Co-axial cable stripping tool and end portion preparation method

A tool for preparing the end portion of a co-axial cable has a blade which may pivot between two limiting positions, in one of which the cutting edge of the blade lies across a cable-receiving opening to a greater extent than in the other of which positions. On inserting a co-axial cable through the opening and rotating the tool around the cable in one sense, the blade is caused to move to one limiting position so effecting one depth of cut, but on rotating the tool in the other sense around the cable, the blade is caused to move to the other limiting position so effecting a different depth of cut. In this way, the different layers of the cable may be severed and removed. In the method, a first cut, for example with the tool described above, is made around the co-axial cable to a depth sufficient partially to sever the insulating layer overlying the cable core: the partially severed portion is twisted around the cable core totally to separate all layers overlying the core; a second cut is made further from the cable end to precisely the same depth as the first cut; and a third, relatively shallow cut is made yet further from the cable end, this time just to sever the outer layer. An axial pull then successfully exposes the cable core, inner insulator and outer conductor.

This invention relates to a tool suitable for preparing the end portion of 
an elongate member having a core and at least three layers therearound, by 
stripping the layers back to expose the core and other layers from the end 
of the member. The invention further relates to a method for preparing the 
end portion of such a member. In particular, but not exclusively, the 
invention relates to a tool specifically intended to assist the 
preparation of the end portion of an electric co-axial cable to permit the 
electrical termination thereof, for example by a jointing technique or by 
the attachment thereto of a co-axial cable connector, and also relates to 
a method specifically intended to prepare such an electric co-axial cable, 
successively to expose the core and overlying layers, from the end of the 
member. 
Though the tool and method of this invention may be used to strip layers 
from multi-layered elongate members other than electric co-axial cables, 
it will in the following be described with specific reference to electric 
co-axial cables. However, it will be appreciated that the tool and method 
does have other applications--for instance, the preparation of end 
portions of fibre optic cables--and the term "co-axial cable" as used 
herein should be construed accordingly. 
A typical electric co-axial cable has three layers around a central 
conducting core--namely, an insulating first layer, a conducting second 
layer and an insulating third layer or outer sheath. Any of these layers 
may be formed as a group of two or more distinct sub-layers--for example, 
the conducting second layer may comprise a first sub-layer of copper foil 
wrapped around the insulating first layer and a second sub-layer of 
braided copper strands laid over the copper foil; and the insulating third 
layer may comprise two or more sub-layers in order to impart to the 
completed cable the required electrical and mechanical properties. The 
invention is of course applicable to such multi-layered cables, and a 
reference hereinafter to any particular layer of a cable is intended to 
apply equally to a group of layers, where such a group serves the function 
of a single layer and so should be removed as a single layer when 
preparing the end portion of the cable. 
The stripping of the end portion of an electric co-axial cable to prepare 
it ready for termination presents considerably greater problems than those 
encountered in preparing a conventional single conductor wire. In a 
manufacturing concern, such problems may be overcome by appropriate 
automated machinery which is both complex and relatively expensive. 
However, for on-site installation of co-axial cables, or for relatively 
small scale users of such cables, the use of automated machinery is not 
appropriate and the preparation of an end portion of a co-axial cable can 
present certain problems. The usual manual method of preparing the end 
portion of a co-axial cable is by using a sharp hand-held knife--and with 
some experience, an operator may prepare the end portion of a co-axial 
cable with complete satisfaction. This action may be assisted with a wire 
stripper, perhaps especially adapted to the cable to be prepared. 
Nevertheless, the preparation of the cable still takes some considerable 
time, and quite often the conductors are accidentally "nicked" by the 
knife being used to remove the insulation. Also, the operator may inflict 
a serious wound on himself, by using an open sharp knife blade to perform 
the actions firstly of removing a relatively long length of outer 
insulation from the co-axial cable, and subsequently removing a shorter 
length of outer conductor and inner insulator. 
