Page 51 - CNC West Oct-Nov 2021

expensive part and the tap breaks, you are now faced with the challenge of trying to remove the tap and salvage your part. This is a time consuming operation that impacts your part’s quality and manufacturing cost.
Not only would you want to thread mill whenever the part is expensive, but you would also want to thread mill when working with a large hole diameter. Of course, a tap is just as large as the hole, so for a four inch thread diameter, you need a four inch diameter tap. Instead of buying this expensive, large piece of metal or storing
taps for every thread size, you could buy an off-the-shelf thread mill and interpolate the thread into multiple thread sizes including those large diameters. Lastly, thread mills consume significantly less power from your machine in the instance of large diameters.
Other advantages of thread mills include the ability to hold tight tolerances by controlling the tool’s cutting path. As the tool shrinks slightly from wear, you can easily compensate this at the machine by using tool diameter offsets.
Nevertheless, there are occasions where tapping may be the better choice over thread milling. For example, you would want to use a tap when machining long lengths of thread. Due to the lack of radial load, there is no concern about the tap’s stability or tool deflection. In addition, when speed is preferred over thread quality, taps are again the better choice. In many applications, a tap will have a shorter cycle time than a thread mill. However, this still comes with the risk of breaking the tap and spending your valuable time to get it removed.
CNC WEST October/November 2021
www.CNC-West.com 49