Engineering

Scaling In Technical Drawing And Some Standards

In technical drawing, scaling is a very important thing. When you are drawing technical drawings, showing very big parts or components in a small paper is done with the scaling. So, you need to specify the scale in a good way. Here you can find out general information about the scaling in technical drawing. 

Scaling In Technical Drawing

Consider that you are drawing a very big machinery part such as the crankshaft of a ship engine. The size of this part is very large to draw it in standard-sized technical drawing sheets. So, you need to scale this part while you are drawing on this sheet. 

For example, one geometrical length of that large part is 10 meters. You could not draw it in your sheet or you can not find a very large sheet to show this length directly. But, if you use a scaling proportion, such as 1:100, you can show this length in the technical drawing sheet as 10 centimeters. If you scale all the lengths and geometrical features with this rate, you can fit the part inside a small and standard technical drawing sheet. 

Crankshaft of a container ship(Image Source: www.reddit.com/r/Justrolledintotheshop/comments/3t1f5u/the_crankshaft_of_a_container_ship/).

If you use a scale rate while you are drawing technical drawings, you need to write this rate to the sheet, that a reader must understand the real size of that part. 

In a scaled technical drawing, lengths must be shown exactly. For the example above, you need to show the length as 10 cm or 100 mm, and you need to show the scale on the paper.

A 1:5 scaled assembly drawing(Image Source://www.designingbuildings.co.uk/wiki/Assembly_drawing).

Scales are generally shown in a special box on letterhead. 

Also, scales are used for showing the parts bigger in technical drawings. If a part is very small to show in a technical drawing, scales are used to enlarge that part on paper such as 2:1, 10:1, etc. 

General Scaling Standards In Technical Drawing

It is not a common practice to use random scales in technical drawing. Some scales are adopted in general technical drawings. These are 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200. 

Because of these standards, some special rulers are designed to measure the real lengths of the part which is drawn in one of these special scales such as 1:50. The length indicators on these rulers are written in real lengths. For example, the 10 cm length is shown as 10 meters for a special ruler which is prepared for a 1:50 scale. The reader can easily see the real dimensions from scaled technical drawings. 

A scaled ruler(Image Source: FREDERICK E. GIESECKE, SHAWNA LOCKHART, Technical Drawing With Engineering Graphics 15th Ed., Pearson, Pg.38).

Conclusion

This is the general information about the scaling in technical drawings.

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