by: Matthew Viau on Oct 15, 2015
A 0.5" endmill fits in a 0.25" corner radius right? The answer is sort of. When designing any internal feature, the largest allowable corner radius is the best, within reason of course. A 1" radius is not necessary on a 0.25" dp pocket, but as a rule of thumb the pocket should not be any deeper than three times the cutter dia. This doesn't mean that you can't have deeper pockets or smaller radii, but it does start to get rather tricky when the depth to cutter diameter ratio exceeds five. Another basic rule is that the radius shouldn't match the cutter perfectly. In the examples below you can see that the rightmost pocket allows the cutter to interpolate along the radius instead of ramming straight into the corner like the center example. The best way to avoid this is to open up the radius just a little bit. A 0.500" end mill would fit fine in a 0.270" radius. Even a 0.255" radius would be better than an exact radius.
TL;DR - If possible the radius of an internal corner should be bigger than the cutter intended to make it, and similarly the pocket should be no deeper than five times the diameter of the cutter intended to make it.
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