Stripping outer sheath of 5 core cable back by 20mm...then stripping internal wires by 3mm?

[Flyback]

Hi,
Please help with advice on how to best strip 5 core cable, and then strip each wire internal to the cable?

Today, I had a practical interview involving stripping the outer sheath of a 1 metre length of 5 core cable back by 20mm. Then, each of the 5 internal strands had to be stripped back by 3mm.

The 5 core cable was Lapp Kabel P/N 7038862.
This is farnell part number 1852363, as follows…

https://www.farnell.com/datasheets/...MI0JSpv6Lr6QIVt4BQBh3COAGOEAAYASAAEgIdYPD_BwE

Stripping back the outer sheath

I managed to eventually do the job by using side cutters to strip back the outer sheath.
However, this was extremely difficult and very time consuming as the outer sheath of the 5 core cable was extremely tough.
And as you know, you can’t be too heavy handed with the side cutters or else you are in danger of ‘knicking’ one of the internal wires’ insulation.
I had to discard four cables because I ‘knicked’ one of the internal wire’s insulation in each case.

..On another few cable lengths, I had to discard them because after putting a serrated cut round the circumference of the outer sheath, (20mm from the end), I was repeatedly yanking at the end of the outer sheath in order to try and break the (20mm section of) outer sheath at this serrated cut….(i was trying like this because it seemed to avoid the danger of ‘knicking’ the internal wires’ insulation)……however, this technique resulted in all 5 inner wires gradually “spewing” out of the other end of the cable….meaning the cable had to be discarded in each case.

Anyway, what is “the best way” to strip back 20mm (say) of the outer sheath of this cable without ‘knicking’ the internal wires’ insulation?

***…***…***…***…***…***…***…***…***…***…***…***…

Stripping back the internal wires insulation by 3mm

I was given a wire stripper as follows to do this job…RS 540-1492
**broken link removed**

…however, this covers wire sizes of 10AWG to 20AWG, so I don’t know how this could have been helpful, since the internal 5 wires are all stranded wires and of AWG24 according to the Farnell page (having said that, i thought it was impossible to describe a stranded wire by an AWG number?...google says stranded wire should by described by notation such as “7/0.2mm” and not by an AWG number)

From the datasheet, (above) its not possible to ascertain what AWG of wire stripper would be needed to strip these internal wires…would you agree?

Anyway, in the end, I stripped the inner wires with an adjustable gauge wire stripper as follows…
https://www.lawson-his.co.uk/stanley-stht0-75068-controlgriptm-wire-strippers-150mm-sta075068

..however, this adjustable wire stripper wasn’t that sharp, so some of the wires ended up with the outer sheath kind of getting yanked and stretched off, leaving a very “unclean” stripped end.

What is the best way to strip such internal wires? Note that the 5 core cable datasheet (above) doesn’t give a wire size from which a wire stripper can be selected for this?

 

[throbscottle]

Personally, I would score the cable outer with a sharp knife, so not cutting right down to the wires inside, around where it is to be stripped back to, then try to get it to split around the score by bending the cable at that point, and possibly get my thumbnail in to pull it apart, and it should slide off (since the cable is specified to strip easily). If it won't split, I try to score it a bit more, very carefully whilst bending it, If it still won't split, I would carefully score along the wire to the end, cutting right through the sheath for the last few mm. This last little bit is where you can start to split open the long score and pull the wires out sideways. When you have enough to get hold of you can just pull it sideways against the wires inside and it'll rip right off.

I don't understand the problem you had using the stripping tool you were provided with as the tool states 10-20AWG (ie, 2.6mm to 0.8mm and the datasheet for the cable gives core diameters of 1.2mm or 1.5mm, so you should have absolutely no trouble with this. As long as the tool will cut into the insulation without going all the way to the conductor, the exact size doesn't matter. Hold the end of the wire up to the hole in the stripper and look through the hole to see what size you need to use.

 

[Flyback]

Thanks, the "10-20AWG" stripping tool actually was too big to actually strip the internal wires...even at the "smallest hole", it wasnt actually cutting into the insulation.

 

[Flyback]

Come to think of it…….there were 5 internal wires, and one kind of white “plastic strand thing” running alongside the wires..…I wouldn’t mind betting that this “plastic strand thing” was for ragging and ripping the outer sheath in the way you kind of describe?

