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- Jun 7, 2002
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This question is open not just to knife makers, polishers and sharpeners. Gemologists, craftsmen, and other industrial workers are welcome to add. Perhaps describing your work would be beneficial for these fora.
Mine is 30 microns (0.03 mm) most rocks and minerals are actually translucent and a very thin section can be analyzed in a polarizing microscope. Preparing mineral samples for microscopy is what i did for a short time with our geologic survey:
1. Cut a slab of that rock/mineral your want to examine using a tungsten saw. Make sure one side is less than 1 inch wide and 2 inches long.
2. Polish the above-mentioned side of the slab on a lapidary (horizontal steel wheel.) First put a small mound of medium-grit (~.5mm-.2mm) carbonrundum powder in the middle and wet with water. Turn on the wheel and polish your work to remove the saw marks and rough features. Move the work side-to-side in a radial direction in relation to the wheel. This will prevent the steel wheel from concaving (and your work from convexing.) It has to be perfectly flat.
3. Shift to fine (< 0.1 mm) carborundum to (visibly) smoothen the work.
4. Final polish of the work is done manually on a glass plate using aluminum oxide power (micron-size).
5. Glue that polished side of your work on a glass slide using melted canada balsam. Care should be taken to prevent bubbles of air in the balsam between the glass and the mineral surface.
6. Back to the tungsten saw. Slice off the main portion of the mineral slab, leaving only a chip glued to the glass slize (less than 3mm thickness.)
7. Back to the lapidary. Stick a small suction cup on the opposite side of the glass slide to use as a handle. Use medium grit to reduce the chip sample to less than 1 mm thickness (careful this time.) Use the fine to reduce below 0.1 mm (100 microns.)
8. Below 100 microns, you stand to work anywhere between 2 hours and 2 days on the lapidary and glass plate, depending on the mineral hardness. In the case of massive quartz, I spent 3 days on my first time. Experienced polishers can actually "see" 0.03mm or 30 microns. I couldn't. For quartz, you determine correct thickness by going to the polarizing microscope and viewing your work. Under crossed polars, 0.03mm of quartz should appear pale yellow whereas mine looked dark violet (> 60 microns!)
9. So back to the glass plate. One polisher already helped me out by clipping the slide down and grinding it to 50 microns using a diamond wheel. anything smaller than 50, the wheel can't help me. so back to the glass and hand-grind using corundum powder. finally, the foreman looked at my sample and said "it think you've finally done it." i went back to the microscpe and sure enough, it was pale yellow. one of my best experiences as a young geologist.
***
Mine is 30 microns (0.03 mm) most rocks and minerals are actually translucent and a very thin section can be analyzed in a polarizing microscope. Preparing mineral samples for microscopy is what i did for a short time with our geologic survey:
1. Cut a slab of that rock/mineral your want to examine using a tungsten saw. Make sure one side is less than 1 inch wide and 2 inches long.
2. Polish the above-mentioned side of the slab on a lapidary (horizontal steel wheel.) First put a small mound of medium-grit (~.5mm-.2mm) carbonrundum powder in the middle and wet with water. Turn on the wheel and polish your work to remove the saw marks and rough features. Move the work side-to-side in a radial direction in relation to the wheel. This will prevent the steel wheel from concaving (and your work from convexing.) It has to be perfectly flat.
3. Shift to fine (< 0.1 mm) carborundum to (visibly) smoothen the work.
4. Final polish of the work is done manually on a glass plate using aluminum oxide power (micron-size).
5. Glue that polished side of your work on a glass slide using melted canada balsam. Care should be taken to prevent bubbles of air in the balsam between the glass and the mineral surface.
6. Back to the tungsten saw. Slice off the main portion of the mineral slab, leaving only a chip glued to the glass slize (less than 3mm thickness.)
7. Back to the lapidary. Stick a small suction cup on the opposite side of the glass slide to use as a handle. Use medium grit to reduce the chip sample to less than 1 mm thickness (careful this time.) Use the fine to reduce below 0.1 mm (100 microns.)
8. Below 100 microns, you stand to work anywhere between 2 hours and 2 days on the lapidary and glass plate, depending on the mineral hardness. In the case of massive quartz, I spent 3 days on my first time. Experienced polishers can actually "see" 0.03mm or 30 microns. I couldn't. For quartz, you determine correct thickness by going to the polarizing microscope and viewing your work. Under crossed polars, 0.03mm of quartz should appear pale yellow whereas mine looked dark violet (> 60 microns!)
9. So back to the glass plate. One polisher already helped me out by clipping the slide down and grinding it to 50 microns using a diamond wheel. anything smaller than 50, the wheel can't help me. so back to the glass and hand-grind using corundum powder. finally, the foreman looked at my sample and said "it think you've finally done it." i went back to the microscpe and sure enough, it was pale yellow. one of my best experiences as a young geologist.
***
. Today I lathed 2 pieces of nylon at 12. 03 to 12.05 mm for a 12.00 tube
I finished on 1.0 micron diamonds which is not all that fine (I used to go down to 0.25) but I have found that there are many limits that exist in materials and methods...and these recent results demonstrate to me that I was previously wasting time with grits smaller than 1.0 microns as evidenced by the superior results I recently achieved. 