It is a primary object of this invention to provide a tool suitable for 
preparing the end portion of an elongate multi-layer member and 
specifically an electric co-axial cable, which tool is very simple to use 
and yet is able reliably and consistently to cut selectively through 
either only an outer layer (e.g. the outer insulating layer of a co-axial 
cable) or more than just the outer layer (e.g. the outer insulating layer, 
the outer conductor and the inner insulating layer of a co-axial cable, 
without also cutting the inner conductor). 
According to a first aspect of this invention, there is provided a tool 
suitable for stripping distinct layers from a multi-layer elongate member, 
which tool comprises a body defining an opening in which may be received 
the member to be stripped, and a cutting blade pivotally mounted with 
respect to the body and movable between the two limiting positions in the 
first of which the cutting edge of the blade projects to a relatively 
large extent into the opening and in the second of which the cutting edge 
projects to a relatively lesser extent into the opening, whereby following 
the location of a multi-layer member in the opening and rotating the tool 
around the member in one sense, the blade is caused to move to one 
limiting position such that the cutting edge substantially severs several 
layers of the member, but on rotating the tool around the member in the 
other sense the cutting blade is caused automatically to move to its other 
limiting position such that the cutting edge severs fewer layers of the 
member. 
The following further description of this invention will refer exclusively 
to electric co-axial cables, though it will be appreciated that many of 
the preferred features are applicable to tools intended for use with other 
elongate multi-layer members. 
When the tool of this invention is to be used with a co-axial cable, it 
must specifically be designed to match the cable configuration--but since 
such cables come in a relatively few number of sizes, this need not 
present a significant disadvantage. The arrangement of the tool is such 
that when it is desired to expose the inner conductor of a co-axial cable, 
the tool is suitably positioned on the cable and is rotated therearound in 
one sense, whereby frictional drag on the blade causes the blade to move 
to its first limiting position so severing all the layers over the core 
conductor though the layer immediately overlying the core may only 
partially be severed, radially. Then the tool is again suitably positioned 
on the cable at the point where the outer conductor is to be exposed, and 
the tool is moved therearound in the opposite sense, so causing the blade 
to move to its other position where the cutting edge severs only the outer 
insulating layer. Stripping of the severed layers may thereafter easily be 
accomplished. 
Configuring the tool to suit a particular cable enables the tool to be used 
successively to expose the core and each overlying layer of the cable even 
though the tool effects only two different depths of cut. This is obtained 
by having the deeper cut only partially severing the insulating first 
layer of the cable, over the core. To do this, a first deep cut is made 
adjacent the end of the cable by rotating the tool around the cable in the 
appropriate sense, whereafter the severed outer layers are rotated around 
the core with respect to the remainder of the cable, so completely 
separating the first layer whilst leaving the core intact. The tool is 
then moved further on the cable and a second deep cut made, but the outer 
layers are not subsequently rotated around the core. Next the tool is 
moved yet further on the cable and a third cut made, but this time by 
rotating the tool in the opposite sense so causing the blade to move to 
its other position and so effecting a shallow cut through the outer layer 
only. Preparation is completed by pulling the tool off the cable whilst 
leaving the blade in the third cut, which action slides the severed layers 
off the end portion of the cable, so successively exposing the conducting 
second layer, the first insulating layer and the conducting core. 
In view of the foregoing, it is a second object of this invention to 
provide a method for the preparation of the end portion of a co-axial 
cable which method can be performed by a simple device but which method 
permits adequate cutting of the layers to enable the removal thereof, 
without risk of damage to the core. 
Accordingly, a second aspect of this invention provides a method for 
preparing the end portion of an elongate member having a core and at least 
three co-axial layers therearound so as successively to expose the core 
and layers from the end of the member, which method comprises: 
(a) effecting a first cut around the member at a position adjacent but 
spaced from the end of the member to a depth sufficient partially to sever 
the layer immediately overlying the core; 
(b) twisting the so-severed layers around the core so as to complete 
separation of the end portion of the layer immediately overlying the core 
from the major portion thereof; 
(c) effecting a second cut around the member at a position spaced further 
from the end of the member than the first cut and to the same depth as was 
effected the first cut; 
(d) effecting a third cut around the member at a position spaced further 
from the end of the member than the second cut but to a lesser depth 
sufficient at least partially to sever the third layer overlying the 
second layer but not to sever that second layer; 
(e) applying axially of the member and in the direction of the end thereof 
a force to the severed portion of the third layer at or immediately 
adjacent the third cut thereby to strip from the member successively from 
the third cut the third layer, the second layer and the first layer, so 
leaving an exposed length of the core at the end of the member. 
