Flattened natural quartz slab for microbeveling
Posted by alkali
|
Flattened natural quartz slab for microbeveling October 05, 2023 07:50AM |
Registered: 2 years ago Posts: 64 |
While wandering around in the middle of nowhere I found an interesting rock. Later I ground a flat face on it with loose silicon carbide (SiC) grit and a lot of effort. It has turned out to be a usable sharpening surface.
Properties of the rock:
- Roughly 120mm by 90mm by 25mm. Slablike.
- Very hard.
- Waxy luster. The more rounded and worn parts of the surface look a bit like cold animal fat.
- Devoid of visible porosity/voids.
- Streaky and slightly translucent.
- Microcrystalline/cryptocrystalline (individual crystals are too small to be seen by eye).
- Based on observations above, principal mineral appears to be quartz. (See [www.quartzpage.de] to dive into a rabbit hole about quartz and its behavior.)
- Rock is presumably some kind of quartzite, though I am not certain.
Grinding:
- Done by hand.
- The substrate for grinding was a roughly 12 by 12 by 1.5 inch concrete paver tile (this cost about US$2 at a hardware store) resting on rubber coasters in a steel kitchen sink.
- The abrasive used was 80 grit loose SiC because it was what I had around. This breaks down into bluish toothpaste-like slurry very quickly, and cutting presumably slows down as it does so. I used a small spoonful at a time, rinsing the plate each time before replacing the grit. (This was based on speculation that mixing fresh grit with broken-down grit might cause the fresh grit to break down even faster, but it was only speculation. I don't know if rinsing made a difference.)
- Only one face was ground. The other face was left as found, smooth and flattish but uneven. Side surfaces were ground in places, and not in others, to clean the rock up a bit. Sharp edges of the ground face were chamfered.
- After grinding the rock is about 23mm thick. The usable sharpening area is about 80mm by 85mm.
- Weight of rock before grinding was 596g.
- Weight of rock after grinding is 580g.
- 16g of rock was ground away, consuming 62g of SiC abrasive grit.
(Note: I also used a SiC scythe stone to lightly chamfer the edges of the rock. The small amount of abrasive lost from the scythe stone is not included here, though any rock removed is included.)
(See Stamp's mention of "G ratio" here: [oldforum.beyondt01micron.com] . )
The ground face looks a lot like the rock in this image:
[en.wikipedia.org]
(Neither the image linked above nor the rock in the image are mine.)
Thoughts after the grinding process:
- This was even more work than it looked like ahead of time.
- Coarser grit would have been helpful.
- Less brittle grit would have been helpful. SiC grit breaks down very quickly.
(This has been noted by others.
Stefan Wolf mentions Soft Arkansas crushing SiC grit quickly here: [oldforum.beyondt01micron.com] .
Cliff Stamp mentions SiC grit being crushed quickly here: [oldforum.beyondt01micron.com] . )
- Rough-cutting the rock with a tile saw / rock saw ahead of time would have saved a great deal of grinding time and effort.
- An enterprising person could have salvaged the broken-down grit and saved it for other work. I did not.
- The concrete tile is slightly concave now. In the center, aggregate pieces are visible in cross-section. The aggregate pieces are very slightly proud of the surrounding cement surface, presumably due to their greater abrasion resistance.
The rock after grinding:
- The bottom (unground) surface is uneven, but is flat enough that if the rock is placed on a dishrag it is stable enough to be used as a small benchstone. I prefer to use it handheld.
- The surface texture is whatever was there at the end of the last round of grinding. I have not gone out of my way to condition it in any particular way. If my assumptions about the material (that it is low porosity cryptocrystalline quartz) are correct, then it should be possible to apply a variety of different finishes to the surface.
To the touch, the surface texture seems:
- much smoother than that of a piece of large-pored novaculite (sold as "soft" Arkansas) I have
- smoother than that of my Norton fine India (both the used side and the side I leave unused as a reference)
- just barely smoother than that of a piece of small-pored novaculite (also sold as "soft" Arkansas) I have
- similar to, or just barely coarser than, that of my DMT XF plate
But of course the superficial surface texture of a sharpening surface and the scratch pattern it produces on a given material are two different things.
