Page 156 - Demo

154 ISCAR PRE-THREAD DRILLING WITH CHAMFERING Pre-Thread Drilling / Drilling with Chamfering Drilling Stepped HolesA large number of drilled holes require chamfering. In some cases, the profile of the required hole is more complex and includes chamfering and counterboring. A preparatory hole for threading is one of the common uses for these holes. Despite the fact that cutting internal threads is not a complex technological operation, there are some features for the preparation of this procedure. In most cases, before threading, it is necessary to drill a pre-hole with a chamfer. Sometimes counterboring is also required in addition to chamfering. Therefore, it is recommended to accurately determine the dimensions of the pre-hole for threading and choose the right tool, for which special tables of drill diameters for threading are used. For each type of thread, it is required to use the appropriate tool and calculate the diameter of the preparation hole. Keep in mind that if the diameters of the pre-holes intended for threading are chosen incorrectly, this can lead not only to poor quality threads but also to breakage of the threading tool. An additional example of the use of holes with chamfering, or holes with chamfering and counterboring, are holes for screws, rivets, etc.Hole with Chamfering Hole with Chamfering and CounterboringCommon UseDeburring VPreparation for Threading V VFlush Fastening for Bolts,Screws, Nuts, Etc. V VReduced Stress Concentration VBushing Placement V VCosmetic Enhancement V V