22. Features of MC-Helical Thread Mills Description of products Metric thread Metric thread [ Minor dia. basis] [ Tool basis] Tool cut Tool transverse where, : Nominal size of internal threads : Basic minor diameter of internal threads : Minor diameter before cutting : Outside diameter of tool : 0.866025P : Pitch : Tolerance of pitch diameter for producing internal thread : Shrinkage after cutting (Set up in the middle of pitch diameter tolerance) : Difference between of basic thread profile and O.D. of the cutters. ■Approaching and leaving to and from work material On approaching and leaving to and from work material, the cutter must always be traversed in helical interpolating movement so that the cutter enables smooth cutting in and out. And it is necessary to cut the material gradually by the lead of screw thread. Otherwise, threads can be thinned. Initial cutting A B Technical Information Technical-67 838