While the shop heads may be a little thin, I think the majority, if not all of them, would actually be okay from a structural standpoint.
Alcoa (Think it was them) did a bunch of tests way-back-when to determine how much strength was lost from poorly and mis-set driven rivets, where it was determined even what we would view as shockingly bad rivets, rivets with cracked heads, etc, were still within 5% of the strongest properly-set rivet. Can't remember where I read it, but I'll try to find it.
In my mind, you're likely to do more damage drilling out a long line of rivets and replacing all of them than leaving them as-is.
EDIT: Haven't found the article yet, but multiple quotes from it:
Quote:
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Originally Posted by Alcoa Aluminum Rivet Book, dated 1984
"The standards to which driven rivets should conform are frequently uncertain. In addition to dimensions and perfection of shape, inspection is concerned with whether the drive head is coaxial with the shank (not “clinched”) and whether there is excessive cracking of the heads. It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength, fatigue strength and resistance to corrosion. (Poorly set and cracked) rivet heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five per cent of the strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole is likely to be more defective than the first because the hole is enlarged and rivet will be more likely to buckle and form an imperfect head.
Tests have shown that very small rivet heads are sufficient to develop the strength of the rivet shank, even when the rivets are subject to a straight tensile pull….where a large head is not needed for appearance, smaller sizes of drive head should be used to decrease the required driving pressures.
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And a quote from
another VAF'er regarding poorly-set rivets:
Quote:
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Originally Posted by Michael Burbidge
Here's the advice I received from Vans technical support when I asked them whether I should go to the next size rivet or not.
"Our advice is to never drill out a rivet unless you have to take the assembly apart. No matter how ugly it is, it probably has 90% the strength of a perfect rivet."
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