In performing the method of this invention, it will be appreciated that 
though three cuts are made around the cable, two cuts (the first and 
second cuts) are made to the same depth, and so a tool designed to perform 
this method may be much simplified in that it has to be capable of 
effecting only two different depths of cut. Moreover, by only partially 
severing the first layer with both the first and second cuts, there is no 
risk of damage to the central core by the cutting blade, and so cables 
manufactured with even relatively poor concentric tolerances can 
successfully be prepared by this method. 
Preferably, the cutting blade of the tool of this invention is pivotally 
mounted on a carrier itself slidably mounted with respect to the body, 
whereby the blade may be moved clear of the opening by sliding movement of 
the carrier so facilitating the insertion of a cable into the opening. For 
such an arrangement, the opening may be in the form of a through-bore, in 
which the cable may be received. Advantageously, a resilient bias is 
provided between the carrier and body, to urge the blade towards the 
opening. This enables the blade progressively to penetrate the cable to 
the required depth as the tool is rotated around the cable. 
The blade conveniently has a mounting hole by means of which the blade is 
pivoted to a pin provided on the tool body (or carrier, if provided). The 
blade may then have a second hole, preferably in the form of an elongate 
slot, through which a second pin passes with clearance, the pivoting 
movement of the blade being limited by interengagement of one or the other 
sides of the second hole with the second pin. 
Preferably the tool includes guide means assisting the positioning of the 
tool with respect to a cable. Such guide means may comprise a projection 
from the tool body adjacent the opening and having graduations or other 
indexes for alignment with the cable end or an annular cut already formed 
therein. 
In an alternative form of the tool, the cutting blade may be set relative 
to the body at a slight angle to a strict radial plane of a cable located 
in the opening, whereby rotation of the tool around the co-axial cable in 
the sense causing the blade to effect a shallow cut causes the body to be 
threaded along the cable, whilst at the same time at least partially 
severing the outer insulating layer. The severed outer layer thus is in 
the form of a helicoid, at the completion of the severing operation, and 
may with great facility be removed from the cable simply by pulling the 
free end portion of the helicoid in an axial direction. Rotation of the 
tool in the other sense around the cable, to sever all of the layers 
except the inner core, should not cause axial movement of the tool along 
the length of the cable, in view of the considerably great depth of 
penetration of the cutting blade. 
The body of the tool may suitably be profiled to lend itself to the ready 
rotation thereof around a co-axial cable. For example, the body or the 
blade carrier (if provided) may include a rounded finger hole. In an 
alternative arrangement, the blade may be pivoted directly to the body and 
be appropriately profiled to permit the application of a force thereto to 
drive the blade--and hence the body--around the co-axial cable to be 
prepared. In such a case the same severing action can be obtained, because 
the body will tend to trail behind the rotation of the blade, owing to the 
friction between the body and the cable, so following the rotation of the 
blade in whichever sense a rotative force is given to the blade. 
The method of this invention as described above stems from the realisation 
that the first layer over the core, when partially severed by a radial cut 
therearound, can thereafter be completely separated from the major part of 
that layer by twisting the partially-severed portion about the core, so 
permitting the subsequent removal of that layer, or can be left to remain 
connected to the major part of that layer, if subjected just to an axial 
force through the overlying layers. The depth of cut required to achieve 
reliable separation on twisting, but sufficient strength to hold the 
partially-severed portion to the major part when axial force alone is 
applied, depends upon the particular materials of the cable as well as the 
dimensions of the cable, but tests have shown the cut should sever the 
first layer to a depth in the range of from 20% to 50% of the first layer 
thickness, and preferably about 30% of that thickness. 
