Thanks @James46717 and @Jeff105671 
Accounting for additional variables
Seems like there are a lot of variables. But that’s ok, I’d be happy with a value +/- 30% of my calculations.
I.e. if I calculate 30c above room temperature an “in practice” 21-39c would be absolutely fine. None of the temps in that range is so hot it will burn you or be unsafe.
Getting in the ball park
Oh that’s what the C/W stands for! Thanks.
Let’s just test I understand this table with an example.’
So for this TO-220 we are expecting 5 degrees per watt.
W = A*(Vo - Vi)
W = 0.1 * 13 => 1.3W
so that’s an additional 6.5c above room temperature.
Maybe as my project evolves I start to draw .4 amps.
That’s 26 degrees which will be warm but still… ya know… safe.
How did I do?
EDIT : This turned out to be wrong, I needed to read the bottom row of the C/W table.
It’s 50degrees per watt…
