| |JUNE 202119FIVE QUESTIONS TO ASK WHEN MACHINING THREADSThought CentralBy Jamie Rosenberger, Senior Product Manager, Allied Machine & Engineering CorpT here are many elements to con-sider when threading a work-piece. When is a solid carbide thread mill better than an indexable? How does the workpiece material be-havior impact thread milling? Under-standing your program as well as di-agnosing issues that arise are just as important. Luckily, thread milling can be better understood by asking five specific questions.WHEN WOULD YOU WANT TO THREAD MILL INSTEAD OF TAP?There are many instances where you would want to consider using a thread mill instead of a tap. In numerous cas-es, this comes back to one common issue: taps break. Because the tap is the exact same size as the hole, there is a lot of pressure when you are are forcing the threads into the hole--even more so in difficult-to-machine materials. Additionally, a tap's cutting edges are constantly in the cut, thus generating more heat. A thread mill on the other hand has little contact with the material, and the heat generated is much lower--an added benefit in any manufacturing process. Finally, when using a tap, chips are more difficult to form and remove.All of these things mentioned above lend themselves to tool failure. When the tap breaks off, it often results in a scrapped part, so using a tap works better when it is an inexpensive part being made. If it is a more 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 diam-eter. Of course, a tap is just as large as the hole, so for a four inch thread di-ameter, 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. Last-ly, 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 toler-ances 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 exam-ple, 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 appli-cations, 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. WHEN SHOULD YOU USE SOLID CARBIDE THREAD MILLS VS. INDEXABLE THREAD MILLS?In choosing to thread mill, you have Jamie Rosenberger
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