Surface Roughness Conversion Chart Tables

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Surface Roughness Review

The following charts and tables convert surface finish or roughness between selected industry standard units.

Where:

Ra = Roughness, average in micro-meters & micro-inches
RMS = Root Mean Square in micro-inches
CLA = Center Line average in micro-inches
Rt = Roughness, total in microns
N = New ISO (Grade) Scale numbers
Cut-Off Length = Length required for sample.

Conversion math at bottom --

μ=0.000001m=0.001mm

μin=0.000001 in=0.0254 μ

Surface Roughness Conversion Chart
Ra micro-meters	Ra micro-inches	RMS	CLA (N)	Rt	N	Cut-Off Length
						in.	mm
0.025	1	1.1	1	0.3	1	0.003	0.08
0.05	2	2.2	2	0.5	2	0.01	0.25
0.1	4	4.4	4	0.8	3	0.01	0.25
0.2	8	8.8	8	1.2	4	0.01	0.25
0.4	16	17.6	16	2.0	5	0.01	0.25
0.8	32	35.6	32	4.0	6	0.03	0.8
1.6	63	69.3	63	8.0	7	0.03	0.8
3.2	125	137.5	125	13	8	0.1	2.5
6.3	250	275	250	25	9	0.1	2.5
12.5	500	550	500	50	10	0.1	2.5
25.0	1000	1100	1000	100	11	0.3	8.0
50.0	2000	2200	2000	200	12	0.3	8.0

Conversions (math):

CLA (micro inches) = Multiply Ra(µm) x 40
R_t = R a x 8.7
R_z = R a x 7.2
R_z ISO = R a x 7.6
R_max = R a x 8.0
R_p = R a x 3.6
RPM = R a x 2.9
RMS = R a x 1.1

Example:

Ra to Rt:
1.0 micrometer Ra x 8.7 (Rt Factor) = 8.7 micrometer Rt
40 microinch Ra x 8.7 (Rt Factor) = 348 microinch Rt

CHINA GB 1031-83 ≈ISO 468-83			UK BS 1134-61		USA ASAB 46.1-62		GERMANY DIN4763-60
Ra (μ)	Rz Ry (μ)	Code	Ra (μ in)(μ)	Code	Ra (μ in)(μ)	Code	Ra (μ)	Rz (μ)
0.008	0.032		1(0.025)		1(0.025)		0.01	0.04
0.01	0.04
0.012	0.05						0.016	0.063
0.016	0.063
0.02	0.08						0.025	0.10
0.025	0.10
0.032	0.125		2(0.05)		2(0.05)		0.04	0.16
0.04	0.16
0.05	0.20						0.063	0.25
0.063	0.25		4(0.10)		3(0.08)
0.08	0.32						0.10	0.40
0.10	0.40				4(0.10)
0.125	0.50		8(0.2)		5(0.125)		0.16	0.63
0.16	0.63				6(0.16)
0.20	0.80				8(0.2)		0.25	1
0.25	1		16(0.4)		10(0.25)
0.32	1.25				13(0.32)		0.40	1.60
0.40	1.6				16(0.4)
0.50	2		32(0.8)		20(0.5)		0.63	2.5
0.63	2.5				25(0.63)
0.8	3.2				32(0.8)		1	4
1	4		63(1.6)		40(1)
1.25	5				50(1.25)		1.6	6.3
1.6	6.3				63(1.6)
2	8		125(3.2)		80(2)		2.5	10
2.5	10				100(2.5)
3.2	12.5				125(3.2)		4	16
4	16		250(6.3)		160(4)
5	20				200(5)		6.3	25
6.3	25				250(6.3)
8	32		500(12.5)		500(12.5)		10	40
10	40
12.5	50						16	63
16	63		1000(25)		800(20)
20	80						25	100
25	100				1000(25)
32	125						40	160
40	160
125	200						63	250	S
63	250
80	320						100	400
250	400
							160	630
							250	1000
								1600
								2500

 