The depth of the third cut should be great enough to sever the third layer 
to an extent sufficient to ensure that layer will separate on applying an 
axial force to that layer, but it is preferred for the third cut to stop 
short of the conducting second layer, to avoid risk of "nicking" that 
layer. This third layer may thus be severed to a depth of from 60% to 90% 
of that layer thickness, but preferably to a depth of about 75% of the 
layer thickness, to ensure the second layer is not affected by the cut, 
even with cables constructed with relatively low concentricity tolerances. 
In the foregoing description of the method of this invention, all the 
severed layers are removed at the same time in the final stage of the 
method. It will however be apparent that the method may be performed in 
such a way that the end portion of the layer immediately overlying the 
core may be removed from the cable at the completion of the second stage 
in which that end portion is separated by twisting, following performance 
of the first cut. Then, in the final stage of the method, only the layers 
severed by way of the second and third cuts would be removed. 
The method of this invention need not be performed with the tool described 
above, having a pivoted blade, though it does not lend itself to 
performance by simple hand tools such as a knife. For example, all that is 
required is a tool which includes a blade adjustable with respect to a 
reference surface for the cable to be cut to give the two required depths 
of cut. Such a tool may have a body defining a bore through which the 
cable is passed, there being a blade slidably mounted on the body and 
having an adjustment mechanism serving to permit the blade to be moved 
from a base position where it is clear of the bore to a first position 
giving a relatively shallow cut to a second position giving a deeper cut. 
Whichever tool is employed, it is preferred for the blade of the tool to be 
employed to impart the force required to remove the separated layers, 
before the blade is removed from the third cut. Thus, following completion 
of the third cut, but before withdrawal of the blade from that cut, a 
force should be applied to the tool axially of the cable and in the 
direction of the free end of the cable. The tool itself may also apply a 
clamping force to the severed layers immediately adjacent the third cut, 
so assisting removal of the layers. In this way, the severed layers may be 
removed, so exposing successively from the third cut towards the free end 
the second layer, the first layer and the core. 
Most conveniently, the tool is configured to provide a guide for the 
positioning of the cuts. This may be achieved by a graduated projection, 
enabling the operator to determine exactly where to position the cable 
with respect to the tool, prior to effecting a cut.

Referring initially to FIGS. 1 to 4, the cable stripping tool there shown 
has a body 10, assembled from three moulded plastics material parts 
comprising a main body 11, a cover plate 12 and a blade carrier 13. The 
main body 11 and cover plate 12 fit together to define a slot within which 
a portion of the blade carrier 13 may slide, as will be apparent from the 
following description. 
The main body 11 has a side plate 14 from which a generally U-shaped wall 
15 upstands, leaving a flange 16 projecting beyond the U-shaped wall. In 
association with the side plate 14, the inner faces of the wall 15 define 
the slot 17 within which a generally rectangular portion of the blade 
carrier 13 may slide. The moulding of the main body 11 may include 
recesses 18, to reduce the amount of plastics material employed and also 
to permit satisfactory production of the part by an injection moulding 
process, taking into account material shrinkage. 
The cover plate 12 is of substantially the same overall shape as the side 
plate 14, and has a flange 19 arranged in a similar manner to the flange 
16 of the main body 11. Five pins 20 project normally from the cover 
plate, which pins are received in bores 21 provided in the main body, to 
locate and hold the cover plate in the required position with respect to 
the main body 11. Pins 20 and bores 21 may appropriately be formed so that 
the main body and cover plate snap-fit together, or reliance may be placed 
simply on a frictional interfit between the pins and bores. Alternatively, 
the cover plate and main body may be glued together during the last stage 
of assembly of the tool. 
A bore 22 is formed through the side plate 14, which bore is of an 
appropriate diameter closely to receive the co-axial cable with which the 
tool is intended to be used. The inside face 23 of the base of the 
U-shaped wall 15 extends substantially diametrically of the bore 22, and 
that wall is provided with a semi-circular groove 24 contiguous with the 
bore 22, so as to permit a cable to be inserted through the bore 22 to the 
required extent. The cover plate 12 similarly is formed with a bore 25 
co-axial with and of the same diameter as the bore 22, and on the outer 
face of the cover plate adjacent the bore 25 there is provided a guide 
piece 26, having two guide surfaces 27 and 28, for a purpose to be 
described below. 
