So I've got a job that uses a 0.250" thick, 0.040" double corner radius, 1.75" OD, 1/2" shank (with a small relief due to the depth of the feature) slot mill / keyseat cutter, whatever. 14 tooth, solid carbide. It is cutting 4140 at 41-44HRc. It goes in fine but then hits a cross hole and...