Making Threaded Rivets

[rgsparber]

Picture being on one side of a thin plate of metal and needing to have a tapped hole. The plate is too thin to tap. Furthermore, you don't have access to the other side of the plate. A great solution is to use a threaded rivet. Commercially, these are called Rivnuts. A search of the web turned up a limited number of thread sizes and a limited "crimp range". I wanted the ability to use any thread size and rivet through any thickness plate. This article explains how to make such a fastener.

If you are interested, please see

https://rick.sparber.org/ThreadedRivet.pdf

Your comments are welcome. All of us are smarter than any one of us.


Thanks,

Rick

[DIYer]

Thanks rgsparber! We've added your Threaded Rivet to our Fastening category,
as well as to your builder page: rgsparber's Homemade Tools. Your receipt:

Threaded Rivet by rgsparber

tags: rivet

[Toolmaker51]

Generally, certain Aluminum alloys can be annealed easily. 'Brush' the part with a neutral oxy-acetylene or propane torch and air cool. This is a frequent occurence in metal spinning.

[KustomsbyKent]

Rick,
Thanks for posting this, it is quite interesting.
I have significant experience in spec'ing and using Nut Inserts or nutserts in aluminum structures with hardware from #6 up to 1/2" hardware and in thicknesses from 0.050 to .375".
What you propose for making your own inserts is probably fine for up to ~#10 size of fastener. Past that, the bolt strengths and application uses becomes a bit more critical where a person could get into unsafe conditions quickly.
We were using aluminum rivnuts for only the very small hardware, like #6. Any larger, and they were always steel nutserts with significant holding power.
The backing washer/backing plate is important for a few reasons: 1. to hit the right grip range, and 2. spread out the load in the relatively thin sheet stock.
The threads themselves are important as well:
These are inserted using a spin-spin technique or a spin-pull technique. Most smaller nutserts use a spin-spin method where you spin the nutsert onto the mandrel, and then the mandrel spins to collapse the nutsert. During that operation, the threads must withstand significant torque and not strip out. Also, the mandrel must be a hardened fastener to take more than one cycle.
There are spin-spin nutsert guns that are setup with the particular size mandrel, and used for high speed inserting. Total cycle time from start to finish is 10 secs.
For the larger nutserts, like 3/8" and 1/2", it is better to use a spin-pull method, where the nutsert is spun onto the mandrel, then inserted into the hole, and the mandrel pulls up to collapse the nutsert. These are much better on the threads, and the mandrels last much longer. The tools are expensive though, approaching $10,000 for production tools!!! I know most of us aren't going to spend that kind of money for our hobby projects, so a spin-spin method is fine.
When the nutsert collapses and forms that ring, it is important that the nutsert does not tip off to the side.. if it does, it is junk and needs to be drilled out and replaced. The hole tolerance needs to be as tight as possible, so that the nutsert doesn't swell too much before it collapses.
I just got done putting in some 3/8" nutserts on the ramp assembly on my All Terrain Track Chair project, and I used a manual method for putting in those nutserts. It took about 5 mins to do one insert, so after putting in 12 of them, an hour had passed!
In production, we would have production folks putting in hundreds of nutserts an hour using the expensive nutsert guns.

Here's a video showing the nutserts I just put in, and I explain a bit about the process as well, skip ahead to ~2:39 in the video:

So, I do support the method you show for making these, but just exercise caution and keep it to #10 and smaller nutserts for safety.
Thanks for sharing!
Kent

[rgsparber]

Kent,

Your insights are most welcome! I have updated the article with a warning about the maximum bolt size plus explained the importance of a backing washer for thin stock. I also added you to the acknowledgment section.

All of us are smarter than any one of us.

Rick

[rgsparber]

Toolmaker51,

Thanks for the tip! I have added it to the article plus put you in the acknowledgment section.

Rick