![]() ![]() It is important to realize thread strength is not directly proportional to per cent of thread. ![]() By increasing the pre-drilled hole diameter, the machinist can increase the life of the tap by reducing the amount of force required to form the thread. Many tool manufacturers suggest using a percentage of thread values between 60 and 70 per cent for most pre-drilling applications. Making the correct tap drill size choice will affect the machining operation. High speed drills typically cut larger actual hole sizes than carbide drills. Many tap drill holes are now being created with high performance carbide drills and these carbide drills generate more accurate holes than high speed steel drills. ![]() Another reason why some tap drill charts are outdated is that most drills for producing tapped holes were high speed steel or cobalt when the charts were created. The percentage of thread values that older tap drill charts provide is higher than needed in most cases. To reduce the risk of thread failure, the design engineer was often cautious and specified high percentages of thread height in tapped holes. Not intentionally of course, it is just that most machinists are using outdated charts designed back in the 1950’s when high speed drills were the norm. One of the most common mistakes a machinist makes when tapping a hole is using the wrong size drill. Are you really getting the best results from your taps? Avoid common mistakes. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |