Q.There are so many choices when it comes to buying diamond tools: single point tools, multi-point nibs, resettable and non-resettable diamonds, carat weight considerations, indexable tools, etc. I often wonder what tools I should be buying for my applications. Can you provide some guidance?
A.The application determines the tool type.
When dressing simple forms, nearly any tool type will suffice, though grit tools work well. Grit tools provide significantly longer tool life, which reduces dressing costs. Single point and grit tools are not typically used when dressing intricate forms, as the metal surrounding the diamond(s) tends to hit the sides of the wheel causing form error. Intricate forms require the use of “form tools” which have the diamond tip either “coned” or “chiseled”. The diamonds in these tools arelapped accurately to specific tip angles and radii. This makes “form tools” the preferred tool type when dressing forms.Remember, the more intricate the form, the more intricate the tool.
The terms resettable and non-resettable pertains to the diamond used in single point tools. Resettable tools contain higher quality diamonds, which have more than one point suitable for dressing. After initial diamond use, the tool is returned to the factory and the diamond is demounted then reset in a new shank at a fraction of the cost of a new tool.This process can repeat itself up to three times, as the higher quality stones have up to four settable points.
Resetting diamonds can yield a significant cost savings versus buying a new tool every time. Non-resettable tools are referred to as disposable. Disposable tools have only one settable point, and after a single use are discarded. They are the right choice when a low initial cost is the primary consideration, or resetting is not practical.
Regarding carat weight, the larger the wheel diameter (and width), the larger the carat weight should be. Follow your abrasive supplier’s guidelines. Using undersized diamond carat weights allow the stones to become superheated, even when grinding wet. Overheating the stones graphitizes (softens) them, which lead to increase wear, and poor wheel conditioning.
Indexable tools get their name from the practice of indexing diamonds radially in their holders. Over the years, many grinding operators have been reluctant to turn dressing tools, despite the advantage of extending tool life threefold.Turning a tool requires it to be loosened in the tool holder and in doing so, operators run the risk of misalignment after indexing. A slight misalignment (especially with CNC grinders) can create a dangerous situation as the diamond tip is not where (the CNC control thinks) it should be.
Indexable head tools are specifically designed to alleviate the misalignment problem, while indexing is fast and easy.Indexable tools feature a two-part construction with the head and shank as separate pieces. After the initial installation,operators simply turn the indexable head portion of the tool with a wrench, while the tool shank remains secured in the tool holder. Indexable tools do not require loosening during indexing, and as you can imagine, become the tool of choice for many CNC grinding operators.