnjsgems on Mar 3, 2008 0:04:38 GMT -5

Captbob, you are right that grit is completely not needed. Rivers and oceans do it all the time. Start a load now and e-mail me in a thousand years and let me know how it works for you. Silicon Carbide is harder than the more commonly tumbled rocks so it will speed up the process.

John at JS Gems

www.jsgemslapidary.com

captbob no longer being taken for granite St. Pete FL Member since December 2007 Posts: 8,186	Pre-grit rough tumble ¿ Mar 3, 2008 0:09:40 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by captbob on Mar 3, 2008 0:09:40 GMT -5 < calculating electric bill > I was just askin'
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geogoddess spending too much on rocks Member since December 2007 Posts: 287	Pre-grit rough tumble ¿ Mar 3, 2008 1:30:57 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by geogoddess on Mar 3, 2008 1:30:57 GMT -5 I think the situation that Cutter mention is the best, if you wanna "pre-tumble" using river sand or something. Particularly if your not in any rush.

cutter
starting to spend too much on rocks

Member since February 2008
Posts: 129

Pre-grit rough tumble ¿ Mar 4, 2008 8:43:43 GMT -5

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Post by cutter on Mar 4, 2008 8:43:43 GMT -5

After having just cleaned up broken glass, I wondered if one could use broken tempered glass as a XXX course grit. Tempered glass breaks into very uniformed pea size bits and is the same hardness as Quartz. I am sure it isn't friendly on barrels. There would no problem getting tons of the stuff for free from any glass shop.

captbob
no longer being taken for granite

St. Pete FL

Member since December 2007
Posts: 8,186

Pre-grit rough tumble ¿ Mar 4, 2008 9:03:42 GMT -5

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Post by captbob on Mar 4, 2008 9:03:42 GMT -5

Hey Cutter, I've read here that this safety glass can be used much as you would use a ceramic media, as a filler and to help move the grit around. Seems like a good, inexpensive idea and I doubt it could be any worse for the tumbler than sharp edges of hammer busted rocks.

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