This is a design for an enclosure for the Half Size MachTach machine tachometer
http://www.machtach.com
The enclosure has top and bottom halves which fit together with a small lip. The sensor and power connectors are accessible from the side/back. The display and rotary encoder have openings on the top. There is a recess for the plastic lens material from inside the top half of the enclosure. The enclosure and MachTach module are all held together with four #4 x 1" sheet metal screws.

Update 1-29-2017: New version with better standoff support. The round pads are to hold the corners down during printing. They snap off after completion.