Conversion of Ra to Rz surface roughness

[Madhu454]

Hi,
Is there any thumb rule or acceptable guidelines to convert Ra surface roughness values to Rz surface roughness values?

 

[dgallup]

There is no formal or accurate conversion as they are measuring two different characteristics. However, as a rule of thumb, I've seen factors of 8 to 10 used (multiply Ra by 8 or 10 to get Rz).

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[EdStainless]

You need to get the standard out and read the definitions. I have seen the ratio between them as low as 5 and as high as 20. They are two very different characteristics.

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P.E. Metallurgy, Plymouth Tube

 

[RolMec]

Hello,

what I propose (& do it myself all the time) is to look at this from the manufacturing, i.e. specific machine and machining p.o.v.
In the / some appropriate handbook there shall / should be tables alike this one:

which makes it possible to converse roughness values, at least for standard purposes (~ I'm located in heavy to medium mechanical manufacturing).
Additional hint: for every machining process the usual equipment is characterized by a certain achievable surface quality range. The range itself is defined by e.g. speed of machining, quality of tools,..
Ultimately, your request is a good incentive to talk to (your) workshop people ;-)
Regards

Roland Heilmann
Lpz FRG

 

[Madhu454]

Hi All,
Thanks for the reply. It was helpful.