I believe that by using the power of mathematics and our friend desinishon here, we should be able to figure out a rough estimate of how much damage the Digger machine does!
Now desinishon, you're going to have to be our mathematician, since you're the only one who knows all the details for this to work.
1) Start by looking at all the phase changes and adding up all the damage you've taken from the attacks. Add whatever possible damage you may have taken during the night to that as well. Then you can subtract that from your total health and you'll have your HP before the Digger attack.
2) Based on your reactions to being hit by the Digger, it seems to me you don't know your current HP, AFTER the Digger attack. Take your total health and multiply it by .2 (or just divide it by 5). This is the damage required for you to be in redbar, which is less than one-fifth of your total health. Based on the phase change post, I'd say that you'd hypothetically be in redbar. So by that logic your current HP should be somewhere between 1 and this number.
3) Now if you did the math right, you should be able to subtract your number you got in 2) from your answer in 1) and get a number somewhere around...hm, I'd put my guesstimation at around 50-70 (don't quote me on that, it's actually likely a higher number). This should be a rough estimate of how much HP the Digger does!
Cool, huh? I'll even write out a tl;dr formula for it since I'm so nice.
So, there ya go! If you would kindly post this number in the thread, we can all know how much damage the Digger does, too! :D