People... Tap your holes halfway thru when you first build the kit. You wont have a need to over tighten because it's hard to differentiate between forming threads and when its tight, which results in over tightening of these small screws and/or stripping the plastic. Cut threads in the plastic and the screws go right in easily and pull tight to a torque you can feel and then stop.
m3x.5 is a much finer thread than #4-40, actually 20% finer, and doesn't grip plastic formed threads as well. But public demands metric! lol
Torque values for M3x.5 screws:
M3x.5 steel button head cap screw torque (into aluminum thread) 1.25 nm
M3x.5 steel button head cap screw torque (into plastic thread) 0.32 nm
Yeah, that's not a typo!
Remember, don't run the tap all the way thru the hole. Trick is to tap about half the way through the thread (best guess estimate is fine here). Commonly used screws and turnbuckles can be lubed with chapstick for easy movement.
Mildly Tight is good, really tight is stuck and over tight is stripped and probably broken or soon to be.
Screws shouldn't back out of a cut plastic thread on their own. Screws in aluminum threads may require a SMALL amount of BLUE thread lock the first time they are installed.
If you have a LOCK TIGHTED screw that doesn't want to come loose with reasonable force, stop! heat the head with the tip of your soldiering iron for 30 sec. this will break the lock tight free and usually allow the screw to come right out. If you try to force it the hex will round out and require a dremel.
Just a little FYI.
BK