I could have a guy 3-d print one, but anyone already have a setup?
At Brownell's, they are like $50 for a tube with a bolt and an electronic scale.
This is simply to satisfy a curiosity, not because I am tuning the world's best 1911 build.
This is for a 1911 recoil spring, FWIW.
Fishing scale-
Make a plunger that will pass through the axis of the spring- drill a hole in a board that the plunger will go through, hook the scale to the plunger and pull.
The plunger could be as simple as a piece of bent welding rod- think screen door extension spring.
Springs are typically measured per inch
16-24 lbs?
You can also use a trigger pull weight gauge. Unload the gun and rack the slide to cock the Hammer. Pull the slide back enough to Hook the trigger pull gauge on the top of the breach face where the top of the barrel hood engages the breach face. Then pull the slide back with the Trigger Pull weight gauge just before the bottom of the slide touches the cocked hammer. This will give you a fairly close reading of what the recoil spring weight is. If you pull the slide back too far where the bottom of the slide over cocks the hammer that will add additional weight to the measurement.
Realistically though, if you don't know what the Recoil Spring weight is, simply buy a new recoil spring of whatever weight you want. Springs are cheap.