richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 19, 2016 8:28:31 GMT -5
I am still working on my agates in my rotary tumbler and the anticipation is driving me crazy. I have been checking them every three or four days and adding more coarse grit. It seems like after 3 days 90% of the grit has broken down to a fine powder and after 4 days there are no coarse grains left at all. I have been rinsing everything out and adding fresh coarse grit and things seem to be progressing nicely.
Before I started my agates I had been working on some gabbro and had the coarse stage (30-90 grit then 120-220 grit) complete and the rocks were looking and feeling silky smooth with no pits or cracks that I could see. Had moved to 500 grit and after three days I checked on the rocks to see how they were doing and to my disappointment I found that they were heavily pitted.
My formula was 1lb of rocks, 1lb of small ceramic media (non-abrasive), 2tbsp 500grit ALO and water up to the top of the rocks/media. I tried to be very careful not to overfill the barrel and when I rotated it in my hand it sounded like everything was moving nicely.
I then started again with the 120-220 grit and got them smooth again. This time I purchased a vibratory tumbler from Harbor Freight and placed the rocks inside in the following formula.
~1lb of gabbro ~3lb ceramic media 2 tbsp 500 grit ALO
Then I turned on the machine and added water until I could see everything was moving and coated with a thin film of ALO slurry. I let this run for 12 hours and once again I found that everything was pitted.
Any suggestions? My hope was that the vibratory tumbler would be gentler on the rocks but that doesn’t seem to be the case. Other than reduced cycle time, is there any advantage to a vibratory tumbler over a rotary tumbler? I must say that the vibratory tumbler makes a lot more noise than my little Harbor Freight rotary tumbler.
Thanks
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victor1941
fully equipped rock polisher
Member since November 2011
Posts: 1,983
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Post by victor1941 on Jul 19, 2016 21:27:21 GMT -5
If my thought is correct you are tumbling a material that has minerals of different hardness that are causing your problem. I would start with a material with equal hardness.
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Deleted
Deleted Member
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Post by Deleted on Jul 19, 2016 22:54:34 GMT -5
If my thought is correct you are tumbling a material that has minerals of different hardness that are causing your problem. I would start with a material with equal hardness. Undercutting should be worse in coarse grind, maybe? I wonder is his vibe is properly secured? Or ia it free to bounce?
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 20, 2016 10:57:16 GMT -5
Victor1941, yes as I understand it you are correct that the gabbro is composed of two materials. I am definitely limited on my knowledge of geology but I believe gabbro is usually a pyroxene that is usually pretty soft like 5 or 6 and feldspar that is hardness of around 6. It seems like there isn’t a huge difference between the base materials. However, from what I have been told gabbro refers to a pretty wide range of rocks so I don’t really know what I am dealing with. The material I am trying to tumble/polish was sold under the name “indigo gabbro” and was purchased from a seller on amazon.com.
I believe this material can be polished and I very much would like to polish mine. I appreciate that it might not be the easiest material to polish but I do have a strong desire to get the job done. I guess what I am looking for here is any tips from those experience polishing softer materials. My rocks are getting smaller and smaller as I keep trying to redo them and I hope I can get some shiny rocks before they are reduced to a pile of dust.
All: As an update, I ended up trying some jasper and agate in the Harbor Freight vibratory tumbler. It has published capacity of 5lbs. I used the following in the vib:
3lbs small ceramic media 1.5lbs of agates and jasper that had completed stage one (smooth surface with minimal cracks and chips…) 4tbsp of ALO 70 grit (black colored material purchased from Harbor Freight) ½ cup of sugar And water added (~1/3 cup) until the rocks were covered with moist grit and were rolling around in the vib at a rate that approximated what I saw in youtube videos showing how a vib tumbler should look when properly loaded.
I checked the rocks every two hours and added water to keep things running the way they seemed they should. After six hours I noticed that the nut that holds the lid on was starting to back out allowing the lid to loosen and for water/grit to start to splatter out of the tumbler. I spent some time getting everything running smoothly again and tried to get the lid on tight so it wouldn’t come open again. After one hour I noticed that the nut had worked its way loose again. Again I tried cleaning up everything and get the lid as secure as I could. The tumbler was started again and when I checked it in half an hour I checked on it and found that the lid had come completely off and slurry had sprayed all over the work area.
