HOW TO – Cut insulation off multi-core wire

HOW TO – Cut insulation off multi-core wire – (m4v)… have a handy tip on doing this too? Post it up in the comments!

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  1. That’s a neat trick. I cut a fair bit of multicore cable from time to time, and I’ve never seen that done before. No more inch-long fragments with damaged inner insulation / conductors all over the workbench 🙂

    I suspect ribbon cable will continue to be a problem, however…

  2. I’ve simply scored the outer insulation to where I do not even come close to breaking all the way through it to risk damaging the insulation of the inner wires. I then hold onto the cable behind my score mark and grip the part of the insulation that needs to be pulled off with a pair of pliers and pull it off. Usually the simple score mark is enough to cause the insulation to break the rest of the way through when you pull with the pliers. This way I am always assured I don’t knick the inner cable’s insulation and don’t need to bend the inner wires so sharply.

  3. Hi, if you cut a ring into the outer insulation before you bend the wire, the insulation will crack open just as you bend it (when cut properly)…
    That’s the way I do it, and the danger of cutting into a core is in my opinion much less imminent.
    happy hacking, tobi

  4. My old electronics lecturer would kill you for doing it that way! Far too much chance of accidentally nicking the inner insulation, no matter how careful you are. This is especially dangerous with mains electricity.

    The “correct” method is to make a nick in the outer insulation right at the end, going down the cable (about 10mm should be fine). Then grab some of that string / nylon inside the cable and pull it through the nick you just made, and then down the cable to extend the cut down to wherever you need. Finally separate the outer insulation from the bundle of wires, and cut off the outer insulation.

    Maybe I should make a video?

  5. jon, if you’re lucky, theres nylon or string inside you can get to easily. sometimes there isn’t.. this one happened to but ive worked with ones that dont. if you are careful you dont cut through the insulation, you really only make a nick on the outside like the other commenters’ do. it takes a little skill, and then examining the inner wires carefully.
    For mains cables, you dont need to do this at all because the outer plastic is loose enough.

    however, more videos are always suggested, especially if you’re convinced your technique is superior 🙂

  6. I’ve used this technique myself and it really does work very well. An important point, which isn’t mentioned explicitly in the video (although I can see it’s being done), is that the razor blade is pressed down, but not dragged across the surface of the insulation. This is what makes it much less likely to nick the inner insulation. It’s really the tension from the bend that’s doing the work here and you can often feel when the razor has made it through the outer insulation due to a very slight “snap” when the two halves finally separate completely. Stop pressing on the razor as soon as you feel that.

  7. mike, thats right! the video may not be completely clear but im actually rotating/rocking the blade AROUND the cable.

  8. William Reading

    Doesn’t this put undue stress on the conductors on the inside? You might not nick the insulation, but you might mess up things that you can’t see as easily.

  9. william, for stranded core, no.

  10. what about taking your much touted xcelite stamped steel dykes and cut down the insulation parallel to the conductors? The jaws are thin enough to cut down without biting the conductor insulation.

    I don’t recall the last piece jacketed cable that didn’t have a ripper built in.

    You should demo that, I suspect fewer people know that you can rip the fine silken filament through the outer jacket to expose the inner conductors.

    In outdoor applications (in humid S. Florida)nicking the inner conductor would guarantee you a quick green corrosion failure. Especially phone wires!

    I promised my techs that I’d fire the first one I saw doing it the way you are doing it!

  11. scienkopic & jon, what company do you work for/what school did you attend? i think its interesting that one would be killed or fired for stripping insulation this way.

    However, it sounds like both of you know the best way to do this, so perhaps you can make a video? a short one would be fine, just a minute. we’ll post it up here! Please please please! 🙂

    i was shown this technique when i had to strip 7conductor 32awg wire the entire bundle was <3mm thick diameter. you couldn't fit a -needle- down it much less xcelites (i do use xcelites for cutting down larger cable. the jacket was so thin, one couldnt even pull a razor lengthwise without slicing the inner conductors. the wires were short as well, about 4" long, so not sure that the nylon inside would not just 'pull out' (i vaguely remember trying and having it all come out)

    When you do your video, be sure to show how to cope with short wires like that, they're common in projects and I'd love to learn the proper way to do it


  12. i’ve used almost this exact same method for close to 30 years. difference is i use an xacto #1 knife. there is no telling how many 8-cond serial cables i built in pre-pc/vax days. never any problems. the one tool i also keep handy is a set of sharp pointed plato’s to get the little pieces the knife might miss.

