Maximum Surface Roughness for Common Machined Part Features

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Maximum Surface Roughness for Common Machined Part Features

Typical Maximum Surface Roughness of Common Machined Part Features Table.

The following design data is the maximum functional roughness that might to specified for functional parts and features.

Surface or part	Maximum roughness
Surface or part	µm	µin
Chased threads	6.3	250
Clearance surfaces (machined)	6.3	250
Surfaces for soft gaskets	3.2	125
Housing fits (no gasket or seal)	3.2	125
Die- or tap-cut threads	3.2	125
Datum surfaces for tolerances over 0.025 mm (0.001 in)	3.2	125
Mating surfaces: brackets, pads, faces, bases, etc.	3.2	125
Teeth of ratchets and pawls	1.6	63
Gear teeth (ordinary service; diametral pitch over 10)	1.6	63
Datum surfaces for tolerances under 0.025 mm (0.001 in)	1.6	63
Milled threads	1.6	63
Pressed fits, general: keys and keyways	1.6	63
Rolling surfaces, general: cams and followers, etc.	1.6	63
Surfaces for copper gaskets	0.80	32
Slideways and gibs	0.80	32
Journal bearings, general	0.80	32
Push fits	0.80	32
Sliding surfaces of mating mechanisms or parts, general	0.80	32
Worm gears, general	0.80	32
Rotating surfaces, general: pivot pins and holes, etc.	0.80	32
Pistons	0.40	16
Cam lobs (automotive)	0.40	16
Cylinder bores: O-rings or leather packings	0.40	16
Ground screw threads and worms	0.40	16
Piston rods: O-rings or leather packings	0.40	16
Gear teeth (heavy loads)	0.40	16
Gear teeth (ordinary service; diametral pitch under 10)	0.40	16
Journal bearings (precision)	0.40	16
Sliding surfaces of mating mechanisms or parts (precision)	0.40	16
Worm gears (heavy loadings)	0.40	16
Valve stems (automotive)	0.40	16
Rotating surfaces (precision)	0.40	16
Friction surfaces: brake drums, clutch plates, etc.	0.40	16
Cylinder bores (automotive)	0.33	13
Seats for antifriction-bearing races	0.25	10
Crankpins	0.20	8
Valve seats	0.20	8
Rolled threads	0.20	8
Rolling surfaces (precision; heavy-duty)	0.20	8
Piston pins	0.13	5
Surfaces of fluid seals (sliding or rubbing)	0.13	5
Pressure-lubricated bearings	0.13	5