The approximate hole sizes set forth on the following pages are intended to provide general guidance to the user in selecting holes for installing the respective types of thread forming and thread cutting tapping screws in various commonly used materials. It should be noted, however, that because conditions and considerations having a bearing upon screw applications
differ widely, it may be necessary or desirable to vary the hole from the specified size to best suit a particular application. Refer to Para. 1.5.1 in the Introductory Notes, page G-39, for further explanation of some factors which affect assembly torques.