Insurance, please help us, our extremely valuable wood tools were incinerated in a fire!

i'm not sure what you're working on, but you'd want an intermediate spool with a single winding around a known diameter, the spool would be on an axle with say a larger diameter disk with evenly spaced marks around its outside edge, and an optoelectronic sensor counting each mark that passes. set the number of marks to count, corresponding to the length of thread you want to wind.