FIELD OF INVENTION
The present invention relates to double taper expansion fixture for outer
diameter turning of thin walled cylinders with plain inner profile without any
deformation and the method for the same. More particularly, the invention relates to
double taper expansion fixture for outer diameter turning of thin walled cylinders
with plain inner profile with more dimensional accuracy, shape and surface finish
without any deformation.
BACKGROUND OF INVENTION
If the wall thickness is less than 7% of the inner diameter then the cylinder
may be treated as a thin one. Thin walled cylinders are used as boiler shells,
pressure tanks, pipes and in other low pressure processing equipments.
Clamping of thin walled cylinders in lathes for outer diameter turning will be
done using axial and radial clamps. The conventional axial and radial clamps will not
completely enclose the thin walled cylinder inner circumference which results in
deformation of the component due to clamping force & cutting force of the tool. The
typical deformation of the thin walled cylinder during machining in lathes using
conventional radial or axial clamps like 3 jaw chuck / clamping pad and studs is
illustrated in Fig. A & Fig. B. The deformation of the component will affect the

dimensional accuracy of the component, shape and surface finish. To overcome the
above issue it is necessary to have a fixture which should provide required clamping
force. But at the same time it should also protect the components from deformation
due to clamping force and cutting force during machining.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a Double taper
expansion fixture for outer diameter turning of thin walled cylinder, in which the thin
walled cylinder can be machined with more dimensional accuracy, shape and surface
finish without any deformation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure (A) Outer diameter turning of thin walled cylinder using radial clamp –
three jaw chuck and possible deformation according to prior art.
Figure (B) Outer diameter turning of thin walled cylinder using axial clamp –
clamping pad, studs and possible deformation according to prior art.

Figure (C) Double taper expansion fixture with thin walled cylinder loading, for
turning outer diameter of the cylinder without deformation according
to present invention.
Figure (D) Shows the components of Double taper expansion fixture.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
The present invention describes the manufacturing process and working
principle of the Double taper expansion fixture for outer diameter turning of thin
walled cylinder, in which the thin walled cylinders outer diameter can be turned in
lathes with more dimensional accuracy, shape and surface finish without any
deformation.
According to the invention, there is provided a Double taper expansion fixture
(D) as shown in FIG. C for outer diameter turning of thin walled cylinders
The double taper expansion fixture (D) consists of the following:
Base taper assembly (1):

- A base taper assembly (1) consist of a circular base plate (1A), Taper ring (IB)
and guide ring (1C) welded together as shown in FIG.C.
- The 1:10 taper turning of taper ring (1B), Inner diameter turning and clamping
holes threading on guide ring (1C) is done after welding.
- The taper ring (1B) height is maintained to have sufficient gap (G) as shown in
FIG.C to provide sliding and expansion movement on expansion sleeve (2).
Guide taper assembly (3):
- A Guide taper assembly (3) consists of a Taper ring (3A) and guide sleeve (3B)
welded together as shown in FIG.C.
- The 1:10 taper turning of taper ring (3A), Outer diameter turning and clamping
holes drilling on guide sleeve (3B) is done after welding. Through this hole, the
guide taper assembly (3) is fixed to base taper assembly (1) by means of a
clamping screws (5) in the assembly of double taper expansion fixture (D).
- The taper ring (3A) height is maintained to have sufficient gap (G) as shown in
FIG.C to provide sliding and expansion movement on expansion sleeve (2).
Expansion sleeve (2):
- An Expansion sleeve (2) in spring steel material is made with 1:10 internal
double taper to suit both base taper assembly (1) and guide taper assembly (3).
- The outer diameter of Expansion sleeve (2) is turned to have sliding fit with the
thin walled cylinder (4) inner diameter.

