Whilst understood well within professional harness makers, the correct application of crimps is something that doesn’t seem to be as widely understood in DIY circles with much information available ranging from not very thorough to out-rightly wrong; One of my friends was once given the advice by an employee in a car hi-fi shop to hold the crimp onto the cable with insulating tape and nothing else....... Crimping is a technique that can produce reliable, long lasting joint, efficiently and easily with very little training.
There are a vast range of crimps out there in the market- industrial users of crimps have good access to information from the crimp and tooling manufacturers so I won’t go into depth on these applications. Instead, in this Instructable I hope to give some advice on using crimps that you are likely to encounter in installing accessories or making repairs to your car, boat or caravan or in projects at home.
Much of this Instructable will focus on materials and tools, so I will split this down into detail in three main areas and will keep the introduction materials simple:
Good quality crimp terminals to suit the application
Stranded wire of a known specification (not solid core)
Good quality wire strippers
Crimp tool to suit the terminals
Step 1: Choosing the Wire
Choosing the Wire
Depending on your application, you may or may not have a choice on the wire to use. Firstly do not use solid cored wire, and if you want a reliable job heavily avoid ‘conduit wire’ (a few largish strands intended for mains buried in conduit). Specific types of crimps are required to use this type of wire reliably. The best wire for general use will be one with many strands.
Next determine the wire size- This may be listed in a number of ways, the most common being AWG (American Wire Gauge)(e.g. 16AWG), Cross sectional area in square mm (e.g. 1sqmm) or strand and diameter count (e.g. 32/0.2). There are plenty of tables around to help you convert between common sizes.
If buying new wire, the size will be listed on the reel or packet. If modifying an existing installation it may be more difficult to determine. Many wires are now either printed or moulded into the insulation with this information repeated along the length so it will be work a look to see if you can find it.
If you can’t find this information you will have to fall back to measurement and a bit of calculation. Strip back a length of the insulation and then count the number of individual wire strands and measure the diameter of one with a micrometer or vernier calliper. You can then cross refer to a table or calculate the cross sectional area by multiplying the number of strands by the area of one strand calculated by πr2.
Insulation diameter is important for the most reliable crimps as it affects how the rear of the crimp grips the wire, however as long as you use standard wires, then this should not give you a significant issue. It is however important to consider this is you are using a crimp in a professional application.