Dimensioning Curves and Curved Surfaces in Engineering Drawings

Dimensioning Curves and Curved Surfaces in Engineering Drawings

Technical drawing is a very important tool for communication between engineers and technicians all around the world. In technical drawings, various kinds of standards are used. If you obey these standards when you create or draw your technical drawings, others will easily understand what you want to tell people all about the technicalities of your project or part. 

In some cases, showing all the features in technical drawings can be troublesome. For example, you can show and dimension nearly all the geometrical shapes without any difficulty. But if you need to dimension and size curves, it can be burdensome for the reader and creator. Maybe curved lines are not used because of this reason in mechanical designs…

How to Dimension and Show Curves in Technical Drawings? 

There are different methods to show curves in technical drawings. 

If the curve to be dimensioned includes a set of curves, you can show that show with a set of radii dimension leaders. As you see below, a curve contains different kinds of radii which are joined end to end to obtain a complete curve. To show that curve in a detailed way in technical drawing, all the radii of the sub-curves are shown with radius dimensions separately. 

Image Source: Image Source: FREDERICK E. GIESECKE, SHAWNA LOCKHART, Technical Drawing With Engineering Graphics 15th Ed., Pearson, Pg.522

A shape in a technical drawing may contain both straight lines and curves like below. In this case, it is much easier to show all the dimensions in a detailed way. You just need to show all the primary dimensions according to the dimensioning and sizing rules and show all the radii according to the rules. 

What if Curves Does Not Contain Sets of Radii?

Image Source: Image Source: FREDERICK E. GIESECKE, SHAWNA LOCKHART, Technical Drawing With Engineering Graphics 15th Ed., Pearson, Pg.522

Sometimes, there can be curves that can not be dimensioned with linear dimensions or radius dimensions. In this case, the coordinate system dimensioning technique can be applied. As you see in the example below, datums are used and these datums are dimensioned according to the absolute point of the curve. This method can give a very strong idea about this curve to the reader of that technical drawing. 

Conclusion

These techniques to dimension irregular curves can help you in hard situations like above in technical drawings. You need to learn these kinds of tricks to master both reading and creating engineering drawings.

Do not forget to leave your comments and questions below about dimensioning curves and surfaces in engineering drawings! 

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