So, let me just start with this: We've learned our lesson. Please just make it better this one time and I swear niether of us will do it ever again.
My son, 13, was cleaning his Yamaha 5335S and a bottom valve cap was stuck. So, without coming to me for help, he got out pliers to take it off (strike one). It gets a little unclear at this point but I think what happened was when it let loose the pliers slipped and banged the neighboring valve casing at the threads (strike two), again without telling me he attempts to fix it with the pliers, leaving a flat spot where the casing is out of round (strike three).
At this point he brings it to me and gets a lecture about asking for help and taking it to a pro if neccessary. Which advice I immediately begin to ignore myself and attemp to fix it (I know we're past three strikes here, but just go with it). So I decide to tap a a cone (actually a cake decorating tip) into the valve casing to true it up. Great success! The valve casing was perfectly round, and there was much rejoicing. Which rejoicing was short lived when we attempted to replace the bottom cap. The tapping had ever so slightly expanded the threads so the valve cap would not fit. We attempted to heat the cap to get it on but cut our losses after that.
The good news is that the horn plays fine without the cap. The bad news is it looks bad and of course it is the third valve witch is most visible. It is only the bottom one-two threads that are stretched. How difficult a repair is this going to be?
We have a tech that works intermittently out of a music shop in our small town but I haven't always been impressed with his work. Down the road an hour in Springfield (MO) there is a much better tech. I'd rather not make the trip twice and have him be without the horn for a long time.
What are your thoughts?