Stuck screw Leica IIIf on the verge of stripping.

[MatR]

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On 11/3/2025 at 12:42 PM, qqphot said:

I wonder if there is something special about that particular screw or its location. I've seen a IIIf and a IIIg with the same screw in relatively poor or damaged condition. I didn't notice any evidence of a thread locker applied to it, but that doesn't mean there wasn't any originally. 

The reason this particular screw is often very tight and also, as a result, often damaged, is its proximity to the slow shutter speeds dial. The calibration of the slow shutter speeds is performed by loosening the tiny set screw in the "cap" of the slow shutter speeds dial, removing the cap, then loosening the central screw which is connected to the cam on the opposite side of the plate, and turning surrounding nut screw (then tightening the central screw, etc, etc, repeating if necessary, etc) . As it offsets the underlaying cam's position up or down, it changes the amount of pressure this cam (a brass colored cam on the other side of the plate) puts on the bar linking the slow speed's escapement at the bottom of the camera and the main shutter speed's cam, hence tweaking the resulting shutter speeds. This adjustment is EXTREMELY sensitive, less than a quarter turn of the nut screw under the slow speeds dial is the difference between the slow speeds working correctly and not working at all and hanging, 1 sec setting acting like a T exposure, or other way around - T exposure working like 1 or 1/2 sec instead, speeds being too short, etc -  you get the idea. Because this adjustment is made by offsetting the slow speed dial's cam position up or down (lowering or increasing the pressure it puts on the bar underneath it), therefore the plane on which the entire front plate to which the slow speeds dial is attached sits affects this adjustment. I'll mention it again - it is EXTREMELY sensitive to position changes. Over time, the brass cam being adjusted here gets warned out from normal use, the bar it puts pressure on slightly deformed - just enough to make the cam not engage enough even when set to its maximum engagement depth. Over-tightening of the screw that started this thread (no pun intended) therefore is a result of an attempt by a repair person to maximize the engagement depth, or at a minimum, to make the adjustment  stable. Because this screw is the closest to the slow speeds cam, it affects its "absolute" position the most. You may now recall a situation where loosening ANY of the screws holding the front plate affects the shutter speeds, sometimes they spring back to life magically. Sometimes it is actually even just the screws of the outer cover or the way the camera is held!