Introduction: Selecting the right wire crimping tools and terminals is crucial for a safe, durable electrical connection. A common question for DIYers and professionals alike is when to use insulated vs. non-insulated crimp terminals and how the crimping technique differs for each. In this blog, we’ll break down the key differences, preparation steps (wire size, strip length, fit), and even map some product solutions from Haisstronica’s catalog. By the end, you’ll know exactly which wire crimping tool to reach for – whether you’re crimping a wire to an insulated vinyl connector or securing a bare non-insulated lug – and how to crimp wires properly with each type for reliable results.
The Short Answer — When to Choose Each, and How Crimping Differs
When to use non-insulated vs. insulated? In a nutshell, non-insulated crimp terminals are best when electrical isolation isn’t a concern (e.g. inside a controlled panel or for a ground connection) and you want a compact, economical solution. They’re simply bare metal connectors, so they’re smaller and cheaper – ideal if you plan to add your own insulation (like heat shrink) or if the connection is in a low-risk location. On the other hand, insulated crimp terminals (vinyl, nylon, or heat-shrink types) are preferred whenever there’s any chance of shorts or environmental exposure. Their built-in insulation protects against accidental contact and moisture, which is critical if the wire might touch other conductors or face vibration, chemicals, or weather. For example, if a “hot” wire runs next to other wires, using an insulated connector prevents dangerous shorts by covering the crimp barrel. In short, use non-insulated terminals only when additional insulation isn’t needed, and use insulated terminals for everything else to be safe.
How does crimping differ? The act of crimping – using a wire crimper tool to compress the terminal onto the wire – differs mainly in the crimping die design and technique for each type. Non-insulated crimping tools often have a sharpened indent or “nubbing” on the die that bites into the barrel for a tight crimp. This creates a firm mechanical lock on the bare metal, but it would puncture or damage an insulated terminal’s plastic sleeve if used incorrectly. That’s why dedicated insulated terminal crimpers use a different jaw profile – typically a rounded or oval crimp that squeezes the internal metal ferrule without cracking the insulation. In practice, this means you should never crimp an insulated connector with a non-insulated crimper die, as it can pierce the insulation and expose bare metal (a safety hazard). The reverse (crimping a non-insulated connector with an insulated-type crimper) isn’t as destructive, but it often won’t form as tight a bond. Proper wire crimping tools will be labeled for each type – for instance, some hand crimpers have separate markings or slots for “INS” (insulated) and “NON” (non-insulated). The shape and size of the crimp result are deliberately different for insulated vs. uninsulated terminals to ensure a secure crimp without damage.
Another difference is the possibility of double crimping on certain insulated terminals. Many nylon-insulated connectors allow you to crimp twice – once on the bare wire and a second time on the insulated part of the wire – to add strain relief. This two-stage crimp improves pull strength and vibration resistance. Non-insulated terminals, by contrast, typically get a single crimp on the barrel (though in some open-barrel designs, one set of “wings” grabs the conductor and another set grabs the insulation as strain relief in one motion). In summary, crimping wires with insulated terminals requires a gentler, controlled compression around the metal insert (often using color-coded dies), whereas crimping with non-insulated terminals often uses a more aggressive indent to cold-form the metal. Using the right crimping tool for each ensures you get a solid connection without compromising the connector.
Read more: Cable crimping tool. Everything You Need to Know
Prep Work — Wire Size, Strip Length, and Fit
No matter which type of terminal you crimp, proper preparation is key. Before you even pick up your wire crimping tools, take a moment to prep the wire and terminal:
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Match the Wire Gauge to the Terminal: Always use a terminal size that matches your wire’s gauge. Insulated terminals make this easy with standardized color codes – red for 22–16 AWG, blue for 16–14 AWG, and yellow for 12–10 AWG. For example, a blue insulated spade connector is made for a 16 or 14 gauge wire. Using the correct size ensures the wire fills the crimp barrel properly. A mis-matched size can lead to a loose crimp (too small wire in a large barrel) or an over-crimp that cuts strands (wire too big for the connector). With non-insulated crimp connectors, check the product specs or labeling for the supported AWG range, since there’s no color plastic to signal the size. The goal is a snug fit between wire and barrel.
