[broderi]

All,

I wanted to run something by a group of knowlegable folks on a part that we are trying to make here.

We have a chain link to make, out of 4340 steel, and we plan to do it by using the GibbsCAM Solid surfacing package and a long program that steps a ball nose cutter over the profile.

The chain link is about 3" dia steel, and measures about 23 in by 13 in out to out.

I have some experience with surfacing on weird curves, but only with alu and plastics. Wondering how it works with steel.

[cadman]

I machine lots of hardened 4340. You don't want to plunge into the material. When necessary, use helical or ramp entries (closed pockets). I use drill entries as little as possible because I tend to use as few tools as possible. Plunge roughing could also be the hot ticket for you depending on the tool you use. Standard endmills work ok but may not be long enough and dont last that long when plunge roughing

Whenever possible, rough with a flat bottom endmills and radius corners. Coated HSS fine pitch roughers (Niagara, Hanita) work very well for roughing and you can make some fairly large cuts. For semi-fininshing and finishing use carbide endmills. Obviously feeds & speeds are different than aluminum and plastic, and you won't be making the same depths of cut or stepovers. Most of your cuts should be in the climb direction.

4340 actually cuts very nice and I prefer to cut it in the hardened state.