Not everything precise.
Only what is functionally critical.

Typical critical areas

These surfaces and features often require targeted post-processing:

Bores

Reaming or drilling to size

As-sintered tolerance is usually not sufficient for a fit

Threads

Cutting after sintering

Tapping into the sintered part is a common step

Sealing surfaces

Define flatness and roughness

As-sintered surface roughness is often too high for sealing seats

Mating surfaces

Tolerance position per DIN/ISO

Mill or grind locally to nominal size

Datum surfaces

Location, alignment, assembly

Defined contact surfaces for installation position

Function-critical contours

Local, part-specific

What the function requires – not what the standard dictates

Where the blank is often sufficient

Not every surface has to be machined. Large portions of a well-designed A-MIM blank can remain in the as-sintered state:

• Geometrically non-critical outer regions – shape is right, tolerance is irrelevant
• Non-functional secondary surfaces – visible surfaces without contact or sealing function
• Integrated complexity – internal channels, cavities, ribs that need no fit
• Large-area contours – when dimensional accuracy within sintering capability is sufficient

When post-processing makes sense

1

Function needs precision locally

When a surface needs a defined tolerance that sintering does not deliver.

2

Leak tightness required

Sealing seats for rings, flanges or screw connections – post-process roughness and flatness.

3

Fit or datum required

Bores, bearing seats, guides – bring to size when the part has to be installed.

4

Surface functionally relevant

Friction, wear, visual requirements – polish, grind or blast locally.

Basic economic logic

The blank carries the shape → what the function requires is machined → the ready-to-install part is what gets compared.

The fewer surfaces have to be machined, the greater the advantage usually is. A blank machined more extensively can also make sense – for example when it clearly saves material removal or setups compared with machining from solid stock. What matters is the entire manufacturing chain.

Recommendation: provide machining allowances only on the surfaces that need them, and define the scope early – this makes the comparison with other processes reliable.

What this can look like in practice – application concepts with starting situation, possible advantage and remaining machining.