Surface Finish

Surface Finish Applications

Ra Surface Rating [µm]	Application
25	Rough, low grade surfaces resulting from sand casting, saw cutting or rough forging. Rarely specified, but suitable for rough clearances in construction.
12.5	Rough, low grade surface for clearance areas in machinery, jigs, and fixtures. Natural surface for sand castings or rough forging.
6.3	Coarse production surface for unimportant clearances and clean up operations. Natural surface of forgings, extrusions, and permanent mouldings.
3.2	Roughest surface recommended for parts under load, vibration, or high stress.
1.6	Used for close fits, stressed parts, and bearing interfaces.
0.8	Suitable for stress concentration surfaces and bearing surfaces under light loads.
0.4	High quality surface for rapidly rotating shaft bearings, heavily loaded baring surfaces or extreme tension members.
0.2	A fine surface used in precision gauges, instrument work, or rapidly rotating surfaces where lubrication is not desirable.
0.1	A costly refined surface for instruments, gauges, and sliding surfaces where lubrication is not dependable.
0.05	A polished appearance for sensitive instruments, laboratory items and precision gauge blocks.
0.0025

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Process Capability

Process	25	12.5	6.3	3.2	1.6	0.8	0.4	0.2	0.1	0.05	0.025	0.012
Superfinishing								•	•	•	•
Lapping							•	•	•	•
Honing						•	•	•	•
Cylindrical grinding					•	•	•	•	•
Diamond turning					•	•	•	•	•
Plane grinding					•	•	•	•	•
Boring, Turning			•	•	•	•	•
Extruding				•	•	•
Broaching				•	•	•
Reaming				•	•	•
Cold Rolling, Drawing				•	•	•
Die Casting				•	•	•
Milling			•	•	•	•
Drilling			•	•	•
Planing, Shaping		•	•	•	•
Sawing	•	•	•	•	•
Forging		•	•	•
Sand Casting		•	•	•
Hot rolling	•	•

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