Threaded fasteners are a necessity for almost any mechanical device. When making changes to a machine, one can add threads by tapping the part itself, or by using a nut. A nut can even be welded to a part when tapping it is inconvenient or impractical. Sometimes, the material being fastened to is too thin or soft to hold threads itself, and the back is inaccessible, making use of a nut impossible. That's when thread inserts make you feel like a hero. Much like the name Kleenex(r) being used generically for facial tissues, the name Nutsert, a trademark of Avdel, is often used to cover all thread inserts. A Web search quickly yielded several competing brands and different configurations, including Thread-Sert, Well-Nut, Jack-Nut and POPnut Blind Rivet Nuts. Each has unique features making it suitable for a somewhat different range of applications, and most are available in a range of styles to meet various needs.
Here's the concept: Drill a hole, install a rivet-like device, have a set of threads. It's simple, clean and beautiful. The threads stay in place, so there are no reach-around contortions required each time the fastened object is removed or reinstalled. It works when access is available on only one side of the material, such as a frame rail or a trunk floor with an exhaust directly under it.
The tools to install these products parallel rivet-setting tools. There are fully automated, electronically monitored, precalibrated, process-controlled wonders of modern industrialization costing many hundreds of dollars. There are tools resembling a hand-held rivet tool that cost less than $20.
When I decided thread inserts were the best way to hold the Odyssey dry-cell battery into Project Rally MINI, I went to the local industrial hardware store and bought what they had. It looks like either a Nutsert or POPnut, but I don't know for sure. Either way, it worked awesome, and Sport Compact Car's Dave Coleman has also tried it and called it the "best tool in the world." The installation tool I bought then is in the photos, but I've since realized that a magic bolt box will do an even better job for nearly no money. Just thread a nut, two washers with a little grease between them and the thread insert onto a bolt. Put it in the hole, and thread the nut down the bolt to pull the insert tight.
Neuspeed has used thread inserts for strut tower brace mounting since the MkII era. Aaron Neumann told me the only real problems he's seen have been when end-users attempted to use a different size hole than the instructions called for. If the hole is too large, the insert won't grip the material. Triangular holes in thin sheet metal can also be a problem, so a Unibit ("Tool of the Month," January, 2001) can be a big help.
Chances are, you won't use many thread inserts or use them often. But when you need one, you'll be glad you know about them.