Hello, elie.maricau,
Personally is one of the details I like the most about JMP, the adaptive zooming axis.
In my experience you can fix the units, but not the "adaptive zoom". In a Column [Numeric, continuous], if you just do:
9416_Screen Shot 2015-08-05 at 1.14.02 PM.png
And then select an increment for "Y" like:
9417_Screen Shot 2015-08-05 at 1.14.36 PM.png
As soon as you move the axis the "Increment" adapts:
9418_Screen Shot 2015-08-05 at 1.19.28 PM.png
It will show the same units, but t will adapt.
What I have done way to keep units fixed, is changing the Column type to "Numeric, Nominal". Then change the Format to something simple, like hours.
9419_Screen Shot 2015-08-05 at 1.25.11 PM.png
This has worked for me. It keeps the ticks fixed.
9420_Screen Shot 2015-08-05 at 1.27.06 PM.png
9421_Screen Shot 2015-08-05 at 1.27.33 PM.png
Hope it helps.
-Jose