New Transmission  37                 April  2012

April 15th.

Last week I was working on making new hard lines for the brakes and clutch master cylinders but now it's time to fasten them to the chassis so they stay put. To do that I brought out a tool that I don't use very often but it sure comes in handy when you need it.

When you need to put a screw into a thin wall of steel or aluminum, sometimes sheet metal screws just don't cut it. And if the wall thickness were thick enough then you could just drill and tap some threads and be done with it. But in the case of where the wall thickness is .125" (1/8) thick, a riv-nut works great. Riv-nuts are short for rivet-nut or threaded-insert (think 'pop-rivets' here and you'll get the idea).

What you see below resembles a pop-rivet gun and works like it too. Instead of installing a fastener that holds two pieces together, you're installing threads so you can screw a fastener into it. Riv-nuts are made out of aluminum and come in different thread sizes. Some of the more common sizes are: 6-32, 8-32, 10-32 and 1/4-20. I'm working with 8-32 for my hard lines which will end up holding clamps to keep the lines in place.

The threaded rod sticking out of the gun needs to be the same thread size that you're using. And it changes out in less than a minute if you need a different size. I bought mine at a company called Aircraft Spruce which has tons of items. Riv-nuts don't cost much and come in different grip ranges too.
 

 

 
I've taken out the threaded rod to show you how it works. The rod has threads on both ends but only one end has the correct size for the riv-nut that you're working with. The other end screws into the adapter that has a knob on it.

The rod on the bottom has 8-32 threads on it and so does the riv-nut next to it. All you do is remove the one and replace it with the other and you're ready to go.
 

 

 
What I do is thread the fastener on till the end of the threaded rod is flush with the riv-nut end and then leave a small gap between the riv-nut and gun. If you put the riv-nut against the gun and then squeeze it, they can be hard to remove as you unscrew it. But if that happens all you do is unscrew the locking screw at the other end, then remove the adapter and then unscrew the rod. It sounds complicated but it's not.
 

 

 
After you have the right size threaded rod in the gun, the next step is to drill a hole for the riv-nut to slide it into. After the hole has been deburred on the side that you're working from, you then screw the riv-nut onto the threads of the gun, insert it into the drilled hole and then squeeze the handle one time. Once it's been squeezed you unscrew the threaded rod out of the riv-nut and it's done.

I squeezed the bottom one to show you how it folds back on itself so you get the idea of how it works. If it were inserted into a piece of material it would have folded against the backside of it and it would be permanent. But if you want or need to remove it once it's been installed, just drill it out.
 

 

 
Here you can see that I needed a clamp in a new area as the old one wasn't in the right place anymore. After I drilled my hole and deburred it, one quick squeeze of the handle and I'm back in business. Notice how flush they sit against the surface too which helps when you're mounting something.
 

 

 
Here you can see a clamp in place which will hold the stainless line from going anywhere. These riv-nuts work so good and are so easy to install. Once you've tried them on something, it's hard to go back to sheet metal screws or some other type of fastener. And you can use them in a through hole (like you see here) or a blind hole (like fiberglass) because I've done it many times.
 

 

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