I am not sure what exactly went wrong. The vib tumbler was not “walking” around, it stayed exactly where I had placed it. I guessed that the loading might be too much so I took half a pound of rocks out along with half a pound of media making the total loading of the vib tumbler 3.5lbs of rocks/media. I also tried to make sure none of the rocks were particularly large. All of the rocks range from ½ to 1 inch in size.
This time I started it up and stayed with the vib tumbler keeping an eye on things. After a few minutes I saw that the nut was starting to turn again and re-tightened it. Again after a few more minutes it had worked its way loose.
At that point I decided it was time to seek help. I’m starting to think that a vibratory tumbler might be a bit too advanced for me at this time.
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Deleted
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Post by Deleted on Jul 20, 2016 15:16:29 GMT -5
Wrap a rubber band around the threaded shaft and the nut won't be able to back off. Tumbler must be solidly attached and stationary or the action will be too violent for stones. There ia a thread somewhere here on how Drummond Island Rocks did his...
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 20, 2016 16:27:28 GMT -5
I will try the rubber band and search for the thread. The machine doesn’t budge at all from where I put it and if I bolt it down I am not sure how I will be able to empty it when it completes a stage. My impression so far is that vibratory tumblers are a whole lot more work than rotary tumblers.
Thanks for the tip!
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Deleted
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Post by Deleted on Jul 20, 2016 16:38:04 GMT -5
The bowl is not removable?
Fuller is probably better than not full
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 20, 2016 16:43:32 GMT -5
There doesn't appear to be an easy way to remove the bowl, this was another thing that I found annoying about this unit. I can take it off but I can't see a way to do it easily and with a full bowl. I guess you do actually get something more when you pay more than $65.
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astrobouncer
off to a rocking start
Member since January 2016
Posts: 17
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Post by astrobouncer on Jul 20, 2016 17:05:43 GMT -5
The harbour freight unit isnt a rock tumbler, its for dry media . I had one and the metal bolt holding on the nut wore completely through in a matter of days. Better off just getting a lot o tumbler or the like. Or only use the harbour freight for dry tumbling.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 20, 2016 17:08:44 GMT -5
I am coming to that conclusion which leads me to my next question. My budget is limited and I am very interested in polishing softer stones. What would be a better vibratory tumbler that doesn't cost a fortune?
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Deleted
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Post by Deleted on Jul 20, 2016 17:30:37 GMT -5
I am coming to that conclusion which leads me to my next question. My budget is limited and I am very interested in polishing softer stones. What would be a better vibratory tumbler that doesn't cost a fortune? therockshed.com/tumbler1.htmlThe Lot-O is highly praised on this board.
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richardh
spending too much on rocks
Member since June 2016
Posts: 391
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Post by richardh on Jul 20, 2016 18:42:48 GMT -5
Thanks for the link. So it looks like I will need to invest ~$230 for the tumbler + an extra bowl. It does sound like a very nice piece of equipment but from what I have read it is pretty loud. I don't live alone and I don't know how long the family will handle the added noise. So far they have been good sports about my HF rotary tumbler. Is the bowl rubber or hard plastic? As I said before I am very interested in polishing some softer rocks and if I am going to make such a large investment (for me anyway) I want to be sure I am buying the right tool for the job.
I just got back from HF. I ended up returning the vibratory tumbler I had from them.
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Deleted
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Post by Deleted on Jul 20, 2016 19:03:07 GMT -5
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Post by Drummond Island Rocks on Jul 20, 2016 19:27:13 GMT -5
The loto just needs to be mounted to a 40 pound cement block. This can be as simple as a solid 8x16 block that is painted then the loto just uses two sided tape for mounting. I went a step further and stacked three 8x8x16 cinder blocks then a solid 4x8x16 on top. This raised my loto up to normal table height so I do not need to bend down to ground level three times every day to check and add water. Small price to pay to for ergonomics. Cinder blocks here are only about $1.50 each. Everyone seems to get caught up in this part but really it costs about $10 and takes about a half hour if that. Chuck
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