  13. Hi I think the best way of stripping the wire is your own way. The best way is with practice. I have stripped cables now for quite a while now and in the beginning it was such a pain finding that you nicked the cores inside, but after a while you learn the right pressure to apply to your blade. My method is exactly like Tobi mentioned above, but like I said it all comes withtime and practice.

  14. I’ve found that the safest and simplest way for me is to use a nail-clippers. Just lightly ‘nip’ the insulation a few times as you rotate the clippers. Quite a lot of control and no need to have razor blades.

  15. I own my company. or it owns me.
    I make the rules.
    I speak of firing employees because much of our work is wet location or underground. I’ve learned the hard way that razoring insulation perpendicular to the inner strands will always lead to conductor failure. ($$$$)
    In some cases: THHN wire, the outer skin of the wire insulation is what gives it the appropriate rating (oil, water, etc) Cutting that outer sheath compromises the inner insulation which is not rated.

    I don’t work with much smaller than 26AWG and that typically is solid wire.
    And the outer jacket is UHMW or PE.

    I’ve done it your way and there’s nothing wrong with it if you’re careful and the wiring isn’t going to get wet.

  16. scienkoptic said: I suspect fewer people know that you can rip the fine silken filament through the outer jacket to expose the inner conductors.

    That’s the truth. I only figured it out recently, while stripping 20′ of CAT-3 cable. The first 8′ was slow, then I figured out what the nylon string was for, and the last 12′ was instantaneous.

  17. I often work as a wiring tech for recording studios and television facilities around the country, and we strip tons of expensive multi conductor cable.

    The method you demonstrate is the only method that has been considered ‘acceptable’ by the various foremen of the jobs I’ve worked on. (of course there are exceptions depending on the cable) A fancy stripper tool is generally not acceptable to use on the outermost jacket.

    An important variable to consider is the manufacturer of the cable… Some manufacturers use a stiffer type of plastic for the outer jacket that will break at the score point more easily than others. Either way, the most important thing is to use caution and be mindful of how deep you score the jacket with your blade. The goal is to score it then break it, not cut all the way through.

  18. Ken:

    I’ve spent many hours ripping out stuff that was installed in the ‘acceptable’ method.

    The best method is one that does not damage the insulation and expose conductor.

    I don’t care how careful you are, you *will* cut through the insulation when using a razor blade. Maybe not always, but every once in a while you will. Most jacketed wire I work with is irregular. There are high and low spots.

    I’m not terribly good at laying out circuit boards or designing circuits or programming Arduinos, but I’ve stipped many thousands of feet of wire – a few inches at a time.

  19. Ladyada:

    I’ll work on that.
    I’ve got to figure out vimeo again….

  20. Yup,
    I’m with Jon.
    This here’s a bad idea. There are an endless number of things one might do with practice under ideal conditions; which are, in the real world, prone to risks. No question, if results doesn’t matter, strip wires anyway you like. But if it matters, one doesn’t introduce wires to a razor. Just attack the wire from the cut end with a pair of diagonals, and keep slicing until you’ve unzipped enough cable; then separate the outer insulation from the wires, and cut them separately – zero risk of a nick, zero need to “check closely”.

  21. I think it is interesting that each technique has its own problems

    razor: inexperience can nick the conductor
    ideal-t: has to be the right size hole or unexperienced can nick conductor.
    round cable cutter: slow, needs to be adjusted for cable
    cutting down side: sometimes no room, can cut wires if not careful
    pull, cut & peel: good for old telco wire only

    Could it be that there are many styles and each technique is good for certain situations?

    As I said in the video (you did watch it, right? 🙂 ) the proper tool to use is an automatic stripper or similar. Using a razor is when you’re a broke student, hobbyists, etc. If you work for a co. and your job requires stripping wires, make sure your boss gets you the best tool possible.

  22. The technique you presented works, but it does stress the inner conductors if you flex them too far. I prefer to nick the insulation before bending and then bending the wire to finish the job. It’s kinda backwards to the way you’ve done in in the video. It takes some experience to get it right but once you have the experience, it’s really easy to do and you don’t generally bend the wires nearly as far.

  23. There’s a little plastic gizmo you can by at telco suppliers that makes this quick and easy. It looks like a single “scissor”–one ring to stick your finger in, and a single, split straight piece with an embedded (and depth controlled) blade inside the split.

    You just clip it over the wire, stick your finger in the ring, and whirl it around the cable. Wired up my old house with four runs of CAT5 to every room using one of these.

    Looks just like this one, but I think I only paid a buck or two for one at Graybar.

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