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Question in short

The following drawing is a ball-screw with both ends mechanized and a ball-nut on it.

What is the meaning of the indicated notations?

enter image description here

Context

What is clear to me are:

  • Indications of sizes/distances
  • Angles
  • Parameters of precision/error
  • Diameters

It seem that the little letter (e.g. 2) are related with the values in the box, but I can't understand the meaning. The 1 is completely obscure to me.

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  • $\begingroup$ This is a very broad question. I suggest that you research GD&T and metrology to understand those symbols. We could spend hours/days teaching the concepts $\endgroup$ – GisMofx Dec 1 '17 at 21:12
  • $\begingroup$ Actually, when one know what to search and has a starting point (thanks to your answer), it does not seem that difficult. $\endgroup$ – Adrian Maire Dec 1 '17 at 21:25
  • $\begingroup$ You're welcome. It's fairly straight forward once you understand the basic concepts. If you have a detailed follow up question, I'll be happy to try to answer it. $\endgroup$ – GisMofx Dec 1 '17 at 21:36
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What you are asking is mainly in reference to the GD&T feature control frames on the drawings. Your drawing looks like it's metric, so it may refer to an ISO standard.

If your drawing references a specification, you should research that as this answer would essentially need to teach you GD&T and how to interpret it. Maybe start here: https://en.m.wikipedia.org/wiki/Geometric_dimensioning_and_tolerancing

But there are several resources online.

That being said:

  1. Machined Surface Finish requirement(material removal required) as indicated by the integrated horizontal line below the value.
  2. It looks like a datum callout
  3. Concentricity or Coaxiality(depending on spec and interpretation)(not commonly specified)
  4. Circular Runout(typically used over concentricity)
  5. Perpendicularity

What GD&T does is to clearly define what features are important and how they are to be inspected. They are used to control position and/or form of the part. In your case, that's a rotating shaft so typically the cylinders need to be concentric so they are balanced and aligned for assembly.

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  1. This is an indication of surface finish.
  2. This is an indication of a datum
  3. This is an indication of concentricity
  4. This is an indication of runout
  5. This is an indication of perpendicularness

Almost all of these relate to GD&T, which I would recommend you read up on. The fact that you don't know these shows a general lack of knowledge. I would recommend skimming something like ASME y-14.5, or taking a class on drafting.

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