A.V.C.COLLEGE OF ENGINEERING
DEPARTMENT OF MECHANICAL
ENGINEERING
BATCH - 10
Design and fabrication of wedge
milling fixture
Internal guide,
M.Varatharajulu, B.E.,M.B.A.,
Presented by,
Asst. professor.
 M. Chandru
External guide,
 G. Muthuthiyagarajan
S. Sivananainthaperumal,A.M.E
 C. Padmanabha
Manager(Tool Engg),
 B. Prakash
BHEL.
Objective

Design and fabrication of a wedge fixture
for ‘T’ slot and guide slot milling for gate
valve component.
Gate valve
wedge
Wedge

In BHEL gate valve has wedges from
3” to 32”.
Contd.,

The wedge is made by casting process.
 Then the ‘T’ slot and guide slot are made
by milling process in vertical milling
machine and horizontal milling machine.
 The ‘T’ slot is used to hold the wedge by
means of a stem which is normally
connected with actuator or hand wheel.
 Guide slot is used for up and down
motion of wedge inside the valve.
Side view of wedge
Problem while machining
Solution
Components of fixture
Base
plate
Angle
plate
Heat
treated plate
Strap
Clamps
Rest
screw
Fasteners
Design
Base plate:
Base plate is designed according to
the milling machine bed dimensions and angle
plate dimension. The base plate is fastened
with the bed by using ‘T’ bolts.
Dimension: 1484 X 1484
Material: IS 2062 (carbon steel)
Contd.,
Angle plate:
To make the parallel machining
surface to the machine bed the inclination
of the angle plate is set to 4.50.
Material: IS 2062 (carbon steel)
Contd.,
Heat treated plate:
It is a circular thin plate of thickness
10mm. It has the same diameter of the
Angle plate . This is gas carburized plate .
Use of the plate is to reduce the fixture
wear due to continuous loading and
unloading of work piece.
Clamp:
For this fixture we select the strap
clamp. We design the strap clamp. The
calculations are as follows.
Clamping force calculations

For any fixture the clamping force should be greater than the cutting force,
so we calculate the cutting force by the following formula.

CUTTING FORCE (FC) =
Here, K=material constant (KN/mm2), f = feed(mm/s)
d =depth of cut (mm),b =width of cut (mm)
Cs = cutting speed (mm/s).

cutting speed Cs =
=
= 7.5398 X 103 mm/s
Contd.,
Fc
=
=13,428.7 N.
 Clamping
force should be greater than the cutting force
So, Let as assume clamping force is 40000 N.
(3 times of cutting force)
Total no of clamps = 4
For each clamp clamping force should be 10000 N.
Contd.,

To get the 10000N clamping force chose the bolt
diameter from the force exerted by bolts table.(table
3.1,design of jigs, fixtures and press tools by
C.Elanchezhian book)

The range is 8227.23 – 11454.55 N. For this range the
bolt diameter is 22.23 mm. From standard bolt table
from DDB 5.49.
 From
the above M24 bolt is selected
 Material: SA193 B7 .(medium carbon steel)
Strap design
For
effective clamping the one third of the
clamp length provided in between bolt and
work piece.
Contd.,
 From
the above d = 24 (d = diameter of the bolt)
 From DDB, for M24 bolt the total length of the
clamp, B = 200 mm.
 And the 2/3 of B is the distance between rest
screw and the bolt .
A = 2/3 B
= 2/3 (200)
A = 133.33 ~ 133mm.
 And the chamfer values are taken from the DDB
 Values of A , B , d are used to find the thickness
and width, slot. The calculations are as follows,
Contd.,
 Width
(w)
w = 2.3 d +1.5748
=2.3 X 24 + 1.5748
= 56.7748 mm ~ 57mm.
 Thickness(t)
t2= 0.85 d A [1- (A/B)]
= 0.85 X 24 X 133[1-(133/200)]
t2 = 908.4196
t=30.14 mm ~ 30 mm.
 Slot width (c)
c=d+1.5748
=24+1.5748
=25.5748 ~ 26mm.
Strap clamp Orthographic view
Strap clamp isometric view
conclusion

Thus the wedge milling fixture is
designed and fabricated according to the
above discussion.
The above said problem was rectified by
our fixture.
Using this fixture the T slot and guide slot
are milled without any difficulties.
The need is fulfilled by our project.
Reference
 Design of Jigs, Fixtures and Press tools
by c.elanchezhian.

A Hand book of Fixture design- BHEL.

PSG Design data book.