So I made a mini tree for quench-temper combinations. At the moment tempering is broken, but when it is fixed, we can mathematically calculate the best possible combination to get to a certain part of the tree. PS, yes in the handbooks says you can only go linear quench-temper-quench etc, but either they lied, it's bugged (thus I wasted my time), or they changed it in a pre release. Either way, this tree mechanic is WAY more fun than the boring linear thing.
I've done some testing across the tree and I've got into the ballpark of what the shatter-chance and power-gain curves look like. Shatter chance is linear (gradient is 5), but for power-gain I highly suspect it isn't a single function, but multiple, and, using regression, I was only able to plot it semi-accurately to a quartic function. Different curves for different routes through the quench-temper tree.
As for tempering, it looks like an exponential curve, though I couldn't match it completely. Green function is the power gain; red is the shatter chance. At the moment tempering is useless, broken, and harmful I made a post on it on discord, hope the devs see it.
I put everything into tables. Here's some common obtainability chances after quenching a toolhead a certain number of times. Notice at 18 quenches in the far right table, the shatter chance and power gain drop, almost like a tempering mechanic. Not sure if this is intended but it fits into the quartic curve well. At 0.004% obtainability though, no one will ever have to worry about that (you've have to go through 250,000 tool heads)
Plotting it on a graph shows us how unobtainable certain quench numbers are. We can use this to calculate how many toolheads we'd need to get to a certain obtainability. For example, if I want to do 6 quenches (and get 40% power gain), it is ~55% obtainability, meaning I'd need 1/.55 ~= 2 toolheads. We can also do this backwards. If I have 10 toolheads to sacrifice, how many quenches would I be able to get probabilistically? 1/10 means I'd need at least 10% cumulative shatter chance, and we can see about 11% gives us 10 quenches. 9 tools shatter, 1 remains, giving us ~58% power gain.
And finally, the chart for how many toolheads you'd need for different number of quenches (Q#, no tempering).
Please devs show me the functions you used for shatter chance, power gain etc. I spent too long on this
If I'm able to get the exact functions, I will use it to write a python code that gives you the best possible path to get to a certain part of the tree.
Some changes I would make to the system
-Return metal from shattered toolheads
-Allow removal of toolhead from tool to allow re-quenching. This would make the whole system more dynamic.