At some point I should see what the scratch pattern created by this surface really is:
- Mirror polish a test blade edge bevel.
- Grind the edge bevel with the surface in question.
- Have a look at the scratch pattern under magnification.
- Repeat the process using other abrasive surfaces I have here.
I haven't done this, so I can't say much yet about the scratch pattern this rock produces.
Sharpening:
In both cases below, mineral oil was used as a lubricant.
Using this rock as a microbeveling surface, and after some screwing around, I was able to push-cut U-line catalog paper, which I had not been able to do before. So far so good.
- The knife was a Dexter Russell 5"x1" rectangular shop knife that I use for practice and experiments. Model X5X1S, SKU 60090, full-height flat grind, unknown steel.
- I do not remember the cutting direction or the distance from holding point.
- If having surfaces finer than Norton fine India around is going to make sharpening for push-cutting easier, I should probably obtain some commercial examples. (My DMT XF plate doesn't count, as there is just enough grit contamination that I avoid using it.)
- Yet I know that I should be able to use my usual microbeveling surface, a Norton fine India, to create push-cutting edges. I simply haven't yet. I should show some discipline and make it work.
I used this rock to apply a microbevel to a Benchmade Mini Griptilian (154CM).
- The edge bevel was prepared beforehand with a King 1000 (muddy waterstone). I forget what I used before that (for shaping), if anything.
- For utility purposes (mostly angled push-cutting of packaging) the resulting edge is at least as functional as the Norton fine India edge I have used in the past, and maybe better.
- How much of this is the rock and how much of this is simply me getting better at what I am doing is not clear. I suspect it is mostly the latter. I hope it is the latter.
- This rock will microbevel 154CM without any problem. Good to know.
Conclusions:
- It is possible to turn a rock found on the ground, if it is the right rock, into a usable sharpening surface using a minimal skillset and cheap equipment.
- It is possible for a person with moderate sharpening skill to use the above surface productively.
- This can be worthwhile for education and entertainment (and satisfaction). It is unlikely to save anyone money or time over a commercial product unless they happen to already have a suitable rock, a rock saw, and lapping materials on hand.
Edited 1 time(s). Last edit at 10/05/2023 09:30PM by alkali.
Properties of the rock:
- Roughly 120mm by 90mm by 25mm. Slablike.
- Very hard.
- Waxy luster. The more rounded and worn parts of the surface look a bit like cold animal fat.
- Devoid of visible porosity/voids.
- Streaky and slightly translucent.
- Microcrystalline/cryptocrystalline (individual crystals are too small to be seen by eye).
- Based on observations above, principal mineral appears to be quartz. (See [www.quartzpage.de] to dive into a rabbit hole about quartz and its behavior.)
- Rock is presumably some kind of quartzite, though I am not certain.
Grinding:
- Done by hand.
- The substrate for grinding was a roughly 12 by 12 by 1.5 inch concrete paver tile (this cost about US$2 at a hardware store) resting on rubber coasters in a steel kitchen sink.
- The abrasive used was 80 grit loose SiC because it was what I had around. This breaks down into bluish toothpaste-like slurry very quickly, and cutting presumably slows down as it does so. I used a small spoonful at a time, rinsing the plate each time before replacing the grit. (This was based on speculation that mixing fresh grit with broken-down grit might cause the fresh grit to break down even faster, but it was only speculation. I don't know if rinsing made a difference.)
- Only one face was ground. The other face was left as found, smooth and flattish but uneven. Side surfaces were ground in places, and not in others, to clean the rock up a bit. Sharp edges of the ground face were chamfered.
- After grinding the rock is about 23mm thick. The usable sharpening area is about 80mm by 85mm.
- Weight of rock before grinding was 596g.
- Weight of rock after grinding is 580g.
- 16g of rock was ground away, consuming 62g of SiC abrasive grit.
(Note: I also used a SiC scythe stone to lightly chamfer the edges of the rock. The small amount of abrasive lost from the scythe stone is not included here, though any rock removed is included.)
