Thread: Stanley no 3 level

stasnley 3 02.jpg I purchased a Stanley #3 28 inch adjustable level at an antique store. It was in a big bucket full of other levels, most of which were missing one or both of the vials. The wood on this one was in the best shape and both the bubble vials were there. The level bubble is just a tiny bit off but the plumb bubble is right on. The adjuster screw for the level bubble would not turn and and of course was frozen with rust. I soaked the adjuster end in vinegar over night and was able to remove the surface rust. The threads looked clean but the screw will still did not turn. I applied some penetrating oil and let that sit over night. No turning. I am reluctant to apply much pressure as the adjuster screw is small and the slot is shallow. I do not want to round it over. Should I keep on with the oil? I have thought of applying some heat with the tip of a soldering gun to see if a little expansion would free it up. This has worked for me on a couple of planes that I have rehabbed, but I do not want to break the vial if it should get too hot. I thought also I might shim the low side with a plane shaving. Has anyone rehabbed an adjustable level or have any advice or other suggestions for what can be done to free up the screw?

Thanks Dennis