position of rivet mfgr head

[mackra]

I have not used rivets or riveted nut plates in previous designs, so asking a stupid question. Referring to the image below, I believe it's common or recommended practice to orient the rivet such that the shop head is on the nut plate (B). Is it 'permissible' to have the mfgr head on the nut plate (A) instead of the shop head? For this application the sheet and rivets are CRES.

edited -
The rivets are universal head.
The nut plates are fixed double lug.
Thanks

Edited to include image below.

No surfaces are exposed to air flow( ie air craft skin).

 

[SWComposites]

Isnt the shop head protruding and the manufactured head countersunk? So they cant be reversed?

 

[rb1957]

I think "nut plate" may mean an anchor nut ? These are generally installed (pretty much the only way they can be) with the CSK shop head on the far side (relative to the anchor nut).

That said you "can" buck into rivet tail into the CSK and micro-shave flush ... a manufactured CSK head.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[mackra]

SWComp - The rivets are universal head, so while they can be flipped, it may not be common practice or recommended.

rb1957 - These nut plates are fixed double lug.

 

[rb1957]

post a pic

but if you've got a protruding head rivet, it really doesn't matter which side the shop head is on.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

Ok, so is this a generic question? Or an MRB issue? What is required by your fastener install process spec?

And yes, pls post a picture/figure.

 

[mackra]

Yeah, pictures = 1000 words. I'll have to draw something up to post here, what I'm working on is proprietary. I think this would be considered a general usage question. But since I haven't used rivets in past designs, I'm afraid I'm a bit of a newbie, ha.

One reason that I can think of that the shop head should be on the nut plat side instead of the base material is that the nut plate would provide support as the shop head is being formed. Similar to using a washer on a blind/pop rivet. The mfgr head (universal) being wider distributes the load, whereas the shop head on base material is a smaller area to distribute load.

I'll work on getting something sketched/modeled and post.

Thanks for everyone input.

 

[RoarkS]

Yo what he's saying makes total sense. (I keep an A&P card in my wallet)

I install a lot of inspection plates in aluminum.

Typically I put the nutplates in using a 426 (c-sink) manufactured head in the skin and form the bucked end (shop head) on the nutplate. I usually use a pneumatic squeezer with reduced diameter dies so as to not squish the floating portion of the nutplates (if you're using floaters).

Typically you use the same convention as with bolts... Manufactured head UP or Forward... "out" if on a skin. You usually don't want a shop head in the airstream. The only exception I can think of is if you're bucking the shop head into a countersink and you're going to rivet shave it. Not ideal... but I've seen it.

TLDR: I can't think of a case where I've put the manufactured head on the nutplate. Is it wrong... no, but what's on the other side?

 

[Sparweb]

You can make a case for the physical assembly, if you take care of enough details, that you can assemble the anchor nut this way. But it would be pointless to do so, no matter how much hot air you blow on it. Costs a lot more, take more time, etc. Not a win for your manufacturing team.

The anchor nut is there to provide part of a fastener assembly. Fasteners are used to join parts together, and those parts will come into contact with each others' surfaces during the fastening process. boy I love explaining the obvious. But at the moment those parts come in contact with each other, then why the heck would you have rivet tails sticking out?? Even if you did go to all the effort of flushing out the surface with countersinks and bucking carefully and shaving down the excess, you're still going to have a bit of protruding rivet tail sticking out half the time. Even if it's only 1/2 thou, it's not a smooth surface, and you spent extra time and energy making it that way. Imperfect paint adhesion, a couple of gouges where the shaving tool slipped, scratches during assembly... it's not pretty.

Anchor nuts imply a lack of access to the anchor-nut side of the part, not the other way around. Well then don't go installing the anchor nuts with a method that demands maximum access to the anchor nut side of the part - and forces extra access to the outer face of the part to clean up the rivet's shop-head.

If you're struggling with an assembly issue of some sort, look up "Cherry CCR rivets".

 

[mackra]

Hi,
I've updated the OP with an image to clarify my question about orientation of subject rivet(s). (B) is most common, is (A) acceptable/allowed?

 

[WKTaylor]

There are CRES blind rivets intended for nutplate installs, as previously described.

Reverse install is done sometimes due to limited accessibility [head or tail]?

Bucking on a protruding head on side A... and setting the bucked-tail into a countersink on side B is 'the NACA method'. Doing the opposite install, IE: bucking on the tail and using a bucking-bar on the head... is trickier... requires a bar with a protruding head 'set' [to match the rivet head] hard-mounted on the edge of the bar. These odd methods require practice and skill.

Bucking solid SStl [annealed?] rivets into SStl is not easy... especially as You are describing. Requires lots of force, vibration, etc. IF ABLE suggest set rivets by 'squeezing'.

You have not mentioned...

What NP part number. Normal rivet spacing or reduced rivet spacing?

Is the NP install 'wet' with primer or sealant?

What is the environment that the NP install is intended for: high heat or fire? sonic? exposed to external environment, IE: water, salts, oils, fuel, abrasion, etc.

What is the mating fastener and torque... type/alloy/etc?

What is the NP holding together and what is the 'stack-up depth' [=fastener length?]?

There are NPs that are adhesively bonded in-place... primarily for aluminum or composite structure ['Click-Bond' comes to mind]... but the NP, adhesives, etc have to be matched to structures, environment and applications.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

While walking the dog tonight... Duhhh...

Solid Monel [CuNi, MS20615M(MP)] rivets are somewhat easier to drive or squeeze than SStl [3xx A, MS20613*C*]. Likewise Monel blind Rivets for NPs [many PNs]

Solid A286 [NAS1198M] are difficult [squeeze]... but have high strength and high-temp properties.

Also solid Titanium Columbium [TiCb, MS20470T] rivets are also somewhat easier to drive or squeeze than SStl.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[SWComposites]

B is not most common. As sparweb states above there is a mating part that has to be flush with the skin; the head you show will interfere.

There needs to be a countersink/flush head on the bottom.

B might be common with a flush head rivet.

 

[RoarkS]

I cant think of a case where I've put in a nutplate with a 470. I'm not due back at work for another month but I'll keep an eye out.
I would call B normal if it were a 426 c-sink.
I've never seen A with a 470 universal that I can think of.

I put 6x MS21059L3's on a 2024-T3 .040 thick doubler held on with MS20426AD3 rivets with the C-sink machined in the doubler if the skin is too thin to support the C-sink. The cover plate is usually held on with AN525-1032R8. Installed with a CP214 with reduced diameter dies.

 

[rb1957]

on your sketch, is the mating part flush with the lower surface ? Obviously it can't be (because of the protruding heads, or tails).

Please show the mating part (cause I can't make sense of it).

In my experience, a/nuts are usually installed with CSK rivets, be they full head (20426) of reduced head (1097). And, yes, the manufactured (CSK) head is on the part, on the mating surface, and the shop head is formed on the a/nut flange. You could have a protruding manufactured head on the a/nut flange, and buck the tail into the CSK and shave flush ... but not typically.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[BragiBaldursson]

You can do as you please although more common is to use countersunk rivets and buck against the nut plate. Or you can use these and will need no rivets.

https://www.clickbond.com/products/nutplates/