- The expansion sleeve height to be maintained to have sufficient gap (G) as
shown in FIG.C to obtain sliding and expansion movement by guide taper
assembly (3) and base taper assembly (1).
- A single longitudinal slit for the width of 2 to 3mm along the total length of the
expansion sleeve (2) is cut to have expansion on tightening of the clamping
screws (5), to provide the required clamping pressure on the thin walled cylinder
(4).
Clamping screws (5):
- A clamping screws (5) is are used to fasten the guide taper assembly (3) with
the base taper assembly (1) to obtain required clamping force through expansion
of expansion sleeve (2).
Working procedure of Double taper expansion fixture:
- The base taper assembly (1) is fixed in the lathe face plate or table.
- The expansion sleeve (2) is loaded in to the base taper assembly (1).
- The guide taper assembly (3) is loaded in to the expansion sleeve (2) and base
taper assembly (1).
- The clamping screw (5) fixes the guide taper assembly (3) and base taper
assembly (2) without full tightening.
- The thin walled cylinder (4) is loaded over the expansion sleeve (2).

- The clamping screw (5) is now tightened using torque wrench to obtain required
clamping pressure on the thin walled cylinder (4) by expansion of expansion
sleeve (2)
- Now the fixture is ready for outer diameter turning of the thin walled cylinder
(4).
- After completion of outer diameter turning, the clamping screws are loosen (5)
and the thin walled cylinder (4) is unloaded from the fixture.
Referring to Fig. C, The base taper assembly (1) is used to mount the fixture
over the lathe table/ face plate and allows the guide taper assembly (3) to slide in to
the guide ring (1C) which makes the expansion sleeve (2) to expand.
The double inner taper of the expansion sleeve (2) slides over the taper rings
of base taper assembly (1) and Guide taper assembly (3). On expansion the
expansion sleeve provides the required clamping force on the thin walled cylinder
which is fixed on the outer diameter of the expansion sleeve (2).
The clamping screws (5) are used to achieve the sliding movement on the
guide taper assembly (3) and base taper assembly (1). The tightening torque is
maintained using torque wrench to avoid over tightening of the thin walled Cylinder.
Since the expansion sleeve (2) completely encloses the inner circumference of the
thin walled cylinder (4), it protects the thin walled cylinder (4) from deformation due
to clamping force and cutting force of the tool.

WE CLAIM
1. A double taper expansion fixture (D) for outer diameter turning of thin walled
cylinders with plain inner profile without any deformation, the said double taper
expansion fixture (D) consisting;
a base taper assembly (1), the said base taper assembly consisting of a
circular base plate (1A), a 1:10 taper ring (1B) and guide ring (1C) welded and
machined together, the said guide ring having threaded clamping holes (6);
a guide taper assembly (3) consisting of a 1:10 taper ring (3A) and a guide
sleeve (3B) welded and machined together;
an expansion sleeve with 1:10 internal double taper to suit both base taper
assembly (1) and guide taper assembly (3) and having single slit across the
length;
a clamping screws (5) are disposed to fix the guide taper assembly (3) with
base taper assembly without full tightening,
Characterized in that,
The clamping screws are configured to obtain required clamping pressure
using a torque wrench on the thin walled cylinder (4) by causing an expansion of
expansion sleeve (2) wherein the expansion sleeve (2) is disposed in the inner

circumference of the thin walled cylinder (4) for protecting the said cylinder (4)
from deformation due to clamping force and cutting force of the tool.
2. The double taper expansion fixture (D) as claimed in claim 1, wherein the
expansion sleeve (2) is made of spring steel.
3. The double taper expansion fixture (D) as claimed in claim 1 wherein the
expansion sleeve has a single slit cut for 2 to 3 mm across the length.
4. A method for turning outer diameter of a thin walled cylinder fixed on the double
taper expansion fixture (D) as claimed in claim 1, comprising;
fixing the base taper assembly (1) on a face plate of a lathe machine;
loading the expansion sleeve (2) on to the base taper assembly (1);
loading the guide taper assembly (3) on to the expansion sleeve (2) and base
taper assembly (1);
fixing the guide taper assembly (3) and the base taper assembly by the
clamping screw (5) without full tightening;
loading the thin walled cylinder (4) over the expansion leave (2);
wherein,

the clamping screws (5) are tightened by means of a torque wrench to obtain
required clamping pressure on the thin walled cylinder (4) by expansion of
expansion sleeve (2)
wherein
the expansion sleeve (2) being completely enclosed in the inner
circumference of the thin walled cylinder protects the thin walled cylinder (4)
from deformation due to clamping force and cutting force of the tool.