(See Stamp's mention of "G ratio" here: [oldforum.beyondt01micron.com] . )
The ground face looks a lot like the rock in this image:
[en.wikipedia.org]
(Neither the image linked above nor the rock in the image are mine.)
Thoughts after the grinding process:
- This was even more work than it looked like ahead of time.
- Coarser grit would have been helpful.
- Less brittle grit would have been helpful. SiC grit breaks down very quickly.
(This has been noted by others.
Stefan Wolf mentions Soft Arkansas crushing SiC grit quickly here: [oldforum.beyondt01micron.com] .
Cliff Stamp mentions SiC grit being crushed quickly here: [oldforum.beyondt01micron.com] . )
- Rough-cutting the rock with a tile saw / rock saw ahead of time would have saved a great deal of grinding time and effort.
- An enterprising person could have salvaged the broken-down grit and saved it for other work. I did not.
- The concrete tile is slightly concave now. In the center, aggregate pieces are visible in cross-section. The aggregate pieces are very slightly proud of the surrounding cement surface, presumably due to their greater abrasion resistance.
The rock after grinding:
- The bottom (unground) surface is uneven, but is flat enough that if the rock is placed on a dishrag it is stable enough to be used as a small benchstone. I prefer to use it handheld.
- The surface texture is whatever was there at the end of the last round of grinding. I have not gone out of my way to condition it in any particular way. If my assumptions about the material (that it is low porosity cryptocrystalline quartz) are correct, then it should be possible to apply a variety of different finishes to the surface.
To the touch, the surface texture seems:
- much smoother than that of a piece of large-pored novaculite (sold as "soft" Arkansas) I have
- smoother than that of my Norton fine India (both the used side and the side I leave unused as a reference)
- just barely smoother than that of a piece of small-pored novaculite (also sold as "soft" Arkansas) I have
- similar to, or just barely coarser than, that of my DMT XF plate
But of course the superficial surface texture of a sharpening surface and the scratch pattern it produces on a given material are two different things.
At some point I should see what the scratch pattern created by this surface really is:
- Mirror polish a test blade edge bevel.
- Grind the edge bevel with the surface in question.
- Have a look at the scratch pattern under magnification.
- Repeat the process using other abrasive surfaces I have here.
I haven't done this, so I can't say much yet about the scratch pattern this rock produces.
Sharpening:
In both cases below, mineral oil was used as a lubricant.
Using this rock as a microbeveling surface, and after some screwing around, I was able to push-cut U-line catalog paper, which I had not been able to do before. So far so good.
- The knife was a Dexter Russell 5"x1" rectangular shop knife that I use for practice and experiments. Model X5X1S, SKU 60090, full-height flat grind, unknown steel.
- I do not remember the cutting direction or the distance from holding point.
- If having surfaces finer than Norton fine India around is going to make sharpening for push-cutting easier, I should probably obtain some commercial examples. (My DMT XF plate doesn't count, as there is just enough grit contamination that I avoid using it.)
- Yet I know that I should be able to use my usual microbeveling surface, a Norton fine India, to create push-cutting edges. I simply haven't yet. I should show some discipline and make it work.
I used this rock to apply a microbevel to a Benchmade Mini Griptilian (154CM).
- The edge bevel was prepared beforehand with a King 1000 (muddy waterstone). I forget what I used before that (for shaping), if anything.
- For utility purposes (mostly angled push-cutting of packaging) the resulting edge is at least as functional as the Norton fine India edge I have used in the past, and maybe better.
- How much of this is the rock and how much of this is simply me getting better at what I am doing is not clear. I suspect it is mostly the latter. I hope it is the latter.
- This rock will microbevel 154CM without any problem. Good to know.
Conclusions:
- It is possible to turn a rock found on the ground, if it is the right rock, into a usable sharpening surface using a minimal skillset and cheap equipment.
- It is possible for a person with moderate sharpening skill to use the above surface productively.
- This can be worthwhile for education and entertainment (and satisfaction). It is unlikely to save anyone money or time over a commercial product unless they happen to already have a suitable rock, a rock saw, and lapping materials on hand.
Edited 1 time(s). Last edit at 10/05/2023 09:30PM by alkali.
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