Convert Inches into millimeters
A very simple trick, but also very usefull : a pocket calculator, intended to convert currencies, can be easilly tranformed to convert inches into millimeters and vice versa.
I take a standard pocket calculator, like this Casio HL-820VER I have purchased for less than 3 euros.
You need to change the conversion rate to 0,03937 and you obtain a calculator that translates inches into millimeteres and millimeters into inches.
On that model, to change the rate :
[C/AC] [C/AC] [%]Rate select (maintenu 3s) 0.03937 [%]Rate select
To display the rate :
[C/AC] [%]Rate select
To finish with, I have glued some little labels on the keys to avoid any confusion on the sens of the convertion. (glued and lacquered with CA glue).
To use it, very simple :
- Convert into millimeters : enter the value in inches, example :  [/]   [=] and you hit [–>mm] and you obtain : 1/64th of an inch = 0.4 mm
- Convert into Inches : enter the value in millimeters, axample   [.]  and you hit [–>Inch] and you obtain : 25.4 mm = 1 inch.