11-07-2018, 12:25 PM
Sounds pretty comprehensive Mark. We think that we'll go lower in order to compliment your tests. We'll buy some 200° Tempilaq (or whatever brand Mcmaster Carr sells) and see if we can find the lower limit. Perhaps half the test area thinned and half straight.
Applying different approaches to the same problem is often a good way to answer questions. We'll perform the experiments, collect the data, and let folks apply it as they wish. Quite frankly, we may be reinventing the wheel here in consideration of the results provided by the two studies we provided a couple of pages ago in this thread. One study considered the range of material removal from 6 - 20 microns and the other 0 - 40 microns and the grinding temperatures attained thereof. One would like to think that the researchers were studying material removal amounts that were germane to common industry practice. If we could decide approximately how much material is removed in a single light pass on the Kally then our answers may be already before us. Is it reasonable to think that only a very few microns of material might be removed by an attentive knife sharpener using a belt grinder? Here's are excerpts from a very perfunctory search of the internet;
SOURCE https://en.wikipedia.org/wiki/Grinding_(...e_cutting)
"Grinding practice is a large and diverse area of manufacturing and toolmaking. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is "regular" machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft’s diameter by half a thousandth of an inch or 12.7 μm."
"Surface grinding uses a rotating abrasive wheel to remove material, creating a flat surface. The tolerances that are normally achieved with grinding are ±2×10−4 inches (5.1 μm) for grinding a flat material and ±3×10−4 inches (7.6 μm) for a parallel surface.[1]"
"Tolerances for cylindrical grinding are held within ±0.0005 inches (13 μm) for diameter and ±0.0001 inches (2.5 μm) for roundness. Precision work can reach tolerances as high as ±0.00005 inches (1.3 μm) for diameter and ±0.00001 inches (0.25 μm) for roundness. Surface finishes can range from 2 microinches (51 nm) to 125 microinches (3.2 μm), with typical finishes ranging from 8 to 32 microinches (0.20 to 0.81 μm)."
It is worth noting that the article distinguishes between grinding and surface finishing. Polishing would seem to be yet still even further down the metal removal scale. We found one reference to polishing that described it as metal removal at the "molecular level". Additionally, grind depth seems to be primarily controlled not by the machines ability to index accurately very minute distances (as in milling operations) but rather by rotational or linear speed of the abrasive, material feed rate and by applied grinding force. These same factors seem to be the ones discussed at length by skilled belt sharpeners ad nauseum.
Assuming the accuracy of the article, then yes, metal removal depths of only a few microns are not only feasible but typical during machine grinding operations. The question then seems to be "are we humans, in a hand-held manner, capable of limiting the depth of our grinding passes to sub 10 micron levels?" If we are trying to create an edge apex of sub-micron width, 10 microns does seem a-plenty. If we are able, then our overheating fears might seem completely unfounded. If not, and for those interested in sharpening a knife inside a few minutes, perhaps we should consider investing in automated grinding/knife sharpening machines.
In the meantime, we'll get our 200° Tempilaq on order.
Applying different approaches to the same problem is often a good way to answer questions. We'll perform the experiments, collect the data, and let folks apply it as they wish. Quite frankly, we may be reinventing the wheel here in consideration of the results provided by the two studies we provided a couple of pages ago in this thread. One study considered the range of material removal from 6 - 20 microns and the other 0 - 40 microns and the grinding temperatures attained thereof. One would like to think that the researchers were studying material removal amounts that were germane to common industry practice. If we could decide approximately how much material is removed in a single light pass on the Kally then our answers may be already before us. Is it reasonable to think that only a very few microns of material might be removed by an attentive knife sharpener using a belt grinder? Here's are excerpts from a very perfunctory search of the internet;
SOURCE https://en.wikipedia.org/wiki/Grinding_(...e_cutting)
"Grinding practice is a large and diverse area of manufacturing and toolmaking. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is "regular" machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft’s diameter by half a thousandth of an inch or 12.7 μm."
"Surface grinding uses a rotating abrasive wheel to remove material, creating a flat surface. The tolerances that are normally achieved with grinding are ±2×10−4 inches (5.1 μm) for grinding a flat material and ±3×10−4 inches (7.6 μm) for a parallel surface.[1]"
"Tolerances for cylindrical grinding are held within ±0.0005 inches (13 μm) for diameter and ±0.0001 inches (2.5 μm) for roundness. Precision work can reach tolerances as high as ±0.00005 inches (1.3 μm) for diameter and ±0.00001 inches (0.25 μm) for roundness. Surface finishes can range from 2 microinches (51 nm) to 125 microinches (3.2 μm), with typical finishes ranging from 8 to 32 microinches (0.20 to 0.81 μm)."
It is worth noting that the article distinguishes between grinding and surface finishing. Polishing would seem to be yet still even further down the metal removal scale. We found one reference to polishing that described it as metal removal at the "molecular level". Additionally, grind depth seems to be primarily controlled not by the machines ability to index accurately very minute distances (as in milling operations) but rather by rotational or linear speed of the abrasive, material feed rate and by applied grinding force. These same factors seem to be the ones discussed at length by skilled belt sharpeners ad nauseum.
Assuming the accuracy of the article, then yes, metal removal depths of only a few microns are not only feasible but typical during machine grinding operations. The question then seems to be "are we humans, in a hand-held manner, capable of limiting the depth of our grinding passes to sub 10 micron levels?" If we are trying to create an edge apex of sub-micron width, 10 microns does seem a-plenty. If we are able, then our overheating fears might seem completely unfounded. If not, and for those interested in sharpening a knife inside a few minutes, perhaps we should consider investing in automated grinding/knife sharpening machines.
In the meantime, we'll get our 200° Tempilaq on order.