I have a single insert Carboloy bull nose (D-0.98 R-0.78) style I use for roughing bulk material out for molds. The mill chatters a little as it is single flute but it is tolerable. A good hold of the part is a must. It is very good at removing the bulk material but I would not use it for finishing. I cut 7075, 6061, and 2024 with it.
For final finishing we use .25 or smaller ball mills. The details on the molds are small down to 1/16 ball mill. There are no indexable ball mills that small.
If you cut a lot of contours you might be able to get away using a indexable ball mill. You need to look at the types of indexables. Do you need a copy mill type (with round 'button' inserts), 2 fluted slot insert ball mill (flat disk with opposing edges), or a special radius ball mill with mulitiple contoured inserts.
If you can program for the chip thinning effect of ball mills you can get a good finish with the right insert. If you are not going to take the time to program for the indexable ball mill, then do not buy it. If you plan on cutting the same materials all the time this helps because you know how it is cutting and you do not need as many insert grades.
One last thing. Coolant/fluids definitely help. Make sure you have the spindle speed to support indexable inserts.  |