I have been wanting a boroscope for ages. I am recently feeling like I have a few extra bob in my pocket so I took a chance on Amazon and purchased a $60 Deptech boroscope. Mainly I just wanted to keep an eye on my welding and brazing penetration out of curiosity. Being of a certain age, and notably frugal, my wife was concerned I was trying to cut our medical costs.
Here are the first few pictures - Sorry about the size.
This is inside of a nickel fillet brazed joint on a segmented fork crown. The tube with the hole in it is the steerer. There's a big fat bead around the inside which is pleasing but there are a couple spots that look like the steerer tube wasn't quite hot enough for the filler to fully wet out. It just sort of flowed through the gap and pooled up. I'm confident it's strong but, I think I can heat from the inside of the steerer to get better adhesion on this.
here's a picture of the inside of a silver lugged joint: Again, there is a clear inner fillet which is comforting.
I spent a lot of time cutting open early joints so I am pretty confident but it's nice to now have ability to check without destructive testing!