Cutting Threads in Plastic – Is That Even Possible?

Plastic has long been indispensable in industry and mechanical engineering and is becoming increasingly important for DIY enthusiasts. The flexibility of the material and its high adaptability in terms of shape and properties such as weight and corrosion resistance make plastic a competitive alternative to metal for many applications.

Plastic components are lightweight and flexible, can be formed into a wide range of shapes, and can be manufactured in all kinds of colors. But plastic components also need to be connected somehow and we all know that threads always play an important role in this topic.

That is why we are addressing the question today of whether it is possible to cut threads in plastic. Which plastics are suitable for thread machining and which are not? Do you need special tools and where can you find them? And what do you need to consider when working to create reliable screw connections even in plastic components? If you are looking for answers to these questions, then keep reading and learn everything you need to know about cutting threads in plastic.

Plastic is not just plastic

The term plastic covers a wide variety of different materials. After all, the polyester jacket you wear for training is made of plastic just like your car dashboard or the acrylic glass protecting your flat-screen display. You cannot cut threads into all of these items and even where it is theoretically possible, you should not always do it. So let us first look at what unites the different plastics and what sets them apart.

The common element of all plastics is macromolecules that are linked together in chain-like structures. Depending on the exact composition, around 200 different plastics are created, each with a unique combination of properties that can be further modified through different manufacturing processes.

Plastics are usually divided into three groups according to their thermal properties:

• Thermoplastics such as polyethylene or polypropylene are solid at low temperatures and become soft and formable when heated.

• Thermosets, such as resins including epoxies, do not become plastically deformable when heated but can only be machined mechanically.

• Elastomers such as rubber are elastic at room temperature and do not soften when heated.

External and internal threads can be cut into many plastics belonging to the thermoplastic and thermoset groups.

These special features must be considered for plastic threads

Many plastics can be machined using standard taps and twist drills. To be safe, check the product description, which should state the materials the tool is suitable for. Whether hand taps, machine taps, or dies in hex or round design – basically, there are no limits when it comes to connecting components with threads.

The topic of heat development plays a particularly important role depending on the type of plastic. Most plastics are far more sensitive to heat than steel or stainless steel, so you should work with the lowest possible speeds when cutting threads. If the tap becomes too hot, this can impair the quality and service life of your plastic threads.

When choosing tools, you should also pay special attention to high quality and sharp cutting edges. Of course, this is always important, but when machining plastic, using high-quality drills can make a particularly big difference. Avoid using worn tools and consider purchasing a new tap for important projects.

If you follow these tips, you can proceed with thread cutting in plastic just as usual: Prepare the core hole in the appropriate size, deburr the edges or countersink them, and then create the desired thread using a tap and a suitable lubricant. Your plastic thread is finished.

More stability with thread inserts and more

Soft materials such as plastic can become problematic when a thread is frequently used, for example when a screw is repeatedly inserted and removed. Thread inserts are an excellent solution for such cases and offer many advantages.

Thread inserts are available in a wide variety of versions, diameters, and for every thread size. Compared to threads cut directly into plastic, using an insert significantly increases the load capacity of the screw connection and ensures the reusability of the thread.

Our BaerFix thread inserts are suitable for use in thermosets and thermoplastics. Their self-tapping design makes installation particularly easy. All you need to do is prepare a core hole with the appropriate diameter and install the BaerFix insert using the installation tool.

We also work closely with you in special cases and manufacture thread inserts according to your exact specifications. Contact us if you are looking for special thread inserts for various materials such as metal, plastic, or wood.

Cutting threads in plastic with threading tools from BAER

In the BAER online shop, you will find a wide range of threading tools for plastic and many other materials. Use the practical Toolfinder on our website or browse through the categories.

If you have questions, need more information, or need help finding a suitable tap for plastic, you can always contact our experienced customer service. Our staff will be happy to advise you and support you step by step with your project.