Thread milling tool

Why thread milling? 

Thread milling is a modern threading method used on CNC machines where a helical interpolation strategy is employed to generate both internal and external threads. Compared to traditional tapping, thread milling offers: 

• Lower risk of tool breakage 

• One tool for multiple dimensions and pitches 

• Better control over thread quality 

• Efficient chip evacuation – especially in blind holes 

• Suitable for hard-to-machine materials like titanium or Inconel 

The STS ThreadMill™ program – an overview 

The STS ThreadMill™ product line offers a comprehensive range of indexable thread milling tools designed to support metric and inch threads, including: 

• ISO Metric 

• UN/UNJ 

• Whitworth (BSP, BSPT) 

• Trapezoidal, ACME, NPT/NPTF, API, STI and more 

Our thread milling inserts are available in several coated and uncoated carbide grades, optimized for performance in different materials. The indexable tool bodies are available in solid carbide or steel, and support: 

• Radial or axial coolant channels 

• Internal or external thread profiles 

• Right- and left-hand threads with the same tool 

STS also offers customized tools upon request — ideal for special thread profiles or uncommon dimensions. 

Key features and benefits 

Multi-profile capability

One insert can be used for various thread pitches and diameters, reducing tool inventory and changeover time. 

Replaceable cutting edges

Indexable inserts mean lower long-term costs — just replace the insert, not the entire tool body. 

Optimized coatings and grades

Choose from a range of carbide grades such as STN20 and STN50, or coated options like STN50X, to match your material and application. 

Support for multiple standards

Whether you’re working to ISO, ANSI, API, or DIN standards, STS ThreadMill™ supports them all. 

Excellent documentation and support

Our technical guide includes cutting data, thread tables, and recommended programming strategies. 

How to choose the right thread milling tool 

When selecting your thread milling tool, consider: 

1. Thread profile and standard 
2. Thread size and pitch range 
3. Workpiece material 
4. Coolant requirements (internal/external) 
5. Machine capability (helical interpolation, spindle speed) 

STS provides a full compatibility matrix and support in selecting the optimal tool-body and insert combination. 

Programming and application tips 

Thread milling requires some adaptation in your CAM strategy — but offers flexibility in return. Best practices include: 

• Use climb milling for better surface finish and tool life 

• Ensure proper lead-in and lead-out movements 

• Adjust RPM and feed rate based on material and tool diameter 

• For internal threads, use tools with radial coolant to flush chips efficiently 

STS’s guide includes G-code examples and data tables, making implementation faster and safer. 

Tool life and productivity 

Thread milling tools from STS are built for longevity and repeatability: 

• Inserts can be indexed and replaced, extending the tool body’s lifespan 

• Tools are balanced to minimize vibration and ensure accurate thread form 

• Optimized geometries reduce cutting forces, especially in high-temp alloys 

Compared to tapping, total cost of ownership (TCO) is lower over time — fewer tool changes, less scrap, and better surface finish. 

Ready to optimize your threading process? 

Whether you need to machine high-precision threads in exotic alloys or want to reduce tooling complexity in your shop, STS ThreadMill™ delivers. 

Contact Scandinavian Tool Systems today to speak with a threading expert or request a tailored quote. 

Let us help you take control of your threading operations — with precision-engineered solutions, ready for the most demanding jobs.