the channel why do i continue to train learners to use an electrician's knife
when stripping cables and i haven't converted over to something like this combination wire strippers
especially when we're stripping things like twin and cpc often called twin and earth cables however
i would like to suggest i've also got videos on the channel where i use the electrician's knife
when working with flex steel or armored and sy flex when terminating it but in this video
we're going to address the reason behind me using electrician's knife when stripping twin and cpc
cables so if i bring the camera in let's have a look and see if i can justify the use of this tool
let's start with the most obvious one then it's considerably cheaper to have a fixed blade
electrician's knife in our tool kits at Tresham college than it is to have a set of flat
twin and cpc cable strippers in there because they are considerably dearer than the actual
electrician's knife however i'm sure you're saying now why don't we have three or four of
these on a shadow board and learners can share them at the very start of the course we spent
about 12 weeks working on twin and cpc or twin and earth cables and that means that you've got
20 learners in the workshop probably all waiting for these to come round why would that be well
let's just strip a piece back this is a bit of 2.5 so we place them through the center of the body
simply pull and you can see already the mechanical protection has been removed if we go in again
we can actually strip back the insulation around the conductors and you can see already
i'd imagine i'm really sold you on these how easy they are to work with so that's great that's a
real real advantage that they are quick there are some disadvantages they only go up to 2.5
millimeters squared and we work with four and six mm throughout the course as well which these are
no good for and also the fact that we can't get them into a box very well so let's see that so if
i take myself a box and i've got myself a piece of uh three core cable here if i slide it into
the box itself to about the appropriate position obviously we would have clipped this down etcetera
and i just make a mark against where i'd like it to be about 15 mm in let's see if we can strip
this three core using these twin and cpc or twin earth strippers let's wind it through the body
and then all of a sudden there i'm stuck i can't get it in any further than that if i pull that
i'll just pull it back out and see the line these are a bit difficult to pull off there we go so
you can see that much of the outside mechanical protection would still be present inside the
box where i don't want to see it that's because these strippers will not get infer enough to strip
it if i was to use my electrician's knife i've seen it on the channel many times before
you can already see that i can get my knife right down into the position
where i need it in order that i can strip that cable so and then fold it over and do the back
that's why we use the knife for that things so this here doesn't get in fair enough and stops
at 2.5 this will let's strip a piece of cable using my knife just to remind you of the technique
so gently score not saw around the actual mechanical protection itself
then i get my learners just to snip down the middle of the cable
like so and we leave our cpc in the middle and what you're thinking now is why don't you teach
people just to grab hold of the cpc Gary and pull it down to the score area you've got down here
the reason being is we use lengths often less than half a meter long very early on and what i've had
before is learners actually not pull up on these but actually pull away and they've pulled the cpc
out of the cable itself and they've brought the cpc to me and said uh what do i do now Gary well
you unclip your cable and you replace it back onto the board you know get a lot of fuss and uh for
some moaning at that stage so we come up with a technique of actually holding our live conductors
and rolling it out across our knuckles until we get down to the area in which we need to pull
the actual mechanical protection off so that meant that we didn't accidentally
pull the cpc out now i can't suggest in the real world that i've ever not pulled against the cpc
down to my area which i've scored in order that i can actually break away the mechanical protection
so that's why we do that so we gently score around here and that's why i always hold the two
live conductors and leave the cpc alone and don't pull against it next we take our knife and let's
score around here to be fractionally harder now but people have said to me oh you might
you might damage the actual copper so of course it weakens it in that area so let's
it will break i would imagine but let's see how many times i have to wiggle it before it breaks
it'll eventually go it eventually broke at that time but it took a lot of
uh obviously pressure to do so but let's do the same with the combination wire strippers
strip that back take the same pliers and then just get hold of it and then see what happens
this time there you go that one broke as well so again i don't think there's much of a case there
okay i'm trying to get my learners to understand how hard to press with a knife not to damage
in this case the inner insulation around the conductors when removing the mechanical protection
and how hard to press against the actual insulation in order to remove it and then
not damage the copper itself it goes back to that hand-eye coordination
when you're trying to learn those skills remember at college you've got all the time in the world
in which to hone your skills when you're out in industry you're trying to do things fast
and effective people then say well Gary why don't you teach them to use your side cutters so
