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Micro End Mill Geometry

Micro End Mill Geometry

The smaller the diameter, the tougher to manufacturer

Isn’t it interesting that the smaller the end mill diameter the higher the price? There is a reason for that, micro diameter end mills are a breed of their own. The smaller the diameter the more precise you need to be. The tolerances are tighter making the level of difficulty greater. They also require special CNC grinding machines dedicated solely to the micro focus with some machines limiting the largest diameter to .080”. These machines require the tightest of tolerances, extreme accuracy, as well as temperature and vibration control. The manufacturing that goes on inside of these machines is done in much tighter quarters than compared to the CNC grinding machines made to manufacture end mills up to and over 1” diameter.

So what is it exactly that determines a good end mill from a bad one? You would think that since most manufacturers have access to the same CNC grinding machines, the same programming software, the same grinding wheels, etc, that one end mill can’t differ all that much from the next… right? After all, look at all the differentiating factors you can specify when ordering. We can specify the diameter size, end shape, number of flutes, length of cut and overall length. We can specify geometry for the type of material we are milling, we can order variable helix and index, we can even order with different tool coatings for our particular application. Unfortunately the factors that the average consumer has control over only scratch the surface of the decisions that are made during the manufacturing process. What most people don’t realize is that there are up to 21 different attributes and geometric decisions made during the end mill manufacturing process. This goes for micro diameters down to .001” up and to diameters over 1”. Each attribute has its own set of variables leaving the combinations that can be created on one particular size end mill far too numerous to count. However by industry standards just about all variations can be considered acceptable or “within end mill tolerance”. But just because some of these variation can pass inspection, doesn’t mean they should pass inspection.