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What is thread milling and how thread milling cutters work

Thread milling is a versatile and practical thread manufacturing solution and CNC machining process, especially for large holes. This process tends to be used primarily for many applications rather than tapping. What are the advantages of thread milling? In this guide, we will discuss what thread milling is, its applications, benefits, types of thread milling tools, how thread milling cutters work, and how thread milling cutters work.

What is thread milling?

Thread milling is a metalworking process that cuts threads of different sizes through the circular ramp motion of a rotating tool, and the thread pitch is generated by the lateral motion of one revolution. Unlike tapping, thread milling is mainly used for large workpieces. However, solid carbide thread mills can also machine small threaded holes. The same machine can process left-handed and right-handed threads at the same time, different thread tolerances, different materials and hole diameters, and produce threads with high precision and good surface finish. While not as widely used as thread turning, thread milling can be highly productive in some applications.

Advantages of thread milling

– Thread milling can cut threads on difficult-to-machine materials.

– It is a safe machining operation and is easier to perform on the machine tool.

– The process reduces machining time and saves energy.

– The tool is flexible and the same tool can be used to produce right-hand or left-hand threads.

– Thread milling allows machining of very shallow blind threads in the thinnest materials over very short distances.

– It achieves high thread quality without burrs.

– Reduce wear on machine spindles.

– Can be used on lathes with live tools.

– Immediate correction of the thread diameter.

– Use a tool that is smaller than the thread to ensure correct threading with the clearance needed for chip evacuation.

– There must be a hole of the right size.

Thread milling cutter

A thread mill is a tool designed to cut threads by milling. Different thread milling cutters or cutters can produce threads from internal to external, medium to large sizes. Thread milling cutters can be used on CNC machining centers with synchronous, three-axis control and helical interpolation functions. Thread milling with solid carbide thread mills or steel shanks with indexable inserts.

Solid carbide thread milling cutters: for smaller hole sizes, more expensive than indexable cutters, but can be cost-effective depending on the quality required.

Indexable insert thread milling cutter: not suitable for holes with a diameter of 15 mm or less. Once the thread mill body is ready, the cost of producing the threads is only to replace the inserts.

How does a thread mill work?

The thread milling process can use a helical interpolation toolpath instead of tapping. The thread milling cutter looks similar to a tap, but the effect is different. Insert the thread mill into the hole along the axis of the spindle until it is deep enough to produce the desired full thread depth, the controller moves the thread mill to the hole diameter and cuts the thread into the hole sidewall,

Then perform a 360° circular motion and return to the starting position. When the thread milling cutter makes a circular motion, it needs to move to the top of the hole or move a pitch along the Z axis of the machine tool to process the thread. The depth of the thread is usually no more than one and a half times the diameter of the hole to minimize deflection.

When to Use Thread Milling - Thread Milling Applications

Thread milling is the correct process for the following applications or requirements:

– Thin-walled parts

– Asymmetric/non-rotating components

– The processed material produces high cutting force, which is easy to cause chip removal problems

– Need to reduce tool inventory

– Unstable component setup

– as an alternative to tapping

– To adjust the tolerance of thread

– Cut multiple odd thread sizes with one tool

– Back chamfering the hole

Thread Milling vs Tapping - What is the Difference Between Thread Milling and Tapping

Compared with tapping, which process should you choose?

– Tapping is generally used to create threads in small holes after drilling, whereas thread milling tends to create threads in larger holes.

– Tapping uses a tool that is the same size as the thread, forcing chips to escape through the thread, while thread milling uses a tool that is smaller than the thread, so thread milling achieves better thread quality than tapping.

– Tapping can be done by hand or by machine. Thread milling typically requires a CNC machine with at least three axes for helical interpolation.

– Thread milling requires lower cutting forces than tapping.

– It is not necessary to have the correct hole size during thread milling, a single tool can be used in thread milling to machine holes of various sizes. With tapping, each hole that needs to be tapped requires a different size tap.

– Thread milling allows for easy machining of pipe threads without troublesome filamentous chips during tapping.

– Thread milling can achieve better thread quality and smoother surface than tapping

– Thread milling enables users to design custom threads, which can be very expensive and require long lead times.

– Tapping does not allow adjustment of thread fit. Once the hole is tapped, the size and location of the threads are fixed. Whereas thread milling can control the fit. Machine operators can adjust the thread size using a strategy similar to drilling with an end mill instead of a drill.

Thread Milling Guidelines and Tips

1. Choose the right quality tool

High-quality and suitable thread milling cutters are essential to avoid failures and problems during machining, you can choose some qualified tool manufacturers and compare their advantages and disadvantages, and then choose the one that is closest to your requirements. Before that, you need to master the types of thread milling cutters (oblique flute thread milling cutter, straight flute thread milling cutter, single tooth thread milling cutter, indexable insert thread milling cutter, solid carbide thread milling cutter, etc.) and these Specifications for thread milling cutters (single edge thread milling cutters). shapes, trimorphs, and polymorphs), such as diameter.

2. Apply several radial channels

Dividing the thread milling operation into multiple radial passes results in higher quality, improved thread tolerances, safety and tool breakage when machining difficult-to-machine materials, and makes it suitable for difficult applications such as long overhangs and unstable conditions.

3. Select chip breaking and chip removal strategy

Appropriate tools or strategies should be used for chip breaking and chip removal in a timely manner. Cutting fluids and lubricants can be considered to avoid chip recutting, save time, and ensure thread tolerances.

4. Determine the tool path

Left-hand or right-hand thread depending on the selected toolpath. Which one is more suitable for you? Choose the more effective one based on your experience.

5. Thread depth

Generally, the thread depth should not exceed one and a half times of the hole diameter. Because the longer the cutter, the more likely it is to deflect, which can lead to inaccurate threads.