CHINA GB 1031-83 ≈ISO 468-3			SWITZERLAND VSM 10321-62			ITALY UNI 13963-60		POLAND PN 58/M 042-51
Ra (μ)	Rz Ry (μ)	Code	Ra (μ)	Code		Ra (μ)		Ra (μ)	Rz (μ)	Code
0.008	0.032		0.025	N1		0.025		0.01	0.05
0.01	0.04
0.012	0.05							0.02	0.10
0.016	0.063
0.02	0.08
0.025	0.10							0.04	0.20
0.032	0.125		0.05	N2		0.05
0.04	0.16
0.05	0.20							0.08	0.40
0.063	0.25		0.1	N3		0.08
0.08	0.32
0.10	0.40					0.1		0.16	0.80
0.125	0.50		0.2	N4		0.12
0.16	0.63					0.16
0.20	0.80					0.2		0.32	1.60
0.25	1		0.4	N5		0.25
0.32	1.25					0.3
0.40	1.6					0.4		0.63	3.20
0.50	2		0.5	N6		0.5
0.63	2.5		1.6	N7		0.6
0.8	3.2					0.8		1.25	6.30
1	4					1
1.25	5					1.2
1.6	6.3					1.6		2.5	10
2	8		3.2	N8		2
2.5	10					2.5
3.2	12.5					3		5	20
4	16		6.3	N9		4
5	20					5
6.3	25					6		10	40
8	32		12.5	N10		8
10	40					10
12.5	50					12		20	80
16	63		25	N11		25
20	80
25	100							40	160
32	125		50	N12
40	160
125	200							80	320
63	250
80	320
250	400

 

CHINA GB 1031-83 ≈ISO 468-83			JAPAN JIS B0601-70
Ra (μ)	Rz Ry (μ)	Code	Ra (μ)	Rz (μ)	Rmax (μ)	Code
0.008	0.032		(0.0125a)		(0.05S)
0.01	0.04
0.012	0.05
0.016	0.063		0.05a	0.1Z	0.1S
0.02	0.08
0.025	0.10
0.032	0.125			0.2Z	0.2S
0.04	0.16
0.05	0.20
0.063	0.25		0.1a	0.4Z	0.4S
0.08	0.32
0.10	0.40
0.125	0.50		0.2a	0.8Z	0.8S
0.16	0.63
0.20	0.80
0.25	1		0.4a	1.6Z	1.6S
0.32	1.25
0.40	1.6
0.50	2		0.8a	3.2Z	3.2S
0.63	2.5
0.8	3.2
1	4		1.6a	6.3Z	6.3S
1.25	5
1.6	6.3
2	8		3.2a	12.5Z	12.5S
2.5	10
3.2	12.5
4	16		6.3a	(18Z)	(18S)
5	20			25Z	25S
6.3	25
8	32		12.5a	35Z	35S
10	40			50Z	50S
12.5	50
16	63		25a	(70Z)	(70S)
20	80
25	100			100Z	100S
32	125		(50a)	140Z	140S	S
40	160			200Z	200S
125	200
63	250		(100a)	280Z	280S
80	320			400Z	400S
250	400
				560Z	560S

 

Parameter	Factor
Rt	8.7
Rz	7.2
Rz ISO	7.6
Rmax	8.0
Rp	3.6
RPM	2.9
RMS	1.1

Surface Roughness Value Equivalents

The Waviness is the measure of surface irregularities with a spacing greater than that of surface roughness. These usually occur due to warping , vibrations , or deflection during machining.

• ASME B46.1
• ASME Y14.36M - 1996 Surface Texture Symbols
• ISO 468:1982 “Surface roughness — parameters. Their values and general rules for specifying requirements.”
• ISO 4287:1997 “Surface texture: Profile method — Terms, definitions and surface texture parameters.”
• ISO 4288:1996 “Surface texture: Profile method — Rules and procedures for the assessment of surface texture.” Includes specifications for precision reference specimens, and roughness comparison specimens, and establishes requirements for stylus-type instruments.”
• ISO 8785:1998 “Surface imperfections — Terms, definitions and parameters.”
• ISO 10135-1:CD “Representation of parts produced by shaping processes — Part 1: Molded parts.”

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