![]() Each roughness class from N1 to N12 has a maximum permissible Ra value according to DIN ISO 1302. The rule of thumb that repeatedly emerges for converting Rz = Ra*7 does not go far enough, and based on the extensive scattering of values, can lead to bad surprises in practice.Īdditionally, the surface quality is frequently subdivided into 12 roughness classes or roughness grades. ISO 4287-1:1997 7 defines Rz as the maximum height of profile. However, a conversion interval that contains all possible values can be specified. Het principe van het meten van gemiddelde ruwheid (Ra) 3. The surface roughness established by the calculation is thereby less vulnerable to extreme values than the roughness depth.Ī conversion of Rz to Ra and the reverse is not possible as 1:1 scale. In practice, the more realistic value Rz is also specified, which is determined by averaging 5 separately measured Rt values. 4288) are applied in an analogous manner, in that the surface finish quality is specified in Ra values or in the even more accurate Rt values. The arithmetic average roughness value Ra describes the arithmetic average of all deviations in the roughness profile from the median line within the measuring length. The international surface finish standards (DIN 4762, 4768, ISO 4287/1-2. The range of the two extreme values in the roughness profile, for the respective individual sections, is subsequently divided by the number of measuring sections. Ra ( ) Rz Ry ( ) Ra ( in)( ) Ra ( in)( ) Ra ( ) Rz ( ) ITALY a Y'R) Ra ( ) Ra ( ) UNI 13963-60 Ra ( ) Rz ( ) Ra ( ) Rz ( ) GB 1031-83 'HISO 468-83 BS 1134-61ASAB 46.1-62 CHINA N-V UK V USA V GERMANY V SWITZERLAND tX POLAND lQp CZECH cwQK JAPAN eg, DIN4763-60VSM 10321-62 PN 58/M 042-51CSNo 14450. To determine the averaged roughness depth Rz, a measuring segment is first established, and in turn, this is divided into (usually five) individual measuring lengths of equal size. ![]()
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