CNC Threaded Holes: Tapped Holes vs Threaded Inserts vs Through Holes

Threads are small.

The headache they can create is not.

When designing a CNC aluminum part, there are several ways to make a threaded connection.

Directly Tapped Hole

This is the simplest option.

The thread is machined directly into the aluminum.

It works well when:

• the material is suitable
• the thread depth is sufficient
• the assembly load is reasonable
• the connection does not require frequent service

For many CNC aluminum brackets and housings, direct tapping is perfectly practical.

Threaded Insert

An insert adds a separate threaded component inside the machined hole.

This can make sense when the design needs:

• repeated assembly and removal
• improved thread wear resistance
• stronger thread engagement in certain applications
• compatibility with a specific fastening system

But an insert also adds another manufacturing and assembly step.

So don't specify one just because it sounds more “industrial."

Through Hole + Nut or Fastener

Sometimes the simplest answer is no internal thread at all.

A through hole with a bolt and nut can be easier to manufacture and service, depending on the assembly.

Which One Should You Choose?

Start with the actual job of the connection.

Ask:

Is the screw installed once?

Will it be removed 100 times?

Is the part aluminum?

Is space limited?

Is the joint highly loaded?

Is serviceability important?

There is no universal winner.

The right choice depends on the assembly.

And here's the shop-floor rule:

Don't design the fastener first. Design the connection first.

One More Detail

If a machined aluminum part will be anodized, identify critical threads and mating areas clearly.

Coating can affect dimensions, especially where close fits are involved.

Have threaded features in your part? Send the drawing so the thread specification and critical dimensions are clear before machining.

Please click the contact link on the right and send the drawings to me.