The blade carrier 13 has a finger portion 29 including a finger hole 30 and 
a moulding recess 31 in which may be provided for example information 
concerning the particular sizing of the tool. Projecting from the finger 
portion 29 is a blade portion 32, adapted for sliding movement within the 
slot 17 defined by the main body 11. The top face 33 of this portion 32 is 
provided with a semi-circular groove 34, centrally positioned for 
alignment with the bore 22 in the main body 11. 
The blade portion 32 of the blade carrier 13 is provided with two pins 35 
and 36 upstanding from that portion and having a cutting blade 37 
pivotally mounted on pin 35. In addition to the hole adjacent the blade 
end remote from the cutting edge 38 closely fitting on the pin 35, the 
blade has a slot 39 in which is received pin 36. When so positioned, the 
cutting edge 38 of the blade is cordal with respect to the groove 34. 
The blade 37 is of closely controlled dimensions and shape. The side edge 
of slot 39 is tangential to the hole for pin 35 and the cutting edge 38 is 
accurately honed to lie at a predetermined acute angle to the major axis 
of the slot 39, a known distance from the hole which receives the pin 35. 
In addition, the relative positions of the pins 35 and 36 with respect to 
the groove 34 of the carrier 13 are closely controlled. 
It will thus be appreciated that with the blade pivoted to the position 
shown in FIG. 3, with the pin 36 engaging the right-hand edge of the slot 
39, the amount by which the cutting edge 33 overlies the groove 34 can be 
controlled by appropriate positioning of the pin 35. When the blade has 
pivoted so that the left hand side of the slot 39 engages the pin 36 (as 
shown in FIG. 4) the amount by which the cutting edge 38 overlies the 
groove 34 is increased, but limited by the spacing between the pins 35 and 
36. Thus, complete control of the two depths of cut, with the blade in the 
two positions shown in FIGS. 3 and 4 respectively, can be achieved solely 
by appropriate positioning of the pins 35 and 36. 
As shown in FIG. 2, the pins 35 and 36 project beyond the U-shaped wall 15 
of the main body 11 to be received in a groove 40 in the cover plate 12. 
When the tool is completely assembled, this groove 40 limits the movement 
of the blade carrier 13 away from the main body 11. 
The tool is completed by means of a resilient endless band 41 passed around 
the U-shaped wall 15, between the flanges 16 and 19, and around the finger 
portion 29 of the blade carrier 13. When so positioned, the band 41 should 
be in a state of tension, so that it holds the blade carrier 13 fully 
engaged in the slot in the main body 11. To facilitate relative separation 
of the blade carrier and the main body 11 to the extent limited by pin 35 
in groove 40, finger and thumb friction grip portions 42 and 43 are 
provided respectively on the side plate 14 and cover plate 12. 
The above described tool is especially configured for use with a particular 
co-axial cable, to give a specified form of end portion preparation. When 
a cable of the correct type is to be prepared, the tool is "opened" by 
pulling the blade carrier 13 away from the main body 11 against the 
resilient bias provided by the band 41, conveniently effected by inserting 
the middle finger through finger hole 30 and grasping the body between a 
thumb and forefinger, on grips 42 and 43. Holding the tool open, the 
operator then pushes the cable through bore 22, past grooves 24 and 34 and 
through bore 25 in plate 12, to project beyond face 28. The tool is then 
released to permit the band to draw the blade carrier 13 into the main 
body, whereafter the tool is rotated in a clockwise sense (as viewed in 
FIG. 1 with the cable end-on). The drag of the blade on severing the 
layers of the cable causes the blade to move to the position illustrated 
in FIG. 4 and so the blade effects a relatively deep cut, partially 
severing the insulating first layer overlying the core of the cable. 
