Public service announcement, Ruvnuts, dont make this mistake

[Angrey]

So I bought a rivnut tool with nuts that you see on Amazon, ebay, etc.

I'm installing a set of canards and needed it for that, but wanted it for future stuff too.

The canards arrived and I had already purchased the black anodized M5 bolts. The canards came with what's called a slotted nut, rather than the shorter, typical ribbed nuts that come with most rivnut tools.

Well, the proper pilot hole for an M5 is about 1/4", so I measured and drilled. Getting ready to use the tool for the first time, the slotted nuts are slightly bigger diameter than the same M5 ribbed nuts. So I enlarged the pilot hole.

I went to compress the first rivet and discovered that the mandrel tip is not long enough to get a bite on the slotted nut threads. However, it was too late to go back to the shorter rib nuts because the pilot hole was now too big. Well shit.

I went searching the ends of the internet to find a longer M5 mandrel. After exhausting my search, I came across a set of the manual rivnut tools and after receiving them, they're what I should have purchased in the first place.

Not only do they store in a much smaller footprint, the mandrel tips are long enough to compress the larger style nut offerings. They can be used with a ratchet or a power tool for infinite "stroke" length (as the inferior tool calls it and has to be preset with limitations).

The manual set also can be used in much more confined spaces (like under a car, inside an engine bay, etc. The plier style giant tool needs basically a free and clear space at least 3 feet wide and several feet away from the rivet location (for the tool, you and enough distance to get proper leverage).

Additionally, there's less worry about if you're compressing it at an off angle.

All in all the manual tools are just a better, more useful and slightly cheaper tool. Skip the giant bolt cutter looking device and get the manuals instead.

Sponsored

 

[PVAMT]

The ones I use in aviation are the size of a normal pop rivit gun and far easier to use. I also have a set of the manual type that you can get longer bolts for if needed. They’re great in tight spots.

 

[shogun32]

using well nuts might be easier/better still. Does depend how strong you need the joint to be.

 

[Evolvd]

I’m looking to install some rivnuts in a carbon fiber s-wing I picked up as it has no mount holes for the gurney flap. I have no experience with rivets or rivnuts so I have no idea which ones to get for carbon fiber that won’t crack the composite. I found a company that makes rivnuts specifically for CF but I cannot find anyone that sells them in small batch or singles. If I wanted 100k of them that would be easy lol.

 

[PVAMT]

If you don’t want the slotted riv-nuts ask for aviation riv-nuts.

 

[Angrey]

I’m looking to install some rivnuts in a carbon fiber s-wing I picked up as it has no mount holes for the gurney flap. I have no experience with rivets or rivnuts so I have no idea which ones to get for carbon fiber that won’t crack the composite. I found a company that makes rivnuts specifically for CF but I cannot find anyone that sells them in small batch or singles. If I wanted 100k of them that would be easy lol.

I think you're misunderstanding the concept.

The nut itself crushes around whatever sheet material you've piloted a hole. It has a flange on the outside and as you pull the threads in it creates a bulge or sandwich on the backside.

If you can pilot a clean hole in the material, it'll work. It then becomes how big of a flange on the front side and how big of a bulge section on the backside you need to grab enough material to not fail once you've screwed into it and applied a load.

Assuming it's not extremely thick, I think just about any of the common rivnut types would work.

 

[shogun32]

If you don’t want the slotted riv-nuts ask for aviation riv-nuts.

https://www.aircraftspruce.com/menus/ha/rivetnuts.html

 

[PVAMT]

https://www.aircraftspruce.com/menus/ha/rivetnuts.html

How many do you need and what size? I can check what I have in my toolbox

 

[PVAMT]

How many do you need and what size? I can check what I have in my toolbox

If I don’t have the size you need go with the flat head ones

 

[Evolvd]

I think you're misunderstanding the concept.

The nut itself crushes around whatever sheet material you've piloted a hole. It has a flange on the outside and as you pull the threads in it creates a bulge or sandwich on the backside.

If you can pilot a clean hole in the material, it'll work. It then becomes how big of a flange on the front side and how big of a bulge section on the backside you need to grab enough material to not fail once you've screwed into it and applied a load.

Assuming it's not extremely thick, I think just about any of the common rivnut types would work.

