Thanks Dave, I have a pm in to Kevin Daniels at Fixe, they reccommend 12 mm. I called my brother last night and he said it would be fine, a slightly larger hole is ok though a too small hole might be a problem due to not enough glue.
Went out today and lowered down, clipped in and bounced around on it. Pulled the rope and sent it first go. My buddie Steve took 5 hard falls missing the dyno before sending, so we are pretty sure the bolt is fine.
"Napoleonic Complex," 12 a/b.
If they recommend a 12mm drill then Fixe is not really 1/2"!
mm x .03937=inches
12mm=.472", roughly 1/32 smaller than 1/2"
14mm=.550", just less than 1/16 over 1/2"
I use Bosch 17/32 bits (they actually measure 17/32, I just checked 1) and they drill a few thousands oversize. Home dumpot does not carry them. I buy them from either MSC or McMaster Carr, whoever gives me a better price. I also built a fixture to regrind bits and they are as good as new. Sometime when I am out your way I will try and hook up with you and Paula to say hi and grab some bits to sharpen for you.
The bolts I am using are the same as Mark Sprague used to use at Rumney and they measure exactly 1/2" in dia. I also use the Red head A7 glue.
In some rock the rock itself is the weak link, not the glue. Forget the shear strength of a 1/2" bolt, Nobody reading this will EVER shear one off. Red Heads tech info gives numbers for straight pullout strength with a 1/2" anchor that are staggering even in concrete which is very weak compared to rock. I wouldn't worry about that bolt!