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Surface roughness standards generally say that the thing you specify is the maximum your willing to accept. But manufacturer could make a finer job if they wished.

I however have a situation where the surface has to be quite rough and im having problems with my supplier naturally making better surface quality than I want.

So for now ive clarified this in text and that works fine for now. But just for clarity, how would i have actually supposed to document this in a standards compilant way in the drawing?*

* Not that i think it would have helped as im pretty sure the machine shop would not have understood it without clarification but just out of curiosity.

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    $\begingroup$ The ME group at a company I used to work at was in a similar situation to yours, trying to maintain a minimum amount of roughness in a camera part. For the next product, we just threw up our hands and made a 3D model with a whole bunch of tightly specified ridges that added up to the necessary roughness. I'm not sure how much it cost to get it machined, but manufacturing and incoming inspection were sure happy with it. $\endgroup$
    – TimWescott
    May 26, 2023 at 4:10

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I am not sure what the current recommendation in the international standards is, since in mechanics I realized that a lot of things vary from industries to industries, and in the same industry from companies to companies.

However, I have most of the time seen and used the recommendation below, taken from this Cheat Sheet on Drawing Indictation of Surface Texture.

Indication of a range of surface roughness (RA) on a technical drawing

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  • $\begingroup$ The good thing about standards is that theres so many to choose from. 🙂 $\endgroup$
    – joojaa
    May 25, 2023 at 14:49
  • $\begingroup$ I could not agree more haha! $\endgroup$
    – KrKAlex
    May 30, 2023 at 7:31

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