[SJaeger10]

On my M50s I use the 1/8in jack but I am worried that the threads that the 1/4in adapter screws over will get dinged up and bent. Does anyone know of a thread protector or a good way to protect the threads?

 

[Delirious Lab]

Why not just cover it with some kind of tape?
 
I wouldn't worry about it, though.  In the unlikely event that the thread gets damaged to the point of it being impossible to screw on the adaptor, I would just discard it and use a regular adaptor instead.