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INSTRUCTIONS AND SAFETY REGULATIONS
2.4
Checking the draw bar
The draw bar must be made of steel and with a minimum breakload of
500 N/mm_ and must be perfectly straight.
The threads at each end of the draw bar must be straight and concentric
with the other diameters.
The draw bar must be well supported with guide bushes in the spindle
bore in order to avoid damage to the operating cylinder, especially when
the cylinder is pushing (chuck clamping a component internally in a
bore). The play of the draw bar / guide bush in the spindle bore, must be
less than 0.2 mm.
ATTENTION: the movement of the central wedge, the master jaws and
the counter weights (NT series) creates a "pump" effect that could
cause the penetration of coolant and swarf into the chuck through the
seals. To avoid this, the draw bar must have an axial hole that will let the
chuck "breath" in the dry and clean area behind the spindle where the
cylinder is mounted. As an option the chuck can be pressurized with a
0.2 bar pressure, by means of a rotating joint (Deublin or similar) moun-
ted on the operating cylinder.
2.5
Mounting the chuck on the lathe spindle
IMPORTANT: The mounting bolts must be tightened properly with
a torque wrench adjusted to the dimension and the class of the bolts
(see table 2-B).
In the case of cylindrical center diameters, it is necessary to center the
chuck on the rotation axis of the spindle.
Check in accordance with the ISO 3442 norm shown below, that the
concentricity of the chuck outside diameter (A) and the flatness of the
face (B) are less than 1/2 of the spec for normal chucks, and 1/3 of the
spec for high speed chucks.
TAB. 2
Object under
Pos.
measurement
Ø a
A
Concentricity
0.04
B
Undulation
0.04
If the chuck is mounted with a special flange, it is critical that the
support face on the flange is the one inside the centering diameter of the
chuck body (where the bolts are) so that the two surfaces fit without
distorting the shape the chuck body.
Supporting on the external circular crone causes distortion of the chuck
body, blocking the movement of the internal parts, resulting in a loss of
gripping force and a faster wear.
Tab
Tightening torque for mounting bolts
2-B
of the chucks on the spindle nose
Minimum class requested 12.9
D (mm)
M (N.m)
M6
M8
M10
M12
D = Dimensions of screw
Ø a = chuck diameter (mm.)
Permissible error (mm)
160
160
Ø a
315
315
0.05
0.05
fig. 3
Minimum class requested 8.8
D (mm)
M (N.m)
12
M16
170
30
M20
300
45
M24
500
70
M30
950
M = Tightening torque
2.6
Mounting
a) Mount and center the cylinder flange number 5.
b) In case of indirect mounting of the chuck on the spindle nose, mount thechuck
adapter number 2 (T = thickness of the adapter). In case of direct mounting the
chucks adapter 2 is already mounted on the plain back of the chuck.
c) Mount the draw bar 6 on the thread of the piston rod D of the cylinder.
d) Mount the cylinder on the adapter 5 following the instruction of the cylinder's
instruction manual.
e) Connect the hydraulic tubes to the cylinder.
f) Pressurize the cylinder to bring the piston to the full forward position.
g) Check the draw bar length is correct following the instructions of drg. 2.4.
h) Pull the wedge E of the chuck to the fully back position.
i)
Position the chuck in front of the spindle nose, rotate the spindle nose and screw
the draw bar 6 into the thread of the chuck wedge E.
j)
Align the spindle driving pin in its nearest corresponding seat and push the chuck
body onto its register (note that the chuck jaws will open as this this done).
Operating the cylinder at its minimum pressure, pull the chuck onto its register or
directly onto the spindle nose.
k) Fix the chuck using the correct fixing bolts and torque settings.
Cylinder in
open position
fig. 2.4
drw.2
Ø a
630
0.06
0.06
fig. 2.6
3.
MAXIMUM DRAW-PULL - MAXIMUM STATIC GRIPPING FORCE -
DYNAMIC GRIPPING FORCE AND CENTRIFUGAL FORCE -
DRIVING TORQUE - MAXIMUM SPEED.
3.1
Maximum draw-pull.
All chucks, due to the sizes of the internal parts, are limited to a
"Maximum draw-pull" (Ft max) at the draw-bar. This value is clearly
shown in the technical features and is inscribed on the chuck face.
The "draw-pull", in case of drawing with a hydraulic cylinder, is the
multiplication of the piston area (A), the oil feeding pressure (p) and effi-
ciency (η), which can be considered 0.95.
Example: On a 215 APD -3 jaws chuck, the "max draw-pull" is 42 kN
(4200 Kgf). If the drawing is made with a 125 SIN-S cylinder (which has a
103 cm
2
IMPORTANT: NEVER apply a higher force at the draw-tube than
the rated maximum. Excessive draw-pull can cause breakage of the
internal parts of the chuck.
IMPORTANT. It is necessary to check the hydraulic circuit for
water hammering. This condition could cause breakage of the draw-
bar or the internal parts of the chuck.
Check R1 and R2
Cylinder and Chuck
in open position
Ft = A · p · 0.95
piston area) the maximum oil pressure is:
Ft
4200
p = –––––––– = ––––––––––– ≅ 39 bar
A · 0.95
103 · 0.95
Indirect mounting
Direct mounting
17
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