I broke out the C frame tool on Tuesday night to dimple two perfectly straight lines of holes that I had just drilled into some aluminum skin. Being very proud of my holes and the fact that I had deduced their accuracy and straightness down to a 1/32" I was too busy patting myself on the back to pay attention to what I was doing. Halfway through the dimple job I placed one of those new and profoundly placed holes over the die and then whacked the C frame. Suddenly my world came to a screeching halt when I lifted the female die off of the skin and found that the skin had more holes than I rememberd. Apparently the skin shifted on the C frame right before I whacked it. So now, I had a beatiful hole (that still needed dimpling) and a beautiful new hole next to it that didnt need dimpling.
Sheesh, what a good way to come off of a high. Lesson learned: Pay attention and always verify what your doing before you swing anything that looks like a mallet.
Looks like you've officially joined the RV builder's club. I made the same mistake on my empennage (one of the h-stab skins). Almost every builder I know of has done this. Watch out with the pneumatic/hand squeezer...you can easily do it with that also.
That's why it's always good to have some extra rivets around. To fill up those extra holes we all punch. Just wait till you dimple 'em on the wrong side! Been there, done that.
I've learned that when I get that feeling that all is going just peachy, is right about the same time I make some horrible mistake. So if I'm cursing and grumpy, then the work is going along well.
Remember, after using your dimple dies as a punch press you need to remove the aluminum that collects in the pit of the female die. If you don't your dies may not bottom out and form a crisp dimple.
Of course I have never had this problem but I hear in happens.