 

[throbscottle]

Maybe. I come across a lot of old equipment cables (I strip them for hook-up wire) with a thread inside. I think it's for reinforcement but I've used it in the way you describe. The trouble is the wires normally have some twist to them so it ends up going awry if you try to strip a long way.

 

[rjenkinsgb]

To remove a piece of outer insulation at the end of a cable, "scrape" a groove around it with sidecutters then bend it sharply at the scrape - the jacket should just split. If not, scrape it again while holding it bent until it does.
Then changing the angle of the bend to move the stretched area around the cable should spit it the rest of the way around.

It takes practice and experience with different cable types to get used to the depth of groove needed.

Having cutters with good sharp tips is essential - I always use small flush-cut types, around 4" / 100mm long. The large sidecutters in typical electricians kits are totally useless for this type of work.

You can also get dedicated tools for doing that - eg. this style has a rotatable blade that can be set to cut around the sheath or along it:

https://cpc.farnell.com/rotax/00600/rotax-29-rotary-stripping-tool/dp/TL01667

I almost always just use sidecutters for stripping small wires as well; using flush-cut types with the flat surface of the jaw facing towards the end of the wire makes it quite easy and very quick. Bevelled jaw types are not so good as the bevel tries to ride up the insulation rather than digging in and gripping it.

For large power cable cores, the same scrape-a-groove-then-bend-it method as for multicore cable jackets works fine.

I do use wire strippers for some types, especially if there is no way to hold enough cable to pull against or when I'm building panels and doing hundreds of wire ends. The only type I have found that are reliable for different sizes are the self-adjusting ones with flexible jaws, such as these:

RS PRO Automatic Wire Stripper, 24 AWG Min, 10AWG Max, 197 mm Overall | RS

uk.rs-online.com

The stripper jaws in those are made of dozens of separate laminations, with a rubber backing. They can shape to the wire.
The older type with a metal outer body was even better as they had fine setting adjustments, but they are not made any more..
These do occasionally tear a strand from small multistrand wires.

 

[rjenkinsgb]

Re. the "pull cord" for stripping - if a cable has that, it is directly under the outer insulation.
Telephone cables and burglar alarm cables often have that.

The dummy core at the centre of some multi-core cable is either an aid for manufacturing with smaller types, or sometimes a high-strength "strainer", something to take any tension the cable is subjected to so the copper cores are not stressed.
Some types I work with have something like a 6mm polypropylene rope at the centre that can be used as end anchors in moving machinery.

 

[alec_t]

Here's what I use for cutting the outer sheath :

It's a cheapo screwdriver blade with the end ground off at an angle and sharpened. The brass terminal from a chocolate-block connector makes an adjustable depth-stop.

 

[Mickster]

Personally, I would score the cable outer with a sharp knife, so not cutting right down to the wires inside, around where it is to be stripped back to, then try to get it to split around the score by bending the cable at that point, and possibly get my thumbnail in to pull it apart, and it should slide off (since the cable is specified to strip easily). If it won't split, I try to score it a bit more, very carefully whilst bending it, If it still won't split, I would carefully score along the wire to the end, cutting right through the sheath for the last few mm. This last little bit is where you can start to split open the long score and pull the wires out sideways. When you have enough to get hold of you can just pull it sideways against the wires inside and it'll rip right off.

This is the method that I use, and would like to add that the sharper the blade, the better.
Once the score mark has been made and the cable bent to widen the score mark, the sharp blade makes it easier to help the sheath split, by only using very light pressure, instead of having to push hard on a dull blade.

 

[gophert]

If one is a hack or has ham-hands, there are dozens of "Cable Slitters" That are rotary, or racheting or lateral undercutting and some that have replaceable razor blades of preset depth for multiple wire sizes on a single tool. There was likely one in the box full of tools they provided, you just didn't know what it was or how to use it.

I, on the other hand, am not ham-handed and I have the craftsmanship and skill to do it with a pocket knife, razor blade or, for smaller cables, my teeth. Note: PVC jackets taste weird because of the organo-tin catalysts.

 

[alec_t]

PVC jackets taste weird because of the oregano-tin catalysts.

Didn't realise you could get herbal-flavoured cables .