Technical Guidance Forms of Tool Failure and Tool Life, Turning Edition
■ Forms of Tool Failure
Classification No. Name of Failure
Major Causes of Failure
(10)
Failure Caused by Mechanical Factors Failure Caused by Thermal and
(1) to (5) (6) (7)
Flank Wear Chipping Fracture
Wear caused by the scratching effect of hard grains contained in the work material Fine breakages caused by high cutting loads or vibration Large breakage caused by the impact of an excessive mechanical force acting on the cutting edge
(9)
(8)
(4)
(11)
(5)
N
(10)
(8) (9)
Crater wear Plastic deformation Thermal cracking Built-up edges
Cutting chips removing tool material as it flows over its top rake at high temperatures Deformation of cutting edge due to softening at high temperatures Fatigue from rapid, repeated heating and cooling cycles during interrupted cutting Work material is pressure welded on the top face of the cutting edge
(6)
(7)
(2) (3)
(1)
(10) (11)
Chemical Reactions
■ Tool Wear Curve
Forms of Tool Wear
Flank wear
Crater wear on rake face
Long chips Fracture due to decreased strength
Initial wear
Burrs occur
Crater wear K T
Sudden increase in wear
Poor surface roughness
Side flank wear V N1
Rake Face Wear
Steady wear
Face flank wear V N2
Cutting Time (T) (min)
Cutting Time (T) (min)
Average flank wear V B
Flank Wear
· Wear increases rapidly right after starting cutting, then moderately and proportionally, and then rapidly again after a certain value
· Wear increases proportionately to the cutting time
Edge wear V C
Higher cutting force
Poor dimensional accuracy Burrs occur
■ Tool Life (V-T)
· This double logarithm graph shows the relative tool life (T) with the specified wear over a range of cutting speeds (Vc) on the X axis, and the cutting speed along the Y axis
Flank Wear
Crater wear
v c1
v c2
v c3
v c1
v c2
v c3
v c4
v c4
V B
K T
T 1
T 2
T 3
T 4
T' 1 T' 2
T' 3
T' 4
Cutting Time (min)
Cutting Time (min)
In v c1 In v c2 In v c3 In v c4
In v c1 In v c2 In v c3 In v c4
InT 1
InT 2
InT 3
InT 4
InT' 1
InT' 2
InT' 3
InT' 4
Lifetime (min)
Lifetime (min)
N37
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