Dimensioning and Sizing of Keyways in Technical Drawings

A keyway on a stepped shaft(Image Source: Picryl)

The technical drawing is a common language between engineers and manufacturing technicians all around the world. Well-prepared technical drawings can be understood by other people who are dealing with the manufacturing of that part. So, obeying technical drawing standards is a very important thing to obtain the best quality engineering drawings. 

Mechanical elements have a close relationship with engineering drawings. This is because all the machines and machinery include standard machine elements. And these standard machine elements must be included in technical drawings. 

One of these machine elements is the keyways and we would like to give a summary of information about how to show keyways in technical drawings. 

Check: Best Book to Learn Technical Drawing!

How to Show Size Keyways in Engineering Drawings?

Keyways are the geometrical features on shafts to attach keys. Keys are attached between shafts and the gears to transmit power from gear to shaft or shaft to gear. So, these keyways are designed according to the standards inlined with the dimension of the shaft and the total power that is to be transmitted. 

(Image Source: FREDERICK E. GIESECKE, SHAWNA LOCKHART, Technical Drawing With Engineering Graphics 15th Ed., Pearson, Pg.525).

The standard dimensioning of the keyway is like above. From the right side of the shaft total diameter is given with tolerances. Ann from the top of the shaft, the keyway is shown. The gap of the keyway is shown with tolerances again and the semi-gap is shown. And the dimension is added from the bottom of the keyway to the bottom perimeter of the shaft to give information about the deepness of the keyway according to the shaft diameter. 

In general, keyways are designed according to standard keyway productions, and all the dimensions are given by the key manufacturers. Minimum required dimensions are calculated and minimum sized keyways are selected which ensures the required dimensions. 


Dimensioning and sizing the keyways in technical drawings are very simple like this. Learning these kinds of tricks will make you a better technician or engineer. 

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