Picking the Correct Material Substrate for Tapping
Like most cutting tools, taps can be manufactured from a variety of material substrates. Generally, these materials can be broken down into a good, better and best system. The materials break down as follows: High Speed Steel(Good), High Speed Cobalt(Better), Powdered Metal(Best). The natural inclination may be to use the best material(powdered metal) as who wants to use something inferior when you can have the best. This mindset does not always lead to the most efficient or most economical outcome. The following are some advantages to each material substrate:
High Speed Steel(Good)
This is generally the least costly tap to purchase. High speed steel is the workhouse of tapping, especially for low run volume jobs. High speed steel will lack tool wear versus high speed cobalt and powdered metal. However, high speed steel is more shock resistant than the other materials which means it is less prone to chipping. If you have some alignment issues with your tapping application, high speed steel may be the least expensive tap per hole as it will not chip before it wears to the end of its useful life.
High Speed Cobalt(Better)
High speed cobalt is often the best choice for tapping. Because it is harder than standard high speed steel it offers more wear resistance. This wear resistance leads to longer tool life which means more holes being tapped before a tool change is required. Generally, high speed cobalt is slightly more expensive than high speed steel but the extra tool life more than often makes up for the higher purchase price. The one drawback of the harder material is that it is more prone to chipping. If you have alignment issues then these taps may chip before they wear out which minimizes or eliminates the advantages it has for cost per hole being tapped.
Powdered Metal(Best)
Powdered metal taps tend to be used for specialty type of applications (i.e. tapping stainless steel or exotic metals). Often times these may be the only taps that will tap some of these materials. These taps are often 2-3 times more than either high speed steel or cobalt. Often times, these taps can be overkill when tapping some general mild steels, aluminum, etc. In fact, while tap life in exotic materials may be excellent, tool life in some of the milder materials may not far surpass that of high speed cobalt.
