Originally Posted by 1der
Those pre-bulbed nuts are also known as Plus-Nuts. They are a very nice way of creating secure fastening points. They are available in at least two different spec ranges depending on thickness of the material they are being inserted into.
A special tool is required for setting any of these types of “blind” nuts. The plus nuts usually require a slightly longer bolt than a RivNut.
Once upon a time there were rather inexpensive but effective parts I bought to set these nuts with nothing more than a Grade 5 or 8 hex bolt and a few sacrificial washers---I can't seem to find them on McMaster any longer--odd because that's where I originally found them.
The more sophisticated (and expensive) tools aren't necessary unless we're using these sorts of fasteners in a production-like situation. The manual setting tools are fine for what most of us would be doing.
What I like about them is their fairly spectacular holding power when installed in something like our interior ribs. The huge backside mushroomed bearing surface is nearly impossible to pull out unlike the typical rivet nuts. In fact in my work van that suffered a rear end collision that sent a lot of tools flying and broke a few of my Snap On tool box drawer locks everything attached to the van via the Plus Nuts was not affected one bit. Not a single sign of stress or strain showing on any part of the assembly where they were a part.
Glad to see a few of us already familiar with these.