38
S (mm)
Pitch
Shape
Speed
up to 2
4-6
B
shaped
2
2
÷
5
8
C
solid
2
5
÷
10
8
C
solid
1
over 10
8
C
solid
1
up to 20
8
C
solid
1
20
÷
50
10
C
solid
1
9.4 - Cutting and advance speed
The cutting speed (m/min) and the advance speed (cm
2
/min = area travelled by the blade teeth when
removing shavings) are limited by the development of heat close to the tips of the teeth.
•
The cutting speed is subordinate to the resistance of the material (R = N/mm
2
), to its hardness
(HRC) and to the dimensions of the widest section.
•
Too high an advance speed (= blade descent) tends to cause the blade to deviate from the ideal
cutting path, producing non rectilinear cuts on both the vertical and the horizontal plane.
9.5 - Running in the blade
When cutting for the first time, it is good practice to run in the blade making a series of cuts at a
low advance speed (= 30-35 cm
2
/min on material of average dimensions with respect to the cutting
capacity and solid section of normal steel with R = 410-510 N/mm
2
), generously spraying the cut-
ting area with lubricating coolant.
9.6 - Blade structure
The most commonly used blades are made of extra high speed steel (HHS) of normal quality
(HHS/DMo5) or superior quality (HHS/Mo5+Co5) with a treated tooth, which differentiates them
from the former on account of the high value of structural resistance, greater resistance to seizing,
absence of stress in the mass and a better holding of lubricating coolant during work.
9.7 - Type of blades
The blades differ essentially in their constructive characteristics, such as:
•
tooth shape
•
tooth cutting angle
Tooth shape
The profile of the toothing depends on the size, shape and thickness of the section to be cut, either
straight or at an angle. It may also vary according to the pitch, but not so distinctly as to make this
an element for classification.
•
Fine toothing is to be chosen for cutting small sections with a profiled shape and tubular sec-
tions with thin walls (2-5 mm depending on the material).
•
Large toothing is suitable for cutting medium and large solid sections or fairly thick profiled or
tubular sections (over 5 mm).
