Surface Finish Degree Comparison Table between Rz Ra RMS

The following comparison table was edited by SST. You can find the comparison for the new standard in China for the Ra and Rz, and the micron, microinch Ra in USA. In addtion, we also lised the old grades in China for your reference. The old grades are still widely used in China. We usually called the Downward-pointing Triangle as "hwar". The comparison table just for your reference, should not be taken as the inspection standard.

China Old Grade	China New Ra	China New Rz	USA micron Ra	USA microinch Ra
▽ 1	50	200
▽ 2	25	100
▽ 3	12.5	50
▽ 4	6.3	25	8.00	320
▽ 4	6.3	25	6.30	250
▽ 5	3.2	12.5	5.00	200
			4.00	160
			3.20	125
▽ 6	1.6	6.3	2.50	100
			2.00	80
			1.60	63
▽ 7	0.8	6.3	1.25	50
			1.00	40
			0.80	32
▽ 8	0.4	3.2	0.63	25
			0.50	20
			0.40	16
▽ 9	0.2	1.6	0.20	12.5
				10
				8
▽ 10	0.1	0.8	0.10

RMS (microinch)	RMS (µm)	RA (microinch)	RA (µm)	Grit Size
80 58 47 34 17 14	2.03 1.47 1.2 0.6 0.43 0.36	71 52 42 30 15 12	1.90 1.32 1.06 0.76 0.38 0.30	80 120 150 180 240 320

Releated References:
1. ISO 1302 DIN 4768 Comparison of Surface Roughness Values
2. Electrical Discharge Machining EDM Roughness Comparator
3. Polishing Polished Seamless Stainless Steel Pipe Tube
4. Stainless Steel Tubes Surface Roughness Review
5. Stainless Steel Bright Annealing/Annealed Tubes
6. China USA Surface Roughness Standard Comparison
7. Surface Roughness Conversion Chart of Stainless Steel Tube
8. Stainless Steel Tube Surface Finish Types
9. Cleaning of Stainless Steel Tubes
10. Post weld cleaning and finishing of stainless steels
11. Care and maintenance of stainless steel
12. British and American standards for tolerances, surface finish and testing of stainless steel
13. Surface Finish Degree Comparison Table between Rz Ra RMS