S

skyyking

Active Member
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,
 
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.
 
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 ... :D
 
I've seen that too. I've surmised that the rivet gets hot enough during squeezing that the alodine coating goes up in smoke.
 
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".
 
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).
 
Heat from Cold Working

xavierm said:
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).
Click to expand...

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
 
Would it get hot enough to dislodge the anodizing (or alodining)? If so, wouldn't that defeat the purpose of the anodization or alodine process?
 
All Rivets are ANODIZED...not alodined.

After 1991. Enough said.

And Chemical Conversion per MIL-C-5441 has nothing to do with rivets we use in todays RV aircraft.
 
The 1993 H version...

OceanBob said:
After 1991. Enough said.

And Chemical Conversion per MIL-C-5441 has nothing to do with rivets we use in todays RV aircraft.
Click to expand...

...of the MS20470 specification still calls out the Chemical Conversion

http://www.everyspec.com/MS+Specs/download.php?spec=MS20470H.008074.PDF

Did this change when the NASM20470 specification was introduced (1998), or is the part number of the rivets we think we are getting not really MS20470 AD 4-5 as an example?

Even the current Rapid Rivet and Fastener Corp Mil-Spec rivet web page lists the finish as Chemical film

http://rapidrivet.thomasnet.com/ite...10?&plpver=10&origin=advsrch&by=prod&filter=0
 
Last edited:
Definitely Anodized

After observing this smoking rivet phenomenon, I contacted Van's directly to ask what the surface finish on the rivets was. They confirmed that it is indeed an anodized coating.
 
You must log in or register to reply here.