By Andrew Womack, EAA 619558
In 1948, Cleveland Pneumatic Tool Co. applied for a patent “related to a fastener for temporarily holding together perforated plates in perforate alignment, preparatory to the riveting thereof,” subsequently known as the Cleco. This amazing little device allows companies and individuals to manufacture and assemble aircraft, along with anything else that needs two sheets of thin metal joined together. Anyone who has used these temporary fasteners using the small plier tool that goes with them soon learns that there is a price to pay for a full day of assembling parts. This was the case with my father and me. We started the adventure of building an airplane on the little farm I was raised on, which has a grass strip, and where my mom and dad still lived. I lived an hour and a half away so I would visit every weekend and we would work on the airplane. It was a Zenith CH 701, which is an excellent kit and very straightforward to build. The build required you to assemble the parts temporarily and match drill all the holes, which means leave half the holes open, drill them, then relocate the Clecos to the drilled holes, then drill the remaining.
You then remove all the Clecos, debur the holes, and prime (if desired), reassemble again with the Clecos and start riveting, eventually removing the Clecos as you go. That is a lot of plier squeezes. My dad would do most of the assembly during the week, then I would come down on weekends and disassemble, prime, reassemble, rivet, etc. The rudder and tail section went quick, but as we started on the wings, things began to slow down. My dad mentioned he was having issues installing the Clecos, which is not surprising since the wings have significantly more Clecos. My dad, who was almost 80, made it clear to me that he was still strong enough to collapse the Clecos with the pliers, he just could not hold it long enough and keep that squeeze while reaching and placing it into the hole. It occurred to me that we needed a better pair of pliers. One that you squeezed once to lock in place, then released after the Cleco is placed. This turned out not to be as easy as I initially thought. We eventually started using an air-actuated Cleco tool, which my dad was never happy with, mainly because he had to deal with the hose, compressor, etc. I began designing a prototype of the latching pliers, however it did not happen within the time my dad had left, as he died before we could finish the airplane (and the pliers). Of course, other things in life also got in the way as I took an overseas assignment which slowed the progress on the airplane, but did give me extra time with my 3D printer to work out the design of the new Cleco pliers. Once I felt I had an acceptable design, I made a pair from aluminum.
So, after 75 years, we now have an upgraded pair of Cleco pliers. Pliers are levers, so when I started to design these, I wanted the latch located at the furthest point from the pivot (fulcrum). This would allow for the least amount of force required for the latch to hold. The reason I thought this was important is that the more force the latch needed to hold, the beefier it had to be, hence heavier materials would be required. The design looks simple on the outside, but to be reliable it took a bit more design work on the inside, specifically the pivot area. The special design keeps the rear of the plier handles in complete alignment, so the latch mechanism always finds its mark. The latch is simple, but more importantly, it can be released without moving the pliers in your hand or having to use both hands. Just a slight squeeze and flick of your pinky finger or thumb will release the latch. I have also found the approach to the Cleco from the front of the pliers, like on the conventional pliers, was not as convenient as from the side. The side approach allows for a slight rotation of the wrist to capture or release the Cleco, where the front requires even your shoulder to get involved.
Another nice feature is the handles are at least twice the width of the standard Cleco pliers so the contact pressure against your hand is at least half. They are also made of aluminum which means they are lighter than the regular Cleco pliers. And finally, the things I like the best are the capture magnets that can pick up the Cleco and automatically position it in place until you are ready to collapse it and place it into the part. It allows you to hold your parts together with one hand while you use the pliers to snatch up Clecos and place them in the part. The Clecos practically jump off the work bench (and sometimes the floor) into the pliers.
Thanks to these pliers, I plan on many more years of airplane building.
YouTube Video Link: Latching Pliers for temporary fasteners (Clecos)