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Tapped Hole vs. Threaded Hole – What’s the Difference?
Table of Contents
What is a Hole?
A hole is a round space in something. We make holes in things to put other things in them.
What is a Threaded Hole?
A threaded hole has spiral lines inside it. These spiral lines are called threads. Threads help hold screws tight.
You can make threaded holes in many ways:
- Tapping (using a special tool)
- Thread milling (using a machine)
- Thread forming (pushing the metal)
People use threaded holes in:
- Bikes
- Cars
- Tables
- Phones
What is a Tapped Hole?
A tapped hole is a kind of threaded hole. It is made with a tool called a tap.
The tap cuts internal threads in the hole. You need to make a hole first, then use the tap.
Tools for making tapped holes:
- Hand taps
- Machine taps
- Tap drills
People make tapped holes for:
- Fixing things
- Building things
- Making small batches of things
How Tapped Holes and Threaded Holes are Different
| Thing | Tapped Hole | Threaded Hole |
| How it’s made | Made with a tap tool | Made with a tap, mill, or other tool |
| Tools needed | Tap and drill | Taps, mills, or other tools |
| How good it is | Can be less straight if done by hand | Can be very straight if done by machine |
| What it works with | Best for soft metal like aluminum | Can work with hard metal like stainless steel |
| Cost | $0.10-$2.00 each | $0.50-$5.00 each |
| Time to make | 1-3 days | 3-7 days |
Making a Tapped Hole
- Drill a hole
- Pick the right tap size
- Put the tap in the hole
- Turn the tap to cut threads
- Back the tap out
- Clean the hole
Watch our CNC thread milling video →
Making a Threaded Hole with Thread Milling
- Set up the CNC milling machine
- Put in the right tool
- Program the machine
- Let the machine cut the threads
- Check the threads
Thread milling is best for:
- Big jobs
- Hard metals
- When you need very good threads
Which One Should You Pick?
Pick a Tapped Hole When:
- You need to make just a few holes
- You are working with soft metal
- You don’t have much money to spend
- You need it fast
Pick Other Threaded Holes When:
- You need to make lots of holes
- You are working with hard metal
- You need very good threads
- You have machines to help
Thread Standards
Threads come in different sizes and types:
- Metric (used in most countries)
- UNC/UNF (used in the USA)
- NPT (for pipes)
You need to know which one to use!
Common Problems and How to Fix Them
Problem 1: The tap broke in the hole
- Fix: Use a special tool to get it out or make a new hole
Problem 2: The threads are not good
- Fix: Use a better tap or go slower
Problem 3: The hole is too big
- Fix: Use a thread insert to make it smaller
Materials for Threaded Holes
You can make threaded holes in:
- Aluminum (very easy to tap)
- Steel (harder to tap)
- Titanium (very hard to tap)
- Brass (easy to tap)
- Plastic (easy but can break)
Learn about our aluminum CNC machining →
Tools for Making Threaded Holes
For Tapped Holes:
- Hand tap set
- Tap wrench
- Drill
- Tap drill bit
- Oil or cutting fluid
For Thread-Milled Holes:
- CNC machine
- Thread mill tool
- Computer program
- Cutting fluid
See our CNC threading service →
Fun Facts About Threads
- The first screw threads were made in wood in the 1400s!
- A big machine can have over 1,000 threaded holes.
- Some threaded holes are so small you need a microscope to see them.
- 5-axis machining can make threaded holes at any angle!
Steps to Design Good Threaded Holes
- Pick the right size for your job
- Make sure the hole has room for the tap
- Don’t make the hole too deep
- Add a small slope at the start of the hole
- Make sure the metal is not too hard
Tapped Holes vs. Threaded Holes: The Strength Test
Tapped holes can be 20% weaker than other threaded holes. This is because tapping cuts the metal fibers.
Thread forming (rolling) makes the strongest threads. These are 30-50% stronger than cut threads!
When to Use Each Type for Different Jobs
Use Tapped Holes For:
- Home projects
- Furniture
- Small electronics
- Toys
Use Other Threaded Holes For:
- Car engines
- Airplanes
- Medical tools
- Big machines
How Much They Cost
Tapped holes cost about $0.10-$2.00 each when you make just a few.
Thread-milled holes cost about $0.50-$5.00 each but are better for big jobs.
Questions People Ask a Lot
Can I make a threaded hole in a hole that’s already there?
Yes! You can use a tap to add threads to a hole that’s already drilled.
Why would I use thread milling instead of tapping?
Thread milling is best for hard metal, big holes, and when you need very good threads.
Which type of threaded hole is strongest?
Rolled threads (thread forming) are the strongest because they don’t cut the metal fibers.
How do I fix a hole with bad threads?
You can use a thread insert (like Helicoil®) or make the hole bigger and use a bigger screw.
Tips for Success
- Always use the right size drill before tapping
- Go slow when tapping by hand
- Use cutting oil to make the tap work better
- Back the tap out often to clear chips
- Check the threads with a screw before finishing
Tools That Help Make Better Threads
- Tap guides help keep the tap straight
- Thread gauges check if threads are right
- CNC routing can help make perfect holes
- Special coatings make taps last longer
Final Thoughts
Now you know the difference between tapped holes and threaded holes! Remember:
- Tapped holes are made with a tap tool
- Threaded holes can be made in many ways
- Pick the right one for your job based on what you’re making
- Both types help hold things together with screws
For big jobs with lots of threaded holes, think about using CNC machining services to get the job done right!
