I would consider the following to be the minimum required tools to fabricate a high quality, reliable harness. Like any other part of your airplane build, using good quality tools will pay dividends in reduced frustration and increased quality of workmanship.
1. WIRE CUTTER
Any decent quality wire cutter will be fine, as long as it makes a clean, square cut and doesn’t crush the wire. Small electronics flush cutters like the Hakko CHP-170 (Hakko / Amazon) are ideal. These are also handy for cleanly clipping cable ties and lacing cord in tight places.
Hakko_CHP-170.jpg
2. WIRE STRIPPER
The key here is to use a stripper that cleanly cuts the insulation from the wire but doesn’t nick any of the wire strands. The wire typically used in aircraft (see Part 2: Materials) has insulation that can be difficult to strip cleanly with a poor stripping tool. My recommendation is the Ideal Industries Stripmaster.
Ideal_Stripmaster.jpg
Look for model 45-092 (10-22AWG) or 45-093 (14-22AWG). Replacement blade sets are available to strip wire sizes from 8 to 30AWG in various combinations, and the blades are quick and easy to swap. Used tools are often available on eBay at good prices, perhaps needing a blade set to work like new for the wire sizes you want.
3. D-SUB CRIMPER
Tool P/N Blade Set P/N AWG Crimped 45-090 L-4419 8, 10, 12 45-091 L-4420 10, 12, 14, 16, 18 45-092 L-4421 10, 12, 14, 16, 18, 20, 22 45-093 L-4422 14, 16, 18, 20, 22 45-097 L-4994 16, 18, 20, 22 45-098 L-5361 20, 22, 24, 26, 28, 30 45-099 L-8763 8, 10, 16, 18
You can spend many hundreds of dollars on tooling to crimp d-sub pins and sockets, but it’s definitely not necessary. Note that we’re going to be using turned contacts, not stamped-and-formed (I’ll explain why in Part 2). This means you want the 4-way indent type of crimper with a rounded head, not the type with replaceable dies in jaws that hinge open. I use a clone of the Greenlee or Paladin PA1460 that I got on Amazon for $27, and it works perfectly.
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4. D-SUB PIN EXTRACTOR
Inserting a pin or socket in the wrong connector cavity isn’t matter of if, it’s a matter of when and how often. This is one place where the cheap tool will drive you into a purple-faced rage. Avoid, at all costs, buying the tiny red and white plastic tool with the metal probes at each end. The metal in those things is thin and flimsy so it will break after a few uses, and it’s very easy to stab your hand with the other end while using it.
Bad_Extractor_Tool.jpg
Avoid this tool!
Instead, I would strongly recommend buying the Harting Electronics 09990000368 D-Sub Removal & Insertion Tool (Digi-Key / Mouser / eBay). The business end of this tool is made of stouter material, it has a handle big enough for human hands, and the retractable probe cover will protect the tool between uses. Even at $30, this little tool is a bargain. It can still be bent, so don’t go full gorilla on it.
Harting_09990000368.jpg
This is the tool you want.
5. HEAT GUN
Any model will do, and you’ll finally get to use that strange curved attachment that came with it.
6. LABEL PRINTER
You can get a decent electronic label printer at any office supply store or online for not much money, so there’s no reason not to clearly label your wires and harnesses. If you use printable heat shrink tubing, you can label individual wires directly, and you can use standard label tape to mark harness connector backshells. Virtually all of the label printers on the market have refill cartridges available with either label tape or heat shrink.