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Strip the Right Length of Insulation: Using a wire stripper, remove just enough insulation so that the bare wire fits fully into the terminal barrel. Typically about 1/4 inch (6 mm) of bare wire is needed for small terminals (up to ~1/2 inch for larger gauges). Do not strip too much – you don’t want excess bare copper sticking out past the connector, which could cause shorts. Conversely, stripping too little means the insulation might get caught under the crimp and the wire won’t seat fully. A good rule of thumb is that the stripped wire should be just long enough that when inserted, no bare conductor is visible and the wire’s own insulation is right up against the back end of the terminal barrel. Pro tip: for open-barrel (uninsulated) terminals that have separate tabs for wire and insulation, strip only the length of the inner conductor crimp area – the remaining insulation will sit under the second crimp wings.
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Ensure a Clean Fit Before Crimping: After stripping, insert the wire into the terminal before crimping to check the fit. All the bare strands should go neatly inside the barrel – none should splay out. The wire should feel snug, with little to no gap. If it’s a non-insulated terminal, you can visually confirm that the wire fills the barrel and reaches the end. If it’s insulated, make sure the wire goes in until it bottoms out (many insulated connectors have a metal stop inside). This is also a good time to orient any seam on the terminal correctly (for crimpers with indent dies: typically place the barrel’s seam opposite the indentor, so the solid side gets the force). Finally, position the terminal in the crimping tool’s appropriate slot before squeezing. For insulated terminals, use the color-coded die that matches (e.g. red, blue, or yellow) and align the tool so its jaw will press on the metal barrel beneath the insulation. For non-insulated, pick the die opening that best matches the barrel size. Taking these moments to double-check size, strip, and fit will make the actual crimping step go smoothly and ensure a solid crimp on the first try.
Product Mapping
When you have the right terminals picked out, you also need the right wire crimping tools to execute the job. Haisstronica offers quality crimpers tailored for each terminal type, ensuring you get factory-like crimps at home:
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For Insulated Terminals: Check out Haisstronica’s Crimping Tool for Insulated Electrical Wire Connectors (AWG 22–10) – a ratcheting insulated wire crimper designed for red, blue, and yellow insulated terminals (vinyl, nylon, heat shrink). This insulated crimping tool features color-coded jaws (as shown below) that correspond to wire sizes, taking the guesswork out of crimp selection. The ratchet mechanism ensures consistent pressure for a proper crimp without crushing the insulation. The tool’s indent is engineered not to pierce or damage the plastic shell during crimping, so you get a tight crimp on the wire conductor while the insulation remains intact. If you frequently crimp insulated connectors, this tool speeds up the process and produces reliable, uniform crimps every time. (Product link: Crimping Tool for Insulated Electrical Wire Connectors.
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For Non-Insulated Terminals (Open Barrel): Haisstronica also offers a dedicated Crimping Tool for Non-Insulated Open Barrel Terminals & Receptacles. This tool is ideal for the kinds of non-insulated connectors often used in automotive and electronics (such as open-barrel spade terminals, ignition coil terminals, or relay/fuse box pins). Its professional-grade jaws are designed to crimp a wire onto these terminals in one smooth action – curling the terminal’s tabs tightly around the wire and insulation. The crimp profile is wider and toothed, which firmly grasps the wire without cutting it. Like our insulated tool, it’s a ratcheting design with an adjustable compression wheel, meaning you get a consistent crimp every time and you won’t under- or over-crimp. Each crimp cavity is clearly marked for the supported wire gauges (spanning approx. 20–10 AWG), so it’s straightforward to select the right size. If you need to crimp non-insulated terminals, especially open-barrel types, this crimper will give you secure, OEM-quality crimps. (Product link: Crimping Tool for Non-Insulated Open Barrel Terminals .)
Read more: Cable crimping tool. Everything You Need to Know
Conclusion
In summary, choosing between insulated and non-insulated terminals comes down to the application’s safety and durability requirements – and each type needs to be crimped with the appropriate technique. Use insulated crimp terminals (with the right wire crimping tools designed for them) in any scenario where you need the added protection against shorts, moisture, or vibration. Use non-insulated crimp connectors only in controlled environments or when you plan to insulate them later, and be sure to crimp them with a tool that won’t damage the bare terminal. By matching your terminal type to the job and following proper crimping prep (correct wire size, strip length, and using the correct die), you’ll create rock-solid electrical connections every time. Investing in quality wire crimpers – one for insulated terminals and one for non-insulated – is wise for anyone who frequently works with wiring, as it ensures each crimp is gas-tight, strong, and safe. With the guidelines above, you can confidently crimp wires like a pro, whether you’re wiring up an automotive harness with non-insulated lugs or tidying up a home project with insulated connectors. Happy crimping!
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