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Post by Hard Rock Cafe on Nov 28, 2009 10:29:43 GMT -5
I'm new to cabbing and I'm struggling with little flat spots (that look like little facets) and a polish that isn't as high as it should be.
Here are my steps: 1. 80 grit SiC hard wheel; grind and shape 2. 220 grit SiC hard wheel; fine grind 3. 220 grit SiC belt on an expando drum; sanding 4. 400 grit SiC belt on an expando drum; sanding 5. 600 grit SiC belt on an expando drum; sanding 6. worn out 600 grit SiC belt on an expando drum; pre-polish 7. cerium oxide (pink) on rubber-backed damp leather buff disc
I keep the stone moving in arcs, but obviously there is something wrong with my technique.
Using very light pressure (to the point where the stone is just skimming the surface) on the 600 belts seems to help, but it doesn't eliminate the flats. Maybe I should try more pressure?
I run all the wheels at the same speed. Maybe I should use a faster speed for sanding?
I'm polishing agate, so I should get a high shine, but all I get is a dull one. I've used this same polish in tumbler with good results. I've tried more water on the buff, but all I get is smeared polish on the stone until the leather starts to dry. Maybe I should polish at a higher speed?
Thanks in advance! Chuck
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highplainsdrifter
fully equipped rock polisher
Member since December 2008
Posts: 1,266
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Post by highplainsdrifter on Nov 28, 2009 10:38:03 GMT -5
The flat spots are generated during grinding/doming. You can reduce them by doing more feathering. Use an up and down sweeping motion from the edge of the bezel to top of the dome. Taller domes will help also. Any remaining flat spots need to be removed at the first sanding step, else they will remain until the end. Spend more time sanding on the 220 belt and keep drying the cab and inspecting until the flats are removed. Don't move on until you get them all out. I use moderate pressure during sanding. Dan
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Post by Hard Rock Cafe on Nov 28, 2009 11:27:24 GMT -5
Thank you Dan! That's helpful advice from one of the masters of the craft. I thought I was causing the problem at later stages, but it's right at the beginning.
They're hard to see when the stone is dry, but they really show up in polishing. I guess I'll have to get out the magnifiers.
Chuck
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adrian65
Cave Dweller
Arch to golden memories and to great friends.
Member since February 2007
Posts: 10,777
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Post by adrian65 on Nov 28, 2009 12:17:20 GMT -5
I agree, looking at the steps you're doing I think the flat spots are done in the 2nd step, so you should pay more attention to the steps 3 and 4 (expando 200 and 400).
Adrian
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Post by Hard Rock Cafe on Nov 28, 2009 17:02:33 GMT -5
Thanks Adrian!
How about the polish? It seems like I should still get a good shine, even if the surface isn't even...
Unless you're saying that the flat spots and also indicate scratches...
Chuck
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Mudshark
fully equipped rock polisher
Diplomacy is the art of saying 'Nice doggie' until you can find a rock. Will Rogers
Member since December 2008
Posts: 1,083
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Post by Mudshark on Nov 28, 2009 17:13:36 GMT -5
I'm just a beginner at cabbing but I got rid of the flat spots by drying the cab and using a magnifier after each of the two grinding wheels.I was also using cerium at first but I get a better shine with Tin oxide.
Mike
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Post by bobby1 on Nov 28, 2009 18:18:42 GMT -5
I always use well worn belts for my 400 and 600 sanding. I also push rather firmly into the belts for these steps. If your belts are new and stiff they will actually sand flat spots onto the cab. I rather vigorously jam a scrap rock into the belt for a few minutes to break it in and make it softer brfore using it. Bob
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NDK
Cave Dweller
Member since January 2009
Posts: 9,440
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Post by NDK on Nov 28, 2009 21:17:15 GMT -5
I've found sometimes I really need to lean on the cab when polishing. Maybe I'm being too forceful, but it works. I'm guessing the heat generated helps out a little. Be careful not to get them too hot though, they could fracture. All I've used for polish for my cabs is a leather pad on a plastic disc with no backing (the one shown in my low-buck flat lap thread), and for polish I use "polish" from my local hobby store purchased for tumbling. I honestly have no clue what it is, but it's a white powder.
Hang in there Chuck, you'll get it yet!
Nate
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Post by Hard Rock Cafe on Nov 29, 2009 10:02:44 GMT -5
Thanks Mike, Bob, and Nate!
Yes, these are new belts, so I'll try breaking them in a little.
I do put enough pressure on the stone for it to get hot when polishing. I've also tried tin oxide, but the results are the same. My polish head is domed, which helps when doing concave surfaces.
I'll try all of your suggestions and let you know my progress.
Chuck
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Post by Bejewelme on Nov 30, 2009 11:41:30 GMT -5
Chuck: You know how I struggle, you must use magnification and you must dry the stones, if you have a dop pot or something lay it on there inbetween to dry out and then look at it, if you get the flats out early each step is so much easier. Also take a marker and mark the flat, then you can see that you are grinding on the right spot of the cab, it is easy to think you are grinding where you want and then you are a little off, that has helped me get nicer domes. Keep at it, cabbing is hard!!! Amber Cant wait to see the end result!!!
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