Tips for thread milling coarse pitches

Optimising thread milling

Thread milling has become quite popular in recent years as an alternative to tapping or other forms of threading because of the diversity and complexity of parts including flexibility of the process in industries, such as biomedical applications, aerospace and die-mould manufacturing. It continues to  develop with further applications being added to an already productive method of machining.

With the constant development in CNC machining centres and the resulting expansion in sales of these machine tools, manufacturers now have great opportunities to reduce manufacturing costs.  Most machine centres are designed for applying helical interpolation (an essential feature for thread milling) in both clockwise and counter clockwise directions, so that left and right hand threads can be machined with the same cutter.

Development in software aids to programming take the uncertainty out of the decisions to use thread milling as a key component, not only to reduce the direct cost of producing threads but also significant costs in unnecessary handling and set up costs.

Still today, tapping many types of hole is fraught with problems, the biggest of these being the potential risk of scrap or rework should the tapping operation result in breakage of the tap or due to wear and the thread is undersize. The flexibility of the thread milling operation with indexable inserts eliminates these potential problems entirely.

Advantages of thread milling

? Short cycle times due to rapid feed rates and high cutting speeds

? No thread relief groove needs to be machined, thus saving an unnecessary operation

? For a given set of tooling, there is no limit to the maximum bore diameter that can threaded.

? complete machining can be finished in a loading up thus eliminating costly set up charges

? the same toolholder can be used for both internal and external threads

? The same insert can be used for both left hand and right hand threads.

? Inserts are interchangeable, if it is necessary to replace an insert there is no need to reprogram the machine tool.

? In the case of BSW, BSP, BSPT, NPT, NPTF the same insert will produce both internal and external threads.

? Since a small range of tooling covers a very wide range of applications, the amount of money tied up in stock can be significantly reduced.

? The quality of the threads have a high surface finish

?  The technique is suitable for machining hard materials.

? Chips are always short, thus there are no problems in chip control.

? Threading of large diameters requires no extra horse power compared to smaller diameters.

?  Due to very low cutting forces, components with thin walls can be machined without risk of  component distortion.

? As wear takes place on the insert, compensation in the program can be carried out without any waste of time.

What is helical interpolation?

The pre requisite for generating a thread form with a thread milling indexable inserts is the CNC machine tool function for guiding tool movement along a helical path.

Helical interpolation creates a tool movement in a helical path from point A to point B on the surface of an imaginary cylinder. This helical path involves the simultaneous movement in axes X, Y, and Z.Air Huarache Classic