Working on these somewhat complicated parts, I got to program yesterday.
There are three L-shaped pieces, and I'm doing them all together in a large piece of bar-stock. Unfortunately, I had to run through a somewhat tedious process of removing the material around it before I could finish the sidewalls and get the small details because of their shape.
Because these parts have such high walls and tight corners (see my previous post), I had difficulty getting good surface finishes. I'm actually a little surprised how well the 1/4" long flute endmill did cleaning the sides at multiple steps. We don't have a tool long enough to get the entire depth of the wall in one shot, so my boss reduced the tool's neck so I could take it at several stepdowns. I would previously have issues where there would be a witness mark showing where the end of the flutes ended and the endmill's neck started; this time, there wasn't!
The difficult feature of this part is the corner where the two inner lines meet up. They have a hole in that corner to ensure the block that gets set into it is perfectly square to the two side walls. Unfortunately, this means that cleaning the inner walls has to be done with a small endmill which chatters more the longer the tool sticks out. I was able to clean up the majority of the wall surface with a 1/4" SQ, but as it got close to the corners, there was a very slight hook where the tool couldn't quite make it. Because of this, I had to take a very long reach 1/8" sq and take very slow cuts (low rpm and feedrate) to make sure that back corner was square.
The problem with this is that because you are using two different endmills to clean the same surface, it's nearly impossible to get a seamless transition due to the actual diameter of the tools you're using. Because of this, I had to guestimate the actual diameter of the 1/8" and compensate for the offset by leaving negative stock to leave on the side walls. It's not perfect, but I was able to slightly undersize the sidewall by 0.0003" (3 tenths) which is acceptable for this part so long as it's not positive). You can see in the image above the faint difference between 1/4" and 1/8" sq endmills.