Metric threads of the International Standards Organization (ISO) have the same 60-degree thread form as UN threads, though the diameters and pitches are not interchangeable. Metric tap drill charts have the same drill size problem in that they use the same formula as that employed for the obsolete AS threads. In both ISO and UN thread series, having a range of useful drill sizes allows designers and machinists to tailor effective thread depth for long holes, various materials and thread strength requirements. It also allows for the combining of inch and metric taps and drills where convenient to do so.

Many variables affect the performance of threaded holes and the taps used to generate them. One very important factor is the drill size used to produce the hole that will be tapped. Most tap drill charts call out only one tap drill size, and that will produce an approximate 75 percent thread. In general, tap tool life can be increased significantly by using a lower percent of thread and we suggest using values between 60% and 70% for most applications. Thread strength is not directly proportional to percent of thread. For example a 100% thread specification is only 5% stronger than a 75% thread specification but requires 3 times the torque to produce.

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Premium solid carbide end mills bring unmatched cutting performance, long tool life and high process security to demanding parts production in industry segments such as aerospace, medical, mold and die, and power generation.The high quality, low cost production advantages of these end mills come as a direct result of dedicated micro-grain carbide structures, optimized flute lengths, specialized edge honing and wear-resistant coatings.