Unless you have very specific reason to make a feature a certain way you should just define what you want, include what is allowable, and let the machinist figure out the best way. For instance, will it be easier for the machinist to turn the part or the head and use a standard endmill? If using a standard endmill and expecting a circular runout then you should define a range of cutter diameters that are suitable; allowing the machinist to use a standard cutter should also allow him to use one he already will be using to make the part. Will it be easier to use a bevel cutter that he already has loaded for cutting chamfers? That is our standard method, and even then it has a runout so we model that to know what we are getting on the part.
If what you want is a chamfer to go part of the way along the edge then specify that. This CAN be machined without a runout, but if a runout is allowed then indicate how much you can tolerate such as "R.500 Max Runout Allowed". Many designers unwittingly add cost to a part by over-specifying details or manufacturing methods that do not affect the part's function. It is good to think like a machinist so that you can be sure the part CAN be machined, but if that is not your wheelhouse then effectively specifying machining methods tends to cost money. For instance, rotating the part (using a fourth axis) or the head is considered an additional setup, but a tool change to swap to a bevel cutter is very fast.
When in doubt, talk to the machinist and let him know what you are after and ask how he would approach it. Then you are in a better position to specify the right things on the print.
- - -Updraft
