Squier Jazzmaster middle screw, what for ?

[soulkitchen]

I have Squier Deluxe Jazzmaster and wonder what that screw for ? when I turn the screw I don’t see anything moving, but me an my tuner hear that strings tuning is changing. What is this screw for and and where should be tightened?

[MayTheFuzzBeWithYou]

It should set the tightness of the spring - so also how the vibrato „feels“ when you push the arm down.
And with that it also changes the distance of the angle/height of the vibrato-arm.
So there should definitely be something moving.
Maybe set your arm parallel to the strings and check the distance of the tip before and after.

Here is a good read:
Demystifying the Fender Jazzmaster and Jaguar but your unit is a simpler one that doesn‘t have the „lock“ (so also less to worry about).

[timtam]

This link is generally regarded as the gospel on setting up the trem spring compression via that screw, on a trem with a lock button (not sure that there were any trems without a lock button when it was first written).
https://offset.guitars/the-goodies/sett ... lo-system/
(it's curious that AFAIK Fender has not provided any such instructions since ~1974)

Even without a lock button, as a starting point you are trying to set the same neutral position of the screw, that should correspond roughly to the plate underneath being parallel to the top plate. Without the lock button to find and set its "easy in/east out" position, that neutral position is obviously a little more difficult to find. Many people set it to neutral and never change it again. Others like to tweak it to taste. By tightening the screw all the way you can kind of lock the trem. All of this would be much easier if the trem cavity opened to the back, like a strat's.