a riv[e]ting topic

[Robert]

Hello All,

>
>While I was checking the spelling, I notice that wikipedia mentions
>another name for pop rivets is blind rivets.
>

I _love_ Wikipedia, but it certainly has its share of errors. Please: Never equate
pop rivets with "blind" rivets. Blind rivet is a sort of generic term -- meaning that
it's a form of rivet that can be used even though you do not have access to the other
side of the rivet. Blind rivets are used on commercial aircraft, but only in relatively small
quantities -- and -- each catagory of (blind) rivet is carefully chosen to perform a certain 
task. Most times, when we install blind fasteners (rivets fall into the broad catagory
of fasteners), we have to get Engineering approval. Most installations of blind rivets are
actually considered temporary. They will usually be removed during a Heavy Maintenance 
Visit (often several years later).

Pop rivets fall at the very bottom of the rivet catagory. Pop rivets are never used on commercial
aircraft structure, although I've used a lot of (a certain higher quality catagory of) them to fasten 
things like nutplates (all they are doing is holding what amounts to a nut, in place, while a bolt is tightened). 
Once tight, the bolt is tight the rivets are meaningless until you need to remove the bolt again. If the "pop" (type)
rivets don't hold, then a veritable stream of cursing insues, while you go and try to find the right drill bits
to remove the offending nutplates. Then, the little buggers almost always spin while you curse more and 
try to get a small pair of ViseGrips on the bottom of them (often very difficult due to space constraints), so you 
can smash them into submission, while you continue to drill them out.

"Cherry-Max" rivets are a very popular form of blind fastener (in this case, blind rivet). They have a solid
core of wickedly hard stainless steel that remains in place as the rivet is "pulled" into its compressed final
product. Not only are they relatively heavy, they do not expand in the same way that solid rivets do -- plus
you now have a dissimilar metal situation.

Speaking of pop rivets: There is a kitplane (an excellent work horse of a plane) that makes use of thousands of
closely spaced pop rivets. I used to be able to recall its name off the top of my head, but this library computer
will not allow me to open another instance of my browser (to search google and figure it out). It was a sort of ugly, boxy, utilatarian looking plane. It was so "ugly" that it was actually very cool!! It's supposedly nearly 
"indestructable."

Oh, BTW, "regular" solid aluminum rivets are only very slightly smaller than their correctly drilled, and in some
cases, reamed holes. When the are compressed (bucked), they expand and tightly fill the hole. It's certainly an
impressive art to get a properly shaped "bucked" head (also called "shop head"). If the bucked head is smashed
too much or "leans" over, you've got to remove them. Technically, you are supposed to go to the next larger
size because the material around the hole is now work hardened. If everyone actually removed ever screwed
up rivet, there would be little hope of repair at a later time (because you don't have much leeway as to size).
I'm pretty sure that that's how ships remained fairly water-tight. The final result of solid rivets are not always perfect. Upon close inspection of any commerical airliner, I can find dozens of leaking or "smoking" rivets. Technically speaking, they should be replaced. Realistically, it's a case of "what are you going to do?" I did a lightning inspection on a 757 that said they were hit on short final. It was raining and miserable (and very dark). It wasn't until the last section of inspection that I realized that I'd forgotten to check a few antennas. One thing led to 
another, and we eventually found way over 100 affected rivets (and outright holes). The plane was taken out of service for a couple of months, but I saw it again (with lots of very large rivets, which were used to "fill" some 
of the lightning strike holes).

Always choose the correct rivet for the job(!!!).

Regards,
Robert Greenstreet