What is the best procedure for milling a .375 +/- .005 wide x .125 +/- .005 deep slot?

The best procedure for milling a .375 +/- .005 wide x .125 +/- .005 deep slot is to use a combination of a .250 diameter end mill and a .375 diameter end mill. The rationale behind this method centers on achieving precise dimensions while maintaining a smooth finish and avoiding excessive tool strain.

By first using the .250 diameter end mill to remove the bulk of the material and create a slot that is approximately .100 deep, the operator can ensure that the cutting forces are manageable, which minimizes the risk of damaging either the part or the tool. Once this preliminary milling is completed, the .375 diameter end mill can be employed to finish the slot to the desired depth of .125. This two-step approach provides better control over the dimensions and leads to improved surface quality as the larger end mill smooths out any irregularities left by the smaller one.

In contrast, milling with a single .375 diameter end mill to full depth could potentially lead to issues with tool deflection or overheating, as the cutter might encounter excessive cutting forces while trying to achieve the listed depth in one pass. Similarly, using a .500 diameter end mill does not align with the desired width of the slot, which may compromise both the tolerance and the fit of the