why don't you take the side cutters and show them this technique just to pull it off okay and again
we've tried that in the past i'll show you what happens when a learner that doesn't know hand-eye
coordination and pressure they go like this they go strip strip strip and then they come
to me and go my conductor's not very long Gary what do i need to do need to take the cable out
and you need to replace it and then obviously start again oh that's going to take a load of
work i've clipped it in place it's smooth it's got a nice bend it's because they haven't yet learnt
obviously the coordination required in order to strip the cables perfect every time let's see if
this one's worked hardened so i don't think it has but again i can eventually get it to break
nope ah and it's broken so again is there a is there a conversation to have about how hard you
press with the knife yes there is is there a conversation about using these wire strippers
they're very good but very limited can we get our students to use side cutters or pliers not early
on because they tend to do that when they're learning to strip them back this only goes up
to 2.5 is what we said so again once we get to 4 and 6 mm they've got to come up with a technique
in order to strip the cables and that would be the technique that we've just looked at so
learning to use the electrician's knife early on and then maybe owning a set of these in the future
is a good way to build in the skills required before going to a tool that makes it a lot easier
the other issue i've got is that i can sharpen these very simply in an electrical workshop i can
sharpen the knives and the students can as well in order that we don't have a blunt instrument
your feedback would be welcome here how long do the blades in here last imagine these are
in a workshop and we've got 12 hours of study in there and that the first 12 weeks everybody's on
twin and cpc cables with the blades in here last how easy are they to find to replace
how easy are they to replace your feedback would be welcome on that so again really good but are
these almost for the occasional stripping of conductors throughout a working day and not to be
put to task every minute of every day for 12 hours a day as we go through a week at college we found
our torque screwdrivers um got destroyed almost because of the amount of times they've been used
you imagine electrician's doing consumer units maybe one a day but his torque screwdriver does
all the terminations in there we've got 20 people all doing the consumer unit all at the same time
our torque screw drivers um failed quite quickly um on the mechanical stress that we put them
under so would these last being in electrical workshops such as Tresham so we use the knife
because we believe it builds hand-eye coordination okay it's cheaper for us to have it in our toolkit
we also do not pull the cpc from our conductor through the center like often they do on site
because we've seen it being pulled out and we also know that we've got to get it into
the right part of the box and this becomes very difficult in order to get it in there
so i'm not trying to justify it i'm just trying to answer that question why do i still persist
with an electrician's knife there are other tools out there and for some of our students
over the years that have struggled with hand tools we have adapted the tools to make it a
safer working environment people were saying to me under the health and safety workout you
can't use that health and safety work act is not a massive document to read and at
no point does it say in there that Gary can't use an electrician's knife in Tresham college
however it does say to use the safest work in practice possible and if we believed it wasn't
safe for a learner to use this style of tool then we would adapt their working practices to suit
i never advocated so let's see what we've got here okay let's go with the three core i've
never had vacated things like using maybe your side cutters and then snipping down the center
getting hold of the cpc this one should be long enough i don't pull it out down to where we are
peeling it away and then obviously using the side cutters again in order that we go
and around here so let's just do the best we can almost all good i've split past it that's nice
getting with side cutters and then come around this side okay and say that is acceptable okay
we're looking for ends i know we did this one and this one here three different methods you
can see that's used the combination wire strippers that's used a knife and that's
used a technique that wouldn't look pretty in a box okay i know we're never going to see it
okay but that doesn't look very good at all and obviously i like my ends to be nice and square
no damage to the inner insulation okay and obviously that pvc there looks a little bit untidy
hopefully i'm again i'm not trying to overly justify everyone to their
own if you've got a better method than i have leave it in the comments below
if there is a better way of teaching this i apologize that i've been using this technique for
18 years we have 10 tools in the threshold toolbox of which the electrician's knife is one of them we
try and build those hand-eye coordination early on for students especially nowadays where maybe
learners come to college and haven't taken their bike apart or their skateboard apart and all the
rest of it and need to work out how to do things uh properly and hand tools are sometimes foreign
to them if it wasn't safe for them to use would adapt their working environment to suit
surely every college in the country would love these and love 20 30 sets of those
so students can use them but again it's limited it only goes up to 2.5 and can't get into a box