Bottoming Taps are for hand and machine operation and commonly used in smaller shops or DIY that prefer “one tap fits all” approach. It is a High Speed Steel (HSS) industrial quality straight flute tap made for Alpha Features / Benefits: The straight flute is the standard style of tap and is available in 3 types: Taper Intermediate and Bottom all 3 are suitable for a range of different tapping applications. As this basic tap will give acceptable performance in most materials and for medium sized production runs it is usually the most economical tap to use. It can be especially beneficial when cutting short chipping material such as cast iron. A straight flute tap can be used in through or blind holes. To determine the TPI of a screw you simply count the number of threads contained within an inch of length. If the screw is less than an inch count upto ½” and x by 2 Difference between UNC v BSW Threads: UNC and BSW have the same thread per inch value except for the 1/2" size. Theoretical it would be possible to interchange them as they have the same amount of threads per inch. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person and Bolt and Nut Australia is not responsible for any loss claim or damages arising therefrom.