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Figure 4 - Marking the dimensions of the keypad for cutting
Figure 4 - Marking the dimensions of the keypad for cutting

When choosing a project case for the numerical keypad, consider the width of the main panel circuit board because it has to fit between the edges of the box lid or sides. If you have the SparkFun keypad, there is a very detailed drawing and printable template on their website. Since my hand cutting would be the weak link, I just decided to trace out the dimensions as shown in Figure 4 and then hand-bombed the rounded edges by drawing them freehand. Hand cutting the rounded rectangle will be okay using a notching tool and a small round file, so perfect accuracy won't be possible.



Figure 5 - The notching tool is a great addition to your hacking toolkit
Figure 5 - The notching tool is a great addition to your hacking toolkit

Whenever you are faced with the task of cutting a square or rectangular opening in a thin plastic or metal project box, the notching tool shown in Figure 5 will make the job easy. This tool basically nibbles a tiny square bit out of the surface each time you close the pliers, so you can notch away along a straight line, creating any size opening with straight edges. The tool is no replacement for a CNC mill, but it does a decent job for prototyping. You will have to drill starter holes at each corner and then work the notching tool along the edge until all four corners have been connected. A fine pitch flat file can be used to clean up the edge later if necessary.

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