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Started by Thy Will Be Done, April 14, 2023, 11:49:02 AM
Quote from: 3D Anvil on April 14, 2023, 05:59:37 PMHere's an interesting quote from a company that sells both diamond and CBN grinding wheels:"Diamond is composed of pure carbon and is produced under high heat and pressure. When Diamond is used to grind hardened steel it causes a chemical reaction and essentially begins to form graphite and lose its strength.So what makes CBN better for working with hardened steels? CBN is not composed of carbon atoms, instead it is formed with boron and nitride under pressure and heat. Grinding hardened steels produces high temperatures, CBN has a great thermal conductivity, keeping it cool under extreme heat."But ... my impression is that this applies only, or mostly, to high-speed, high-temperature grinding. I don't know if it has any impact on a Tormek, with its low rpms and low temperatures.
Quote from: Ken S on April 15, 2023, 05:59:27 AMThe quote is confusing and does not apply to the Tormek. For an accurate picture, watch this video:https://youtu.be/38c95D6z5D8Håkan Persson, superabrasives expert and Tormek CEO, gives a very balanced comparison between diamonds and CBN. If you watch the CBN vendors' youtubes, you will find that they use high speed dry grinders. (They recommend half speed "low speed" grinders for beginners, but use the high speed grinders in their own work. CBN is the logical choice for higher speed dry grinding.)This does not apply to low speed wet grinding. I suspect whoever posted the quote does not understand Tormek sharpening.Ken
Quote from: Thy Will Be Done on April 15, 2023, 02:17:23 PMSo it's interesting to note that he claims here the reason for diamond being chosen was that it's harder than CBN. Vadim says the reason he used CBN was because it is more impact resistant. That is an interesting property to go off of because as far as I can tell there is little impact to the abrasive as much as just slow wear (which would lend itself to hardness being the most important factor to longevity).
QuoteIn air, CBN forms a stable layer of boron oxide that prevents further oxidation up to 1300°C. However, this layer dissolves in water, so CBN wears more rapidly when water-based fluids are used than with neat oil fluids.
Quote from: Ken S on May 28, 2023, 05:45:29 PMTormek mentions that their ACC solution can be used with their standard grinding wheels. I think we must overlook arguments pertaining to high speed grinding.I also have faith that Tormek, with Håkan's lifetime of super abrasive expertise, had good reason to choose diamond wheels. Tormek could have chosen either.I am convinced that this not an either/or issue. Diamond wheels are obviously not a good candidate or higher speed dry grinders with the BGM-100. Or, for any wheel coarser than 360 grit. I have 80 and 180 grit CBN wheels. That does not prevent me from using 360/600/1200 grit diamond wheels. There is no need for all the wheels to match. Agree that either will work. Ken
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