Tool selection help

[Schulze]

I am still in tech school for CNC, all I have to go is CAD/CAM and lathe programming.

I am working on a personal project that requires a G2 on the XZ axis for a mating surface. The radius is about .6275 and another on the line of a 4.0 radius.

I am confused on the proper Ball end mill I need to select. I have never worked with a ball end before and am not sure if there are any rules of thumb for selecting them.

The application is for mild hardened 4140 steel about 25 RC. I am planning on a 1/2 4 FL EM Carbide.
Quick and dirty drawing here


What I am worried about is the back end of the radius on the EM draging and giving a bad finish.

Any help with this?

[HuFlungDung]

Was that drawing too big for this forum? I need to get an idea of the shape you are working within. A simple surface model would be adequate

But generally, your question would be answered by this: ball mill toolpaths are calculated from the center of the ball radius, not from any point on the circumference. This is contrary to using a flat ended mill, where the Z datum of the cutter is on the bottom plane.

[Schulze]

the picture is very small. but I dont know why it is not showing up.
http://www.villagephotos.com/viewpub...sp?id_=7375069
there is the address for it in my album


In a vise the bottom of the part is the side being cut. I basically just need to dish out the radius for the mating surface to another part.

I understand about calculating from the center of the nose and working off that.

Thanks for the help.