stefan
Cave Dweller
Member since January 2005
Posts: 14,095
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Post by stefan on Jul 18, 2012 10:12:06 GMT -5
ON to a more serious note! Obsidian is actually pretty easy to break up (if not dangerous). Eye protection, hand protestion and good footwear a MUST (not to mention long pants and a long sleeve shirt) A good crack hammer (mini sledge if you will- aprox 2 to 3 Lbs- Harbor Freight sells em CHEAP) and a flat blade stone chisel (I like Estwings- but you pay for them). Set up in an area that will allow you to collect the shards (a blue tarp set out on a flat area works). Study the rock and look for any natural break points (cracks, fractures, pits, etc). Place the chiel in these areas and start by tapping the chisel with the hammer (no need to wail on it at this point). A couple taps will tell you if it will break cleanly (you will hear the ringing sound of the fracture). If you hear the ring, then give it a whack (no you don't need to wind up and blast it, just give it a smack like you are driving a nail). Usually thats all that is required to split. Taking your time and working the larger material down to managable size will yeild nice results with little waste.
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m83striker
starting to shine!
Member since July 2012
Posts: 36
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Post by m83striker on Jul 23, 2012 19:22:25 GMT -5
I know that it is mostly up to the individual person and size of their tumbler, but what is a managable tumbling size piece of OB? I have a batch of mahogany OB in the tumbler for about 3 days in course grit and some pieces are already well rounded and getting smooth. Should I take these pieces out and replace them with more rough or leave them in their for the duration of the week like all the instruction I have read? I have been using a towel and regular hammer/chisel to get the fist size pieces down to smaller sizes.
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Post by tntmom on Jul 23, 2012 21:47:34 GMT -5
I know that it is mostly up to the individual person and size of their tumbler, but what is a managable tumbling size piece of OB? I have a batch of mahogany OB in the tumbler for about 3 days in course grit and some pieces are already well rounded and getting smooth. Should I take these pieces out and replace them with more rough or leave them in their for the duration of the week like all the instruction I have read? I have been using a towel and regular hammer/chisel to get the fist size pieces down to smaller sizes. If they are rounded nicely with no pits or cracks, I would take them out and replace with new rough. When I rough my ob in the rotary it usually takes 2 or 3 weeks (and sometimes more depending on the shape of the rough I started with) to get them rounded and flaw-free. If you have a really large tumbler then a few days might work. My largest rotary is 12lbs. As far as size, in my 12lb'er I use material that is as small as my fingernails up to a few large 1/3 fist size pieces. You need the various sizes to maximize the surface contact as much as possible to grind faster. Ceramic media from The RockShed or Kinglsey North works extremely well with ob and then you don't have to break up your ob into miniscule pieces that you can't use. What tumbler are you using?
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m83striker
starting to shine!
Member since July 2012
Posts: 36
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Post by m83striker on Jul 25, 2012 6:07:06 GMT -5
I am using a homemade tumbler that I have a couple pictures of on another post. Well, tomorrow will be a week in the course grit and I'll take everything out and inspect. Maybe the couple that I looked at during the middle of the cycle were just lucky ones that broke without many sharp edges and they smoothed out sooner. Another question, If some of them need another week in course do I reload them and fill the rest of the barrel with rough or wait till I have enough to make a full barrel and then run week 2 in course. Thanks for all the help.
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