What is the recommended procedure for milling a 0.375 ± 0.005 wide X 0.125 ± 0.005 deep slot?

Using a 0.250 diameter end mill followed by a 0.375 diameter end mill is a recommended procedure for milling a slot that is 0.375 ± 0.005 wide and 0.125 ± 0.005 deep because it ensures precision in machining the slot dimensions while managing the tooling and forces involved in the milling process.

Starting with a smaller diameter end mill allows for more controlled cutting. It reduces the amount of material removed in one pass, which minimizes the risk of tool deflection and helps maintain dimensional accuracy. This first pass can create a rough profile of the slot, which the larger end mill can then clean up on the second pass. The 0.375 diameter end mill will provide the final cut to achieve the desired width, ensuring that the slot meets the specified tolerances.

This graduated approach also helps in achieving better surface finishes and is less taxing on the tooling. It is common practice in machining to use multiple tool sizes to reach desired dimensions, especially in cases where tolerances are tight and precision is essential. Thus, this method effectively balances efficiency and precision.