Terminating, worked over weeks

The fourth tutorial in the curriculum. Crimping, connector assembly, lacing and bonding are hand skills, they are cheap to practice, and the artifacts show their own quality.

You need: wire of a few gauges, ring and spade terminals, a proper ratcheting crimp tool with the right dies, a connector and its insertion and removal tools, lacing cord, and a multimeter. A pair of pliers is not a crimp tool and this session will show you why.

Session 1 — The crimp, and why the tool matters

1. Crimp ten terminals with the correct ratcheting tool and die. Pull-test each one firmly.
2. Now crimp five with ordinary pliers. Pull-test those.
3. Cut one of each in half lengthwise if you can, and look at the barrel.

What you will see: the pliers crimps come off, or move. The correct crimps do not. Cut open, the good one shows the strands compressed uniformly into a solid mass; the pliers one shows a squashed tube with strands loose inside.

What you are learning: a crimp is a specified deformation, not a squeeze. The tool is the specification (AF-K Concepts §2).

Session 2 — Stripping without nicking

1. Strip twenty wires. Examine each conductor under magnification.
2. Count how many have nicked or cut strands.
3. Adjust the stripper — or your technique — and do twenty more.

What will be wrong on your first attempts:

Why it matters: a nicked strand does not fail now. It fails after some months of vibration, at the nick, and nobody will connect it to you.

Session 3 — A connector, start to finish

1. Lay out the pin assignment on paper first and label every wire.
2. Crimp the contacts.
3. Insert with the insertion tool until each clicks home.
4. Tug every wire. Any that comes back was not latched.
5. Fit sealing plugs in every unused cavity.
6. Assemble the backshell with the cable clamped.
7. Buzz it out: continuity from each wire to its intended pin, and confirm no continuity between adjacent pins.

What will be wrong: a contact not fully home, and a wire in the wrong cavity. Both are found by step 7 and by nothing else — the connector looks identical either way.

Do step 7 every time. On an aircraft it is the difference between a working system and a reversed one.

Session 4 — Lacing and bundling

1. Lace a bundle of six wires, evenly spaced, with the correct knot.
2. Clamp it to a board at intervals, with cushioned clamps at the correct tension.
3. Deliberately over-tighten one clamp and look at what it does to the insulation.

What you are learning: the clamp supports; it does not grip. An over-tightened clamp deforms insulation and creates the chafe point it was fitted to prevent.

Session 5 — Soldering, and the stress riser

1. Solder five joints, heating the work rather than the solder.
2. Deliberately make one with too much solder, and note how far the rigidity extends up the wire.
3. Deliberately move one while it cools, and look at the finish.
4. Flex each joint gently at the point where the rigid section ends.

What you will see: the over-soldered joint is stiff a long way up the wire, and that whole length is now a fatigue candidate. The disturbed one is dull and grainy.

What you are learning: the joint is rarely what fails. The wire fails just behind it, and the amount of solder decides where (AF-K Concepts §2).

Session 6 — Bonding, measured

1. Bolt two pieces of aluminum together through paint or anodizing. Measure the resistance across the joint.
2. Take it apart, clean both faces to bare metal at the contact area, reassemble. Measure again.
3. Fit a bonding jumper between two separated pieces and measure.

What you will see: the painted joint reads high — often far higher than any bonding limit. It looked like a bond throughout.

What you are learning: bonding is the one thing here with an objective numerical criterion. Measure it, every time, and do not accept a bond you have not measured.

What to send back

Record the bonding resistance you measured — the number is part of the artifact. And send the pliers-crimped terminals from Session 1 with them, so the difference is visible.

License

CC BY-SA 4.0 (Licensing).