The tool is then opened again, and the cable pushed further through the 
bore until the cut already effected is aligned with guide surface 27 of 
the guide piece. Then, the projecting portion of the cable is twisted, 
until little resistance is felt, so indicating that the end portion of the 
insulating first layer of the cable has been completely severed. This 
action also will twist together the strands of a multi-strand core 
conductor. The tool is then rotated clockwise again, so effecting a second 
cut partially severing the insulating first layer of the cable, the blade 
acting in precisely the same manner as has been described above. 
Preferably, the tool is at this point rotated sufficiently counter 
clockwise to move the blade to the position illustrated in FIG. 3, to 
prevent the blade cutting right through the insulating third layer in the 
initial part of the next stage, described below. 
In the next stage of the operation, the tool is opened again and the cable 
pushed yet further through the bore in the tool, until the second cut is 
aligned with the second guide surface 28 of the guide piece 26. It is then 
rotated in a counterclockwise direction automatically to maintain the 
blade in the position illustrated in FIG. 3, so performing a relatively 
shallow depth of cut, severing on the outer insulating third layer of the 
cable and leaving untouched the conducting second layer and the insulating 
first layer. To complete the preparation, the tool is gripped across its 
ends, so urging the recesses 24 and 34 to clamp on to the severed part of 
the cable, and the tool is then pulled towards the free end of the cable, 
the blade still being engaged in the third cut. This pulls all of the 
severed layers clear of the cable, so leaving exposed a portion of the 
inner conductor, a length of the insulating first layer and a length of 
the conducting second layer. 
When using the tool of this invention, it will be appreciated that the 
blade need not immediately penetrate the cable to the required depth. The 
severing action may be gradual, as the tool is rotated, with the band 41 
gradually drawing the blade into the cable to the predetermined depth, as 
tool rotation is continued. Moreover, the operation of the tool is fully 
automatic in that the blade moves to either one of its two positions by 
virtue of the drag of the blade through the cable, depending on whether 
the tool is rotated clockwise or counterclockwise. 
Modification of the tool to suit different cables is relatively simple. 
Identical mouldings may be used, with the bores 22 and 25, and the grooves 
24 and 34 appropriately machined to suit the cable with which the tool is 
to be used. Moreover, the holes in the carrier to receive the pins 35 and 
36 may be jig-drilled at appropriate positions to give the required two 
depths of cut for any given cable. 
The tool also may be modified to have the blade carrier removable from the 
body, by appropriate configuration of pins 35 and 36, and of the plate 12 
in the region of slot 40. This will facilitate the changing of a blade, 
when blunted by repeated use. Spare blades may be carried in an 
appropriate recess, formed in the blade carrier for instance on the 
opposite face thereof to that from which pins 35 and 36 project. 
In a further alternative, the blade carrier 13 may include a slidable jaw 
opposed to and spring-urged towards recess 24 in the body. This jaw will 
engage the cable immediately on releasing the blade carrier, even though 
the blade may not have penetrated the cable so preventing the recess 34 
engaging the cable. Such a jaw will serve to clamp the cable against 
recess 24, and also to hold the tool square, until the blade has 
sufficiently penetrated the cable on rotating the tool. 
The method of using the tool described above will now be explained in 
greater detail, referring to FIGS. 5-I to 5-VI. Shown in those Figures is 
a cable to be stripped, comprising a copper conducting core 110, which may 
be a monofilament or multi-stranded, surrounded by a first layer 111 of an 
appropriate dielectric material, having regard to the intended use for the 
cable. The first layer 111 may comprise a solid sleeve for instance of 
polyethylene, or it may be of the air-cored variety. Closely overlying the 
first layer 111 is a conducting second layer 112, typically formed of a 
copper braid in the form of a sleeve. Again, having regard to the intended 
use of the cable, the second layer 112 may comprise two sub-layers, the 
first of which being a copper foil wound tightly around the first layer 
111 and the second of which being a braided copper sleeve. The cable 
further comprises a third layer 13, in the form of an insulating sleeve 
made from an appropriate plastics material. This sleeve, in addition to 
providing an insulating layer, may also impart to the cable advantageous 
mechanical and physical properties such as strength, abrasion resistance, 
and so on. 
