Machinist Apprentice | Steep Machining Depths | Day 163

Working on a new set of parts that pose a very subtle but interesting challenge.

One of these pieces' requirements is that you can't use any sandpaper or Scotch Brite to finish up the parts' surface due to their final use. This wouldn't normally be an issue; however, many steep walls lead into tight corners on this job. They are all L-shaped, and the parts' outer contour is no big deal, and I can use large endmills for it. However, since they have an inside corner that needs to be pretty sharp, I have to use a smaller endmill. 

In one section, the wall spans nearly 1.5," and I have to somehow get an 1/8" endmill to finish the walls without any burnish marks from the shank. The solution to this problem is using a combination of a 1/4" endmill to finish the majority of the surface, then come in with a reduced shank cutter and get the remaining spots the 1/4" couldn't reach. 

One problem may arise, which is the diameter of the tools themselves; when endmills are ground down, they are typically undersized vary slightly from their written size. To fix this problem, I will be using tool cut diameter compensation (CDC) inside the machine and program to sneak up on the correct size. 

For example, say you cut a square block with a 0.5" endmill, and you want the block to be 1" square. When you cut and measure it, you find it's actually 1.008". You would then input into the diameter offset -0.004" (0.008/2), and the toolpath would adjust to compensate for the offset. Most of the time, this isn't necessary as the difference is so slight it falls into most tolerances. But in this case, where the wall's surface needs to be clean and accurate, I will have to make sure it's as close as possible.