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12-02-2009, 10:43 PM
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Join Date: Dec 2005
Location: Kenosha WI
Posts: 50
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smoking rivets
For you smart people out there; why does a rivet "smoke" when you set/squeeze it??
I am not referencing a previously set rivet that smokes when it is loose and working in a lap joint, leaving a trail of "smoke" on a skin; that I do know.
With much appreciation,
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12-02-2009, 11:05 PM
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Join Date: Jun 2008
Location: San Jose, CA
Posts: 113
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It is the anodized layer breaking loose from the rivet surface. The layer is brittle, so it breaks into dust size particles as it comes off.
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Steve Allison
RV-6A - sloooowwww build
First flight - 3/8/14
Phase II - 5/19/14
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12-02-2009, 11:38 PM
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Join Date: Oct 2006
Location: Melbourne, Australia
Posts: 426
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...except that rivets are not anodized. They are alodined though!
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12-02-2009, 11:55 PM
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Join Date: Oct 2009
Location: Trabuco Canyon, California
Posts: 95
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2117 rivets are anodized
Which are the most common rivet in our airplanes. (2117)
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12-03-2009, 07:11 AM
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Join Date: Mar 2005
Location: Elkhart, Indiana
Posts: 1,186
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With all of those rivets packed tightly in a box or drawer, it's no wonder that some of them become a bit amorous ... thus the smoking after squeezing.
I'm just guessing here ...
But I never seem to run out of some sizes of rivets. They seem to just come from nowhere ... 
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Don McNamara
Peoria, AZ
Builder: RV-8 "Smokey"
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12-03-2009, 08:35 AM
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Join Date: Jan 2005
Location: albuquerque, nm
Posts: 1,167
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I've seen that too. I've surmised that the rivet gets hot enough during squeezing that the alodine coating goes up in smoke.
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12-03-2009, 10:52 AM
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Join Date: Nov 2005
Posts: 1,256
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We've seen that, too, usually with -4 size rivets. It's strangely satisfying, like a Tim Allen "Ar ar AR...look at that rivet SMOKE, man!"
I always thought they were not so much heat-caused as the anodizing getting micro-fractured and flaking off as a sort of "dust".
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Steve "Flying Scotsman"
Santa Clarita, CA
PP-ASEL, ASES, Instrument Airplane
RV-7A N660WS flying!
#8,000 
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12-03-2009, 10:53 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Not unless....
Quote:
Originally Posted by OceanBob
2117 rivets are anodized
Which are the most common rivet in our airplanes. (2117)
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...they have a -A, -D or -N after the length in the part number.
The specification is here.
http://www.av8design.com/Hardware/MS20470.pdf
Standard finish (no code letter after the length) on an "AD" rivet is a Chemical Conversion per MIL-C-5441 - aka Alodine
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Last edited by az_gila : 12-03-2009 at 10:55 AM.
Reason: clarification
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12-03-2009, 02:00 PM
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Join Date: Aug 2005
Location: Los Angeles, CA
Posts: 463
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My understanding
It was my understanding that they smoke from the heat generated by quickly compressing the rivet. The compression heat changes the alloy of the rivet.
An AN470AD rivet alloy is 2117-T4. After squeezing and the resulting heat, the alloy is changes to 2117-T3 (a bit harder from being worked).
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Xavier
RV-7 build in progress
www.theaviatorx.com
" Genius is persistence in disguise"
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12-03-2009, 03:57 PM
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Join Date: Jan 2005
Posts: 1,009
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Heat from Cold Working
Quote:
Originally Posted by xavierm
It was my understanding that they smoke from the heat generated by quickly compressing the rivet. The compression heat changes the alloy of the rivet.
An AN470AD rivet alloy is 2117-T4. After squeezing and the resulting heat, the alloy is changes to 2117-T3 (a bit harder from being worked).
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Nope. The alloy doesn't change. That's the chemical composition. The temper is the designation of a thermal operation aimed at achieving certain physical properties. Try flexing a metal coat hangar quickly several times. Feel the bend point (careful, you can burn your fingers). The heat is the result of cold deformation /movement of slips planes within the crystalline structure. This takes place through "dislocations", and involves the transfer of a great deal of energy. Notice how it gets harder to flex the wire? The dislocations are "stacking up". More heat. This is typically referred to as strain hardening. For a better explanation, see the following:
http://www.cmse.ed.ac.uk/AdvMat45/CrystalBasics.pdf
Terry
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