Pop rivet questions...

[peter-h]

I hope someone can give me some simple answers to a few stupid questions to do with "aviation" rivets...

There seem to be "pop" rivets, and Cherry rivets.

Cherry seem to be mostly (wholly?) rivets which leave behind a piece of the mandrel sticking out, which needs to be cleaned off, but this gives you inspectability.

Presumably the ally ones use an ally mandrel, because the rivets with steel mandrels don't leave anything sticking out.

Are there any ally rivets with an ally mandrel which don't leave anything sticking out?

Isn't there a corrosion issue with ally rivets with a steel mandrel, due to the steel which is left inside it?

Most Cherry rivets also claim to need a special tool (G-25B in most cases) which is difficult to find.

 

[Tom-D]

There a variety of pop rivets but only 1 cherry rivet.

the Cherry has a collar that locks the rivet stem in place after the stem has broken off. that collar is why you need the special driver.

Cherry rivits are approved replacement rivets in the Cessna repair manual. no pop rivet is.

When you use the proper length Cherry there is no stem sticking out.

 

[Henning]

I hope someone can give me some simple answers to a few stupid questions to do with "aviation" rivets...

There seem to be "pop" rivets, and Cherry rivets.

Cherry seem to be mostly (wholly?) rivets which leave behind a piece of the mandrel sticking out, which needs to be cleaned off, but this gives you inspectability.

Presumably the ally ones use an ally mandrel, because the rivets with steel mandrels don't leave anything sticking out.

Are there any ally rivets with an ally mandrel which don't leave anything sticking out?

Isn't there a corrosion issue with ally rivets with a steel mandrel, due to the steel which is left inside it?

Most Cherry rivets also claim to need a special tool (G-25B in most cases) which is difficult to find.

Cherry is a brand name of a cored blind rivet, it is acceptable and they make them in several mandrel and head types that pull the back flush down with a specially designed mandrel head. Pop Rivet is also a brand name of cheap uncored blind rivet that as a ball on the end and just pulls down the rivet with only thin tangential contact formed. These uncored rivets also lack stability and strength in the shear.

 

[N801BH]

Avex Rivets are used in all Zenith, Sonex, RV-12's and other aviation related projects..

Here is a brief summary of them..


http://www.zenithair.com/kit-data/ht-87-1.html

 

[peter-h]

I see two pages of different Cherry rivets in a catalogue I have here.

None of them appear to have a collar, though some have an "anvil" which rests against the rivet face and is intended to prevent damage to the rivet head from a misaligned anvil on the tool.

The main ones in use for sheet metal seem to be Cherrylock and Cherrymax, with Cherrymax available in 1/64 oversize which is desirable when replacing old rivets, AIUI.

 

[Geico266]

I see two pages of different Cherry rivets in a catalogue I have here.

None of them appear to have a collar, though some have an "anvil" which rests against the rivet face and is intended to prevent damage to the rivet head from a misaligned anvil on the tool.

The main ones in use for sheet metal seem to be Cherrylock and Cherrymax, with Cherrymax available in 1/64 oversize which is desirable when replacing old rivets, AIUI.

The "anvil" you are referring to is the "collar" the others eluded to. The "collar" ( looks like a little washer) provides a stopping point for the mandrel to seat against before it breaks flush with the top of the rivet. There is a portion of the mandrel inside the rivet that is larger than the hole in the "collar" .

The Cherry Max rivets "pop" twice, once to swell the rivet body to size, and once to break the shaft off after compressing the mandrel and rivet into one solid mass. Cherry Max rivets are structural in that they have superior shear or side strength to Avex rivets. Their mandrels are extremely hard.... try drilling they out.

They are very useful in certain applications, but cost, weight, and a slightly more difficulty in setting them properly keep them from being the pulled rivet of choice for the entire plane.

 

[flyingron]

There a variety of pop rivets but only 1 cherry rivet.

Actually that statement is wrong in a couple of ways.
Both Emhart (who own the POP trademark) and Cherry Aerospace (which owns the Cherry, CherryMax, and CherryLock trademarks) make a range of rivets for various applications.

 

[Geico266]

There a variety of pop rivets but only 1 cherry rivet.

the Cherry has a collar that locks the rivet stem in place after the stem has broken off. that collar is why you need the special driver.

You can use a regular puller if they will accept the shorter mandrel of the Cherry Max. I just competed an SB on the main gear of my RV-12 using about a 100 Cherry Max. I wasn't about to spend $100 on a puller. My pneumatic puller worked just fine when I dialed down the air pressure a little. Two distinct pops.

I went through 2 pullers that would not work until I tried my old reliable air puller.

 

[peter-h]

I had been warned against using CherryMax rivets anywhere where they might want to come out again.

I didn't realise this is because the mandrel is hard. I thought (having drilled out many pop rivets) that one just needs to drill out the head and the rest of the rivet will more or less fall out.

But the Cherry rivets seem to expand in diameter too...

This application is in thin ally; about 1mm or even less. 2 sheets of it. The current rivets are metric and for political reasons virtually unobtainable. The current rivets (I have been looking at them today) seem to have blind ends, as for pressurised hulls. The diameter has massively expanded; of the order of 1.5x.