Jul 05 2010
How to Make a Good Connection Using Solderless Crimp Terminals
Crimp terminals, aka lugs, have an important place in anyone’s workbench. Fortunately, today there is a plentiful supply of quality crimp terminals and tools to use in any connection.
Terminals are manufactured in a variety of sizes to accommodate different wire sizes (known as the barrel inner diameter) and stud sizes (the hole).
If the terminal connection will be exposed to any vibration, then it is unwise to use a bare terminal. Support the wire close to, but separate from, the wire grip on the conductors. Control the flexing of the conducting strands at the point that they exit the rear of the terminal barrel.
The standard technique to add support is this: use a plastic sleeve on top of the terminal barrel – the length should be long enough to allow a second crimp which would help support the insulation.
While it is nice to have a high-end ratchet handle crimping tool, most people can not afford them for everyday crimping. The standard stamped, sheet metal, rivet jointed crimping tool that most everyone owns can be used to make a good connection if you know how. The number one rule: practice!
First, strip the outer insulation from the wire so that the ends of wire stranding should just extend out from the stud side of the crimp barrel when the ends are fully seated in the terminal. Next, center the die on the tool over the wire grip section, about 1/3 of way from the stud end to the entry end of sleeve.
Apply firm pressure on the grip, but it won’t take a great effort to achieve results. When you think you’ve got it right, tug on the wire to replicate 5-10 pounds of pressure for 22AWG wire and up to 20 pounds for 10-12AWG wire.
If you don’t know what an 8 pound pull feels like, you can create a pull test for terminal connection:
- Drive a nail into the front of your workbench
- Hang the terminal lug on the nail
- Tie a plastic gallon jug of water onto a 22AWG wire (red terminals)
- Tie 2 gallons of water onto a 18AWG wire (blue terminals)
- Tie 3 gallons of water onto a 12AWG wire (yellow terminals)
The second crimp is about 2/3 of the way along the barrel closed just enough to grip the wire’s insulation which is generally much less pressure than the amount needed to grip the wire. There are some myths out there that suggest that both the wire grip and insulation grips should be put on 90 degrees displaced from each other. This is not necessarily helpful and the technique makes for a nasty looking terminal.
Another myth is that a combination of soldering in additional to crimping will create the most reliable joints. If you are using a quality crimp terminal and testing your connection, then soldering should be totally unnecessary.
With some practice, you can easily become an expert at making good solderless crimp terminal connections.
Andy Bauer is a tech writer for http://www.westfloridacomponents.com, an internet based retailer of electronic parts and supplies.