How Thread Milling Works

What is Thread Milling?

Thread milling is a way to make threads. Threads are the spiral lines on screws and bolts. When you do thread milling, a spinning tool moves in a circle and goes up or down at the same time. This makes the threads. Unlike tapping, where the tool is the same size as the hole, thread milling uses a smaller tool that moves in a spiral path to cut the threads. You need a machine to do thread milling. The tool spins fast and cuts the metal bit by bit.

Thread Milling vs. Tapping

Thread milling and tapping are not the same.

Tools:

• Taps are the same size as the hole
• Thread mills are smaller than the hole

How They Work:

• Taps push into the hole and make threads
• Thread mills spin and move in a spiral to cut threads

Good Things About Thread Milling:

• One tool can make many thread sizes
• Uses less force on the metal
• Better for hard metals like titanium
• Chips come out more easily

When to Use Tapping:

• For small, simple threads
• When you need to work fast
• For soft metals

Thread milling is best when you need to make custom threads or work with hard materials. For easy jobs on soft metal, CNC threading with taps might be better.

How Thread Milling Works: Step-by-Step

1. Pick the Right Tool

• Use carbide tools for long life
• Make sure the tool matches the thread size you want

2. Set Up the CNC Program

• Write the G-code for the spiral path
• Set the right speed for the metal type

3. Get the Work Piece Ready

• Hold the part very still in the machine
• Drill a hole to the right size first

4. The Cutting Motion

• The tool moves in a spiral path
• All three axes (X, Y, Z) move at once
• Don’t go too deep (no more than 1.5× the hole size)

5. Finish Up

• Smooth any rough edges
• Check the threads to make sure they’re right

Good Things About Thread Milling

Thread milling has many benefits:

• Makes very exact threads (up to ±0.001 inch)
• Can make inside or outside threads
• Can make left or right hand threads
• Works on hard metals that break taps
• One tool can make many different sizes

This makes thread milling great for precision CNC machining jobs where you need very exact threads.

Where Thread Milling is Used

Thread milling is used in many places:

Planes and Space

• Makes strong threads for engine parts
• Used for titanium parts that break taps

Medical

• Makes tiny threads in implants
• Very clean threads for surgical tools

Cars

• Custom threads for new designs
• Strong threads in engine blocks

Oil and Gas

• Big threads in pipes
• Threads that must not leak

Thread milling is best for jobs that need exact sizes or special threads. When doing prototype CNC milling, thread milling gives you more options.

Thread Milling Facts and Numbers

Tips for Good Thread Milling

To get the best threads:

Stop Tool Bending

• Use short tools for deep holes
• Don’t go too deep at once

Find the Right Speed

• Slower for hard metals
• Faster for soft metals
• Balance speed and tool life

Use Coolant

• High-pressure coolant keeps things cool
• Helps get chips out of the hole

Take Care of Tools

• Check tools for wear
• Replace dull tools before they break

Common Problems and Fixes

Sometimes things go wrong. Here’s how to fix them:

Rough Threads

• Tool might be dull
• Speed might be wrong
• Try a slower feed rate

Threads Not Lined Up

• Check the CNC program
• Make sure the part isn’t moving

Chips Getting Stuck

• Use air or coolant to blow chips away
• Try a different tool path

Questions People Ask

Threading Tool Types

There are a few types of thread mills:

1. Single-profile mills – Cut one thread at a time
2. Multi-profile mills – Cut many threads at once
3. Thread form mills – For special thread shapes

The best type depends on what you’re making. For custom CNC machining, single-profile mills give you the most options.

Why Choose Thread Milling?

Thread milling is best when:

• You need exact threads
• You work with hard metals
• You need to make many different sizes
• You can’t have a broken tap stuck in an expensive part
• You need special-sized threads

For shops that do many kinds of jobs, thread milling gives you more options with fewer tools.

Materials for Thread Milling

Thread milling works on many materials:

• Aluminum – Fast and easy to mill
• Steel – Needs slower speeds
• Titanium – Hard but thread mills work well
• Plastics – Need special speeds to avoid melting
• Stainless Steel – Needs good coolant

When doing titanium CNC machining, thread milling is often better than tapping because taps break easily in titanium.

Thread Milling on Different Machines

You can do thread milling on:

• 3-axis CNC mills – Most common
• 4-axis CNC mills – For complex parts
• 5-axis machines – For threads at odd angles
• CNC machining centers – For making many parts

Most CNC shops can do thread milling, but the more axes the machine has, the more complex the threads it can make.

The Future of Thread Milling

Thread milling keeps getting better:

• New coatings make tools last longer
• Better software makes programming easier
• New tool designs cut faster and smoother
• Hybrid tools can both drill and thread mill

As CNC machines get better, thread milling will be used more and more for parts that need exact threads.

Conclusion

Thread milling is a great way to make threads. It uses a small, spinning tool that moves in a spiral path to cut threads in holes or on rods. Unlike tapping, thread milling:

• Uses less force
• Works on harder metals
• Can make many thread sizes with one tool
• Makes very exact threads

For jobs that need special threads or work with hard metals, thread milling is often the best choice. Thread milling is used in planes, medical tools, cars, and oil rigs – anywhere that needs strong, exact threads.

If you need to make threads in hard metals or need very exact threads, thread milling is a great option to look at.