I was hanging a ceiling fan in this room when I discovered that the mounting screw holes in the electrical box are stripped. My dad has suggested using JB Weld putty, letting it cure, drilling it out with a small bit and then using wood screws. First time homeowner and have neither the confidence nor the expertise to completely replace the box. Is my dad’s route the best course of action or is it a waste of time and/or dangerous to go that route?
You could tap the holes one size bigger and use new screws. HOWEVER, You should replace to box with a “old work” box designed for ceiling fans. Using a box that is not made to hold a fan or using the stripped holes is inviting a ceiling fan to fall on your head.
Old work boxes for fans have a bar with spikesthat extend to span the joists and drive the spike into them, this supports the weight of the fan properly.
http://mobileimages.lowes.com/productimages/7960bd4e-5fb6-4b3f-97d0-535e48ba937a/08782498.jpg?size=pdhi
edit: here is a video on how to install the old work box. https://www.youtube.com/watch?v=Hf-qKY2bRlo
Op, I'm an electrician. This comment is the best advice. All boxes used for fans need to be fan-rated. This is possible to do without attic access.
I haven't watched the video but this looks to be an okay start: https://youtu.be/DKWeyydoYTI
Just remember that ceiling fans are heavy and the little wiggle over time will cause more wear and tear than you might think.
Best of luck!