3x 5mm pin hole in 50mm spacing. 

Requires center drill and try-square.

Center drill outer diameter 8mm - drill bit 5mm.

Try-square's plate dimensions 24.8x2mm

For assembly 6xM3 nuts and bolts + 2xM3 nut and bolt for plate fixing
 

Printed with anycubic mega: layer height 0.2, nozzle 0.4, PLA. 
Supports needed under hex nut holes.