Whilst the exact specification of the end portion preparation vary from 
connector to connector, in general it is necessary to expose a length of 
the conducting core 110 at the end of the cable, then a length of the 
insulating first layer 111, then a length of the conducting second layer 
112. The end portion preparation thus requires the removal of a relatively 
long length of the outer layer 113, the removal of a lesser length of the 
conducting second layer 112 and the removal of a relatively short length 
of the insulating first layer 111. 
Step I of the method comprises making an annular cut 114 (for example with 
the tool of FIGS. 1 to 4, or with the tool of FIG. 6, described below) in 
a radial plane fully around the cable to a first depth sufficient 
partially to sever the first layer 111. The first cut may lie for example 
approximately 14 mm from the end of the cable and in the case of a typical 
electric co-axial cable, may penetrate the first layer 111 to a depth of 
approximately 50% of the radial thickness of that layer. 
Step II of the method comprises rotating with a twisting motion, as shown 
by arrow A, the partially severed end portion of the cable, about the core 
110. This has the effect of separating the first layer 111 completely, as 
shown at 115. In addition, in the case of a multi-stranded core 110, this 
action also has the advantageous effect of twisting together the strands 
of the core 110. 
Step III is essentially the same as step I, in that an annular cut 116 is 
made fully around the cable in a radial plane, at a position further from 
the end of the cable than cut 114--and typically 22 mm from the end of the 
cable. Cut 116 is made to precisely the same depth as cut 114, and so 
penetrates the first layer 111 to the same extent as cut 114. 
In step IV, an annular cut 117 is made fully around the cable in a radial 
plane further from the end of the cable than cuts 114 and 116, but to a 
lesser depth than those cuts. Typically, cut 117 is positioned 30 mm from 
the end of the cable, and penetrates only the outer third layer 113, to a 
depth of about 75% of the radial thickness of that layer. 
In the final step V of the end portion preparation, a force B is applied 
axially of the cable and in the direction of the end thereof to the 
severed third layer 113, the force being applied to that severed portion 
in the region of the third cut 117. This force advantageously is applied 
by way of the knife blade used to form the cut 117, though any of a 
variety of tools could be used for this purpose--for example, a pair of 
pliers or side cutters. This force slides all the severed portions off the 
cable end portion, so leaving exposed a length of core 110, a length of 
insulating first layer 111, and a length of conducting second layer 112, 
as shown in FIG. 1-IV. 
It will be appreciated that it is an important feature of this invention 
that the depth of the first, second and third cuts 114, 116 and 117 are 
closely controlled and so the performance of this method does not readily 
lend itself to use by an operator using a free knife blade. However, a 
relatively simple tool or jig assembly for guiding the knife penetration 
can be designed to give the two depths of cut, so enabling satisfactory 
cable end portion preparation. 
A further example of a tool suitable for performing the above-described 
method of this invention is illustrated in FIG. 6. This tool comprises a 
main body 120 defining a bore 121 of a suitable diameter closely to 
receive the cable to be prepared. The body 120 also defines a slot in 
which is slidably mounted a knife blade 122, for movement in a radial 
plane with respect to the bore 121. A control knob 123 is rotatably 
mounted on the body 120, the knob driving a cam (not shown) engaged with 
the knife blade 122 within the body 120, such that rotation of the knob 
123 adjusts the amount by which the cutting edge of the knife blade 122 
intersects the bore 121. An indexing arrangement advantageously is 
provided for the knob 123, such that the knob may be positioned and remain 
at a given setting. 
Using a tool as described above permits the depth of cut of the blade 122 
to be precisely controlled in a repeatable manner and so enables 
satisfactory performance of the method of this invention as described 
above, by positioning the cable to extend through the bore 121, turning 
the knob to give the required depth of cut, and then rotating the tool 
around the cable, so severing at least some of the cable layers. 
In order to facilitate the positioning of the cuts at the correct position 
along the length of the cable, an indexing arrangement may be provided, 
projecting from the body 120 parallel to the axis of the bore 121, and 
against which the end face of the cable may be aligned each time a cut is 
to be made.