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Post by Jugglerguy on Mar 28, 2014 14:52:32 GMT -5
I just attempted my first Petoskey stone shaped like the state of Michigan. It's not perfect, but I'm really happy with the way it turned out. I haven't figured out how to polish the sides yet. I could probably do something with my Dremel, but the bays are going to be difficult. The whole state shape thing would have been easier if I lived in Ohio or Wyoming. Next time, I might include the U.P.  |
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panamark
fully equipped rock polisher
Member since September 2012
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Post by panamark on Mar 28, 2014 15:56:30 GMT -5
That is a fabulous "mitten" Rob! How did you cut it and get it so perfect? (Maybe a bit of a bump easterly-wide around Port Huron and for some reason Alpena seems exaggerated, ha but still, you could navigate off that thing!)
What a GREAT job!
BTW: my wife (from away) still shakes her head whenever I hold up my hand and point to a spot to show people where I was born :-)
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Post by Jugglerguy on Mar 28, 2014 22:27:33 GMT -5
Does your wife have a better way of showing where you're from? I think she's just jealous that her state isn't the shape of a hand.
I cut the rock on my 10 inch saw. It was pretty easy. The hardest part was cutting the map out of paper and tracing it on the stone. After that was done, I just used the side of my blade to shape everything.
Does anyone have any ideas for how to polish the edges? It seems like there should be something that I could put in my Dremel or my drill press to do the job, but I'd need different grits. The real problem is getting in the bays, so it would have to be something pretty small.
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jamesp
Cave Dweller 
Member since October 2012
Posts: 36,603
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Post by jamesp on Mar 29, 2014 5:55:03 GMT -5
Well done Rob. Dremel diamond bit with sharp point should get details. Like a dentist shape bit. Can petosky be tumbled in 500 to do some final smoothing?
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Post by Jugglerguy on Mar 29, 2014 8:30:56 GMT -5
It might make it through 500, but Petoskeys don't tumble well and can't be polished in a tumbler. I'd also like to keep the shape nicely defined, with sharp edges.
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panamark
fully equipped rock polisher
Member since September 2012
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Post by panamark on Mar 29, 2014 9:40:14 GMT -5
Rob,
Amazing you could do that detail with the trim saw.
you may be able to get some sandpaper tape stuff, do they call it plumber's something? Tear it into a narrow enough strip to fit in the bays and with the rock in a padded vice, just saw the paper back and forth to smooth the bays. Or even some good cloth or strip of leather dipped in a paste of grit might work. A dremel would work but you would have to be real careful it doesn't chatter and skip onto the rock face.
ps: Go BLUE! Close one last night!
pps: my wife is from a misshapen state where they just have to get out a paper map to show. She IS jealous!
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Post by Jugglerguy on Mar 29, 2014 9:45:05 GMT -5
Hey Mark, I thought about just getting some cloth wet/dry sandpaper and doing the edges by hand. Since Petoskey is so soft and the edges are pretty thin, I could probably do it fairly quickly. The leather strip is an interesting idea too, I'll try that if the sandpaper doesn't work.
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ojhoff
starting to shine!
Member since September 2012
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Post by ojhoff on Mar 29, 2014 11:34:38 GMT -5
That's different! Now do one of the U.P.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,603
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Post by jamesp on Mar 29, 2014 12:16:15 GMT -5
A lard coated cotton shoe string dipped in SiC can do well. the grit salesman says lard holds SiC just right for lappers. Does not sling off up to pretty high speeds.
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Post by Jugglerguy on Mar 29, 2014 12:54:43 GMT -5
Lard is something that I would never have thought of for lapidary uses. That will be a last resort though.
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Post by Jugglerguy on Mar 29, 2014 13:19:14 GMT -5
I just tried out some 3M automotive wet/dry sandpaper. I cut a thin strip and wrapped it around a dowel. I started with 320 and ended with 800 (I think it was 400 and 600 in between), then Zam. I won't be able to use my Dremel to apply Zam in the bays, so I might have to skip them. Can you tell which side I finished?  |
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panamark
fully equipped rock polisher
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Post by panamark on Mar 29, 2014 14:29:21 GMT -5
looks great!!
Ha, I was just thinking you are doing to miniature MI shoreline what the ice is gonna do for real during breakup. In fact you may have to cut some new bays before summer comes ;-)
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Post by Jugglerguy on Mar 29, 2014 14:41:50 GMT -5
We drove up to Marquette earlier this week to see my mom and sister. I was surprised that there was a lot of open water on Lake Huron between here and the bridge. It was completely frozen over at the bridge though. We could see where the ice breakers had made a path through the straits.
I can't wait to get out and do some rock huntin'. I have trips planned for both Lake Michigan and Lake Superior.
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Post by Drummond Island Rocks on Mar 29, 2014 18:32:59 GMT -5
very cool Rob. I was just looking at our club the other day and they sell Petoskey kits for kids ($2.00) that have a small natural stone, 600 wet sand paper, a piece of cloth and a small amount of cerium oxide. That really all that's really all that's needed so you I imagine the 600 paper you used followed but a cloth with polish will work just fine. I do think the sides are nearly as important as the face for these anyway.
Chuck
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Post by Jugglerguy on Mar 29, 2014 18:46:20 GMT -5
I wonder why they include cerium oxide instead of aluminum oxide? I did pretty well with 800 grit sand paper and Zam, but I couldn't get the Zam into the bays. I might have to try a lard/polish string.
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jamesp
Cave Dweller
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Post by jamesp on Mar 30, 2014 6:49:14 GMT -5
The grit salesman said that his military customer has switched from expensive diamond dust to silicon carbide since having success with lard as a grit holding mechanism.
They run lappers on precision metal parts in large quantity. It is laughed about but effective. The salesman suggested i run SiC/lard on lapping stones.
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