IWISS SN-025: Another “DuPont” crimp tool lands

Following on from my recent review of the Preciva PR-3254 crimp tool, I hit up eBay and Amazon to see if any other such tools may have surfaced lately. I found one:


We have a new tool (Amazon UK link), which is also apparently specifically designed for these contacts. At the time I wrote this article, the SN-025 is not (yet) listed on IWISS’s website? IWISS now have a product page for this tool.

A little bit of context

Left: The jaw of a typical budget tool. Right: SN-025

SN-025 is a particularly unusual crimp tool because it has ‘O’ shaped insulation crimpers. Some contacts (for example “DuPont” type) require a tool like this for correct crimping however historically almost no generic hand tools with this type of die had been available.

In the decades since imitation DuPont Mini-PV connectors first surfaced, hobbyists instead had to resort to mutilating contacts in unsuitable tools like the one above on the left. Only those in possession of either the DuPont-designed hand tool (extremely expensive) or the appropriate automated applicator had been able to crimp them correctly.

Two contacts apparently crimped with the IWISS SN-025. A “DuPont” contact, and, err, what’s that other one? Recognise it? please drop a comment.

The above graphic is provided by the Amazon seller, specifically pointing out that it wraps the insulation around the wire. It’s almost as-if they’ve been reading my crimp connectors page

While this is being sold as a “DuPont” crimp tool, it appears it is predominantly designed for Superseal contacts. Not something I’ve ever used myself, but no doubt commonly used in the automotive space.

  • AWG 28 for “DuPont” contacts
  • AWG 20 for Superseal contacts
  • AWG 18 for Superseal contacts

The AWG 28 die

DuPont HT-95. The gold standard which I’ll be comparing against. Edit: Since I wrote the page, I have obtained another tool, which is even better than the above for crimping “DuPont” clone type contacts.

Let’s put some “DuPont” contacts in there and see what we end up with:

Of course SN-025 wasn’t going anywhere near the HT-95’s crown as ultimate “DuPont” crimp tool. (Since writing this article I have come across a slightly better tool for these contacts). It did do marginally better than the Preciva PR-3254 I reviewed previously.

The SN-025 not having an AWG 24 die, it over-crimped the insulation as we would expect, and the wire part isn’t crimped anywhere near as tight as it is supposed to be – typical for Chinese tools.

If we were to cut open the wire parts of the DuPont vs IWISS crimps, we would find something like this. For the SN-025, likely a lot worse. Source: TE Connectivity

The other two dies?

The marketing image typically attached to this tool features a mystery contact crimped onto AWG 22 wire. Whatever it is, I don’t have one, but it doesn’t matter because I’m only looking at the crimps. Let’s put some AWG 22 wire and a similar sized contact in the AWG 20 die and see if we can re-create it:

Nope. The insulation crimp is far too loose, not gripping at all, so that picture is hogwash. Let’s see what else we could potentially use those dies for…

I went through my crimp tool cupboard to see if I had any others like this. Of the, err, considerable number (I’ve lost count) of manufacturer original tools in my collection, just seven have an ‘O’ type insulation crimp. Only two of those were in this wire size range:

Top: TE Multimate crimp tool. Bottom: TE Economical Interconnect crimp tool

TE Multimate

An interesting type to compare against because Multimate contacts look quite similar to the one pictured in the image the tool is sold with. Given how esoteric these are, no point in going any further into that.

Economical Interconnect

A common type stretching to AWG 20 wire size, which has an ‘O’ crimp. More about these here.

KK .396 (?)

Lost in translation? The range of contacts apparently crimped by this tool. Including a rare and expensive gold plated Mini-PV male. Not something I’d expect the typical purchaser of this tool to be using.

In addition to the “DuPont” types, Molex KK .396 (.156″) is offered as a supported contact type. Not something the average hobbyist is going to be reaching for. I’ve got the manufacturer original tool for these, it’s not quite an ‘O’ type crimp, but let’s give it a shot anyway:

Mini-Fit Jr (?)

The die in the manufacturer original tool is quite similar to the KK .396 tool, so we’ll look at these too.

Certainly not one for E.I. It was OK on the wire part but it didn’t touch the insulation crimp.

For KK .396. Pretty good! the insulation part is a smidgen too loose on AWG18 wire, even when crimped in the AWG 20 die (forget it for AWG 20 wire). The results do not match the marketing image, I can only assume that was done by a different tool. Or, perhaps, the marketing image is depicting a smaller KK .254 contact?

Last but not least, the results for Molex Mini-Fit Jr looked quite good, so I’ve taken a closer look:

AWG 18 wire crimped by 3 tools. On the left a typical result of a budget tool, with the insulation deeply pierced due to the very long tabs on these contacts.

For the SN-025 crimp on the right: It takes a bit of practice, and the lack of a bell mouth has cut the wire a little, but otherwise the SN-025 has yielded a result very similar result to the Molex 63819-0900, correctly and cleanly wrapping the insulation support. The SN-025 doesn’t have the needed asymmetry in the insulation crimper to allow the tabs to easily fold over each other, but it they seem to most of the time when I tried it.


While I have shown it used for E.I, KK.396 and Mini-Fit Jr, this is purely experimentation, and I would emphasise that the manufacturer does not recommend this tool for these connector types.

For “DuPont” contacts, which are officially recommended, it does significantly better than other tools generally used by hobbyists, however as always my recommendation is that this tool (and any other tool in this price bracket) should only be used for applications in the “fun” category, specifically the kind of fun that doesn’t involve someone losing an eye when it goes wrong.

I have detailed a number of other tools to consider on this page.

Posted in Crimp tools and connectors

9 thoughts on “IWISS SN-025: Another “DuPont” crimp tool lands

    1. Cheers for spotting that. Looks like speculation about the spec/purposes weren’t too far off. Surprised to see “DuPont” officially listed there…

      1. Do you think this tool is the best non official tool for KK .254 terminals also?

        Looking for a tool to crimp these connectors but don’t like how the sn 28b does it as it does not wrap the wings around the insulation like the official tool does so wondering if this would whilst still giving a good crimp in the wire part for 22awg wire.

        Yet again your write ups are helping me so much!!!

        1. The SN-025 crimps the insulation tabs as per the original tool, however the conductor crimp is looser. Definitely better than the SN-28B, however the Hozan P707 is better because it also crimps the insulation part perfectly, and can achieve higher force on the conductor crimp.

  1. I have been messing around with the sn-025 and I have found that if you “pre-crimp” the molex mini fit Jr contacts with 3 clicks of the ratchet, release it the rachet mechanism. Then put the wire into the contact and put the contact and wire back into the sn-025 I get a great crimp each and every time. Not once has this little work around gave me a bad crimp. I am debating whether to actually switch from the sn-28b to the sn-025 for mini fit Jr contacts!

    1. That’s cool to hear!
      Which wire gauge did you use this on? I’m debating on buying this for my little “iwiss collection” 😀
      Merry Christmas to you and Matt!

  2. What are the differences between the HT-94 and HT-95/HT-0094 and HT-0095?

    Do both have the BergStik pins inside to hold on to your Mini-PV connector/terminal while you insert the wire? Do either have a wall like Z20-320 which you can feel when the conductors have hit the stop/the wall?

    Thanks in advance.

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