Machining Threads – The ‘Do's & Don'ts's!

When it comes to machining threads, that little bit of extra expertise always comes in handy – here is a brief look at the five questions you should ask yourself when undertaking this complex piece of machining

- Kruti Bharadva

There are many elements to consider when threading a workpiece. When is a solid carbide thread mill better than an indexable? How does the workpiece material behaviour impact thread milling? Understanding your program as well as diagnosing issues that arise are just as important. Luckily, thread milling can be better understood by asking five specific questions.

WHEN WOULD YOU WANT TO USE A 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 cases, this comes back to one common issue: taps break. Because the tap is the same size as the hole, there is a lot of pressure when you 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 the factors 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.