Custom CNC Turning and Turn-Mill Machining for Aerospace Components

This 316 stainless steel aerospace component is small—approximately 28 × 10 mm—but it combines several types of machining in a very limited space.

The main body is rotational. The cylindrical surfaces, internal bore, stepped diameters and circular shoulders are natural CNC turning features. The part also includes openings, slots and side details that move away from the turning axis and require milling.

That combination made CNC turn-mill machining a practical choice for this project.

Most dimensions are controlled around ±0.05 mm, while selected critical features are specified down to ±0.01 mm according to the customer drawing.

The finished parts are supplied to a customer in the United States for an aerospace application.

Project Specifications

The Part Naturally Starts on a CNC Lathe

Looking at the round geometry first makes the machining route easier to understand.

The OD, bore, stepped diameters and shoulders can all be established through CNC lathe machining. These features form the basic body and provide references for the details that come afterward.

If the component ended there, conventional CNC turning would be enough.

But several features interrupt the rotational geometry. They cannot be produced simply by moving a turning tool along the part's axis.

Those details need milling.

The important point is that the milled features still belong to the geometry established during turning. A slot or side feature may be small, but its position can relate directly to a turned bore, shoulder or outside diameter.

That is where the job moves from straightforward turning into turn-mill machining.

Keeping the Turning and Milling Connected

One possible route would be to complete the turned body first, remove the component and fixture it again on a separate milling machine.

Sometimes that is exactly what we do.

For this part, however, keeping more of the operations within a coordinated CNC turning and milling process makes sense. It reduces additional handling and gives us a more direct way to work from the turned geometry when machining the off-axis details.

This becomes particularly useful on a component only about 28 × 10 mm.

Small parts do not offer much room for unnecessary workholding, and every new setup introduces another reference that has to be established correctly.

The advantage of turn-mill machining here is therefore quite practical: keep related features related during machining.

±0.01 mm Where the Drawing Actually Requires It

Selected critical dimensions are specified down to ±0.01 mm, while other dimensions are around ±0.05 mm.

We think it is important to keep that distinction.

This is not a component where every dimension needs ±0.01 mm control, and describing it that way would exaggerate the actual machining requirement.

Instead, the tighter tolerances receive additional attention where the drawing calls for them.

Those dimensions may affect how the component locates, fits or works with surrounding parts in the customer's assembly. Other features are produced to their own specified tolerances.

For precision aerospace CNC machining, understanding where tighter control actually matters is more useful than simply trying to machine every dimension as tightly as possible.

28 × 10 mm Is Small, but the Geometry Isn't Simple

There is quite a lot packed into this component.

Within a maximum size of approximately 28 × 10 mm, the part combines external turned surfaces, internal geometry, diameter changes, shoulders and several local features that require milling.

That affects tool access and machining sequence.

The turning operations need to establish the basic geometry without making the later milling unnecessarily difficult. The milled details, in turn, need to follow the references already created on the turned body.

This is why overall size can be misleading when evaluating a machining project.

A larger shaft with a simple profile may require relatively little machining. A much smaller component like this can involve several operations within a very limited working area.

Machining the Part in 316 Stainless Steel

The customer specified 316 stainless steel for this aerospace component.

For a small feature-dense part, the material needs to be considered together with the machining sequence. Tool access, cutting conditions and the amount of material removed in each operation all influence how smoothly the part moves from turning into milling.

There is no advantage in adding extra passes simply because the equipment allows them.

The circular geometry is turned. The off-axis details are milled. The machining route stays focused on what the drawing actually requires.

That sounds simple, but keeping the process simple is often useful when a component already contains a lot of geometry in a small space.

Custom CNC Turning for Parts That Need More Than Turning

Our custom CNC turning services cover many components that can be completed almost entirely on a lathe—shafts, pins, sleeves, bushings, spacers and other rotational parts.

Other drawings begin the same way but include additional flats, cross holes, slots or openings.

That is where custom CNC lathe machining can extend naturally into turn-mill work.

For this type of made-to-drawing component, we review the complete geometry before deciding whether the part should stay on a conventional lathe, move through separate turning and milling operations, or be produced using a turn-mill process.

Customers may also search for this capability as a custom CNC lathing service, although CNC turning and CNC lathe machining are the more common industry terms.

The terminology matters less than the drawing. The geometry tells us which process makes sense.

A Small Part Where the References Matter

What stands out about this component is not simply the ±0.01 mm tolerance or the fact that it is used in aerospace equipment.

It is the relationship between the features.

The bore, OD and stepped circular surfaces establish the turned body. The slots, openings and side details then need to follow that geometry in the locations defined by the drawing.

That is the reason turn-mill machining fits this project.

For a similar custom part, we would look at the same questions first: which features should be established during turning, which ones need milling, and which relationships are better kept within the same setup?

Once those are clear, the machining route usually becomes much easier to decide.