Note
Cleco Sizes and Colours Decoded, and How Many You Actually Need
The colour code, what each size fits, and an honest answer to how many clecos a build needs, which is more than you think and fewer than the internet says.
Clecos are the least glamorous tool in sheet metal work and the one that most changes whether a day goes well. They are spring loaded temporary fasteners that hold two sheets in register while you drill, deburr and rivet.
The colour code
Clecos are colour coded by hole size, and once you know the code you never read one again.
| Colour | Hole | Drill | Rivet |
|---|---|---|---|
| Silver | 3/32 in | #40 | 3/32 in |
| Copper | 1/8 in | #30 | 1/8 in |
| Black | 5/32 in | #21 | 5/32 in |
| Brass or gold | 3/16 in | #11 | 3/16 in |
Silver and copper cover the overwhelming majority of light aircraft work. Note that some suppliers reverse silver and copper in their listings, so check the stated hole size rather than trusting the colour on an unfamiliar brand, and standardise on one brand once you have one that works.
Our cleco listings state the hole size and the colour on every line for exactly that reason.
You cannot fit them by hand
Clecos are compressed by cleco pliers, which fit every size. There is no technique that avoids them. At 13 EUR ex VAT this is not a decision, and a second pair is worth having so two people can work, or so one can be at each end of a long skin.
How many
The honest answer is more than a beginner expects. The standard practice for a skin is a cleco in every third or fourth hole, which on a wing skin with several hundred holes is a lot of clecos.
Practical guidance:
- Small repairs and brackets: 25 to 50, mostly copper.
- A kit aircraft build: 100 minimum, and 200 will be used. Split roughly evenly between silver and copper, weighted to whatever your plans specify.
- A production shop: per station, and expect to lose some.
A 100 piece kit with pliers and a case at 118 EUR ex VAT is the sensible starting point, and individual clecos are available singly from 0.95 EUR with a minimum of ten, because nobody needs one.
Why the case matters more than it sounds
A hundred small spring loaded steel objects, in a hangar, is a FOD source. Clecos are exactly the size and shape that ends up in an airframe, on an apron or in an engine intake, and they are easy to drop and hard to notice.
Keep them in a container, count them if the work is inside a structure you are about to close, and if the case travels to an aircraft it is worth cutting foam with a pocket per group so a short count is visible rather than counted. That is not overkill for a hundred loose fasteners going airside.
The mistakes worth avoiding
Using the wrong size in a hole. A silver cleco in a 1/8 inch hole does not grip and lets the sheets move, which is worse than no cleco because you will trust it.
Leaving them in too long during priming or painting. They mask exactly where you need coverage.
Using worn clecos on final assembly. The spring weakens with cycles and a weak cleco lets the sheets separate slightly, which is where a gap between skins comes from. If it does not snap crisply, retire it.
Assuming they are all the size you last used. Sort them back into the case by colour. Digging through a mixed pile is where the time you saved goes.