FIELD OF THE INVENTION
The present invention relates to a device for a method of drilling holes along the
chord (line parallel to the diameter of the cylindrical objects) of a solid or hollow
cylindrical object, using a magnetic fixture and a jig suiting the outer profile of
the cylindrical object. More particularly the present invention relates to a portable
device for drilling chordal holes in solid or hollow cylindrical object for fixing
wires or thermocouples on the cylindrical objects.
BACKGROUND OF THE INVENTION
Many industrial applications require drilling holes along the chord of solid or
hollow cylindrical objects for fixing wires or thermocouples on the solid or hollow
cylindrical object. These solid or hollow cylindrical objects may be at any
orientation and may be single or a part of an assembly. This operation needs to
be performed at shops or at power plants at horizontal, inclined or vertical
orientations at different angles at hundreds of locations. Hence, there is a need
to develop an easy to use, portable device consisting of jig and fixture and
method to drill holes along the chord of solid or hollow cylindrical objects that
enables accurate drilling on solid or hollow cylindrical objects at any orientation
and of any construction.
A jig and fixture used for this application at site involves welding of a clamp to the
neighboring tube and holding a heavy metal jig by tightening a screw attached to

this clamp. This approach is time consuming and requires removal of weld over
the neighboring tube after performing drilling operation at a particular location.
US 2501036 A relates to a device for drilling holes normal to the surface of
compound-curved articles such as master tooling jigs or the like,
and checking bushings therein and is not relevant to the present application.
US 4218161 A teaches "A coupling arrangement for mounting a drill jig in
selected position on a Harding-type fixture". An arm carries a drill bushing.
through which the drill passes into a work piece held by a Hardinge fixture.
Adjustment of the arm relative to the fixture is provided by the use of gauging
blocks which enable the arm to be preset. The coupling arrangement assures
proper movement and location of the bushing relative to the fixture and this
arrangement is not relevant to the present requirement.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to propose a portable device for
drilling chordal holes in solid or hollow cylindrical object for fixing wires or
thermocouples on the cylindrical objects.
Another object of the invention is to propose a portable device for drilling chordal
holes in solid or hollow cylindrical object for fixing wires or thermocouples on the
cylindrical objects in which a jig for guiding the drill bit at the required location
and at the required angle is provided.

A still another object of the invention is to propose a portable device for drilling
chordal holes in soiid or hollow cylindrical object for fixing wires or
thermocouples on the cylindrical objects which has a cost effective jig having
profile corresponding to the outer periphery of the cylindrical object the jig
being easy to change according to the profiles of the cylindrical objects of
varying diameters.
yet another object of the invention is to propose a portable device for drilling
chordal holes in solid or hollow cylindrical object for fixing wires or
thermocouples on the cylindrical objects, in which a clamping or fixing system is
provided to firmly hold the jig in position during the drilling operation.
A further object of the invention is to provide a set of tools that would be
portable and easy to use at any position.
SUMMARY OF THE INVENTION.
Accordingly, there is provided a portable device for drilling chordal holes in solid
or hollow cylindrical object for fixing wires or thermocouples on the cylindrical
objects.
Thus the device consists of a portable, magnetic V block and a jig that suits the
outer periphery of the hollow or solid cylindrical object of interest and having
guiding hole/holes for the drill bit at desired angles. The grooves in the magnetic
V block and the machined curvature of the jig corresponding the outer radius of
the cylindrical object to allow proper seating of the assembly over the job. The
magnetic intensity is adequately selected to withstand the drilling force and keep

the jig in position during the driliing. The jig and the magnetic V block are
connected together with adjustable and removable screws and links.
Thereby the drawbacks mentioned in the background are overcome by the
present invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig 1 shows the drilling of chordal hole, in a tube of a panel formed joining
multiple tubes, using the jig and fixture proposed under the present invention.
Fig 2 shows the proposed jig and fixture arrangement.
Fig. 3 shows the exploded view of the components of the proposed jig and
fixture arrangement
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING
The device meant for drilling hole along the chord of a solid or cylindrical object
is shown in Fig. 1, and comprises a magnetic V block (02) of size matching the
outer periphen/ of the cylindrical object and having sufficient magnetic strength
to withstand the drilling force and with a control to magnetize or demagnetize, a
jig (3) in the form of a sector of a hollow cylinder having inner radius equal to
the outer radius of the cylinder object to be drilled (01) and having guiding hole
at appropriate location and angle for guiding the drill bit of the desired size
during the chordal hole drilling operation. Figure 2 shows the photographic v.ew
of the jig and fixture assembly. Figure 3 shows the exploded view of the

components of the jig and fixture assembly. A plate member (04) having plurality
of holes fixed to the V-block (02) by using a fastener (06). An adjusting
means is provided for adjusting the height of the drill jig assembly and said
plate member is frxed on (04) with the help of a third bolt and nut (05).A
second plate (09) is attached to the adjusting means (07) with the help of
second fastener (10) for angular adjustment of the jig (03) which is fixed with
the second plate (09) with the help of fourth screw (12). A Ink plate (11) is
fixed on the second plate (09) with the help of a fifth screw (12). A screwed rod
(13) is fixed to link plate (11) through the adjusting means (07) to provide
sufficient force on the jig to arrest any unwanted movement/vibration of the jig
during drilling.

WE CLAIM :
1 A portable device for drilling chordal holes in solid or hollow cylindrical
object for fixing wires or thermocouples on the cylindrical objects,
comprising :
- at least one magnetic V block and one Jig having inner curvature
matching the outer periphery of the cylindrical object including a plurality
of holes configured at multiple slanting locations for guiding a drill bit of
desired size, wherein the magnetic V block has a size matching the outer
periphery of the cylindrical object to be drilled, and a sufficient magnetic
strength to withstand the drilling force including magnetizing and
demagnetizing the unit, and wherein the jig is formed of a sector of a
hollow cylinder having inner radius equal to the outer radius of the
cylindrical object to be drilled with guiding holes at spaced apart locations
for angularly guiding the drill bit during the chordal hole drilling operation.
2. The device as claimed in claim 1, wherein the V-block and the jig are
connected together using multiple connecting links, screws and nuts.