1-3/16" is simple. 1.1875 or thereabouts is a pain in the **** to mentally convert though. Inches are in fractions, not tenths. Thou are simple to convert as they readily convert to a fraction or millimetre and are only used in small amounts. Someone says five thou, it's easy. Someone reels off 3.380 at you though and you have an absolute **** of a time figuring out what that translates to. Use either imperial or metric; There's no inbetween.![]()
Decimal inch to mm is a simple matter of x 25.4. How that's harder than figuring 32nds I don't know. Decimal inch is the only sane way of adding up inch dimensions on a part too, or doing trig, or machining tolerances.
What about thousandths? By definition, they are part of the decimal inch 'system'.
Some people use the imperametric system when stating sizes. eg plywood 8×4x18mm![]()