Jack - in most cases, I have seen examples where hole sizes have grown after shotpeen. I believe this to be due to overall shotpeen growth factors. It can become more pronounced where depth of hole is thin, and intensity is high (more shotpeen growth). This becomes an issue for close tolerance holes (hole size range less than .0030), where if hole is not undersized prior to shotpeen and drilled/bored to full size, then after shotpeen, hole size can grow out of tolerance. However, I have seen cases where hole sizes have shrunk. It has been at lower intensities (.004a/.007a) - I believe shotpeen growth is so small, and the apparent shrinkage could be attributed to peaks made by the shotpeen indentations only. If intensity was higher, growth would be more, and more than enough than the apparent shrinkage due to the peaks of peening indentations. I would be curious to see other examples of this from others
