Shank
Shank is an element of a press tool.The shank acts as a connecting link between the press tool and the press.
The diameter of the shank should fit into the bore in the press ram.
The shank diameter is standardised in relation with the size of the press ram bore.
The size of the bore varies from press to press depending on the capacity of the press.
The shank can be fixed to the tool top plate by
- Rivetting
- Screw thread
- Making as integral part of the top plate.
The threaded types are used commonly.
The shank has two flats milled on diameter at top to facilitate its fastening to the tool by using a spanner.
Self aligning type shank
The shank permits quick loading and unloading of the press tool on a press.The design of the shank is different from the other types.A tee coupling mechanism is made in two sections.The half mounted on the tool is the male member.The half fixed to the press ram is the female member.They are case hardened.
Location of shank on a tool
The balancing of cutting punches is very important for press tool operation.
Unbalanced force distrbution on the tool top will cause undue wear on the punch,die and also on the pillars.
The resultant force of all the cutting forces acting on different punches should pass through the shank center.
The resultant force of al the partial cutting forces can be fund by applying the following two methods.
- by calculation
- by graphical method(polygon of forces).Center point of shank location can be found by calculating the x and y oordinates for the point.The formula to be used for this calculation is x=(l1x1)+(l2x2)+(l3x3)+.../l1+l2+l3+....
y=(l1y1)+(l2y2)+(l3y3)+.../l1+l2+l3+...
Polygon System
The center point of shank location can be determined by graphical method which is also known as polygon system.To construct the polygon force diagram the sequential steps given here have to be followed.
1. Draw the cutting forces to a scale in a straight line.
2. Draw the arrow heads at the ending points of each force as shown.
3. Draw two more lines at 45degree angle from the starting and finishing points of the total length of the forces so as to form an isosceles and call the intersecting point as pole.
4. Draw the lines from each arrow head to join the pole point and call them as pole beams.
5. Draw the forces to scale at the given distance.
6. Draw the lines parallel to the pole bems,cutting force line graphically.
7. The line of action of the resultant goes through that point where those two pole beams intersect.