Actually I completely understand the concept, my concern is how much pressure is there between the flange and the bulge when installing it. If I was installing into a steel sheet metal skin I wouldn’t worry about it, but for a carbon composite you can’t just go willy nilly with the compression between the bulge and flange.

 

[Angrey]

Actually I completely understand the concept, my concern is how much pressure is there between the flange and the bulge when installing it. If I was installing into a steel sheet metal skin I wouldn’t worry about it, but for a carbon composite you can’t just go willy nilly with the compression between the bulge and flange.

I haven't seen the material strength report for your composite, but I have to believe it's stronger than ABS and that's what I and others are riveting into for dive planes and canards.

If you're that concerned, use the slotted nuts I references, they birdcage instead of bulging (very similar to many drywall anchors) so it'll be minimal stress on the substrate material.

I think they're called "jack nuts"

"Will not distort or deform soft plastics or sheet metals"

Hillman 59126 Short Jack Nuts (1/4"-20) - 15 Pieces - - Amazon.com

 

[shogun32]

For small canards and light-weight fixture Well Nuts are rubber and used with 1-2mm thick lexan and ABS plastic. And the nice thing about well nuts is they are easily removable. Not so the all-metal variety.

 

[WD Pro]

So I bought a rivnut tool with nuts that you see on Amazon, ebay, etc.

I'm installing a set of canards and needed it for that, but wanted it for future stuff too.

The canards arrived and I had already purchased the black anodized M5 bolts. The canards came with what's called a slotted nut, rather than the shorter, typical ribbed nuts that come with most rivnut tools.

Well, the proper pilot hole for an M5 is about 1/4", so I measured and drilled. Getting ready to use the tool for the first time, the slotted nuts are slightly bigger diameter than the same M5 ribbed nuts. So I enlarged the pilot hole.

I went to compress the first rivet and discovered that the mandrel tip is not long enough to get a bite on the slotted nut threads. However, it was too late to go back to the shorter rib nuts because the pilot hole was now too big. Well shit.

I went searching the ends of the internet to find a longer M5 mandrel. After exhausting my search, I came across a set of the manual rivnut tools and after receiving them, they're what I should have purchased in the first place.

Not only do they store in a much smaller footprint, the mandrel tips are long enough to compress the larger style nut offerings. They can be used with a ratchet or a power tool for infinite "stroke" length (as the inferior tool calls it and has to be preset with limitations).

The manual set also can be used in much more confined spaces (like under a car, inside an engine bay, etc. The plier style giant tool needs basically a free and clear space at least 3 feet wide and several feet away from the rivet location (for the tool, you and enough distance to get proper leverage).

Additionally, there's less worry about if you're compressing it at an off angle.

All in all the manual tools are just a better, more useful and slightly cheaper tool. Skip the giant bolt cutter looking device and get the manuals instead.

I think my M5 rivnuts needed a 8mm hole ?

Anyhow, a quick release wheel skewer from a push bike and some tubing can be used to start the compression of a M5 rivnut (especially the slotted type).

I believe they can also be set with a nut, bolt and washer

Actually I completely understand the concept, my concern is how much pressure is there between the flange and the bulge when installing it. If I was installing into a steel sheet metal skin I wouldn’t worry about it, but for a carbon composite you can’t just go willy nilly with the compression between the bulge and flange.

I am sure other will prove me wrong, but personally I wouldn’t fit them into a thin composite as I would be worried about the propagation of cracks, particularly after a few stress cycles or in later life. If possible, I would choose rubber rivets / well nuts

WD

 

[Evolvd]

I think my M5 rivnuts needed a 8mm hole ?

Anyhow, a quick release wheel skewer from a push bike and some tubing can be used to start the compression of a M5 rivnut (especially the slotted type).

I believe they can also be set with a nut, bolt and washer



I am sure other will prove me wrong, but personally I wouldn’t fit them into a thin composite as I would be worried about the propagation of cracks, particularly after a few stress cycles or in later life. If possible, I would choose rubber rivets / well nuts

WD

I’m pretty sure the forged swing is a skin and the bottom trunk mount holes are quite thick. I really won’t know until I drill into it. I found a company that makes rivnuts specifically for composite applications, but so far I haven’t had any luck finding a distributor that doesn’t require a 10k piece bulk sale

Sponsored