Cutting edge—flatting and roughness measurement—to monitor
blunting and chipping of the drill cutting edge when drilling
D. Samuel Raj
Received: 16 March 2016 /Accepted: 20 January 2017 /Published online: 6 March 2017
Springer-Verlag London 2017
Abstract Tool wear is a major challenge when drilling CFRP.
Cutting edge rounding quantifies the blunting of the cutting
edge by considering the events happening in the flank–cutting
edge–rake zone together by fitting a circle to this zone. The
two interface zones, however, undergo wear in different ways.
While the flank–cutting edge interface becomes rounded, the
rake–cutting edge interface flattens out with drilling. Two new
parameters, flank rounding (FR) and cutting edge flatting
(CEF), are introduced to measure the damage to the flank
and cutting edge, respectively. The nature of CEF and FR
variation along the cutting edge shows that both are related.
The chipping of the cutting edges is studied using a parameter
called cutting edge roughness by monitoring the cutting edge
topography. The progression of FR and cutting edge rough-
ness along the length of the cutting edge shows that chipping
may be related to the nature of FR progression. CEF could be
easily measured using a simple measuring microscope and can
be used to monitor drill wear.
Keywords Tool wear
Cutting edge rounding
Cutting edge flatting
Many of the desirable properties of carbon fiber-reinforced
polymer have made them the material of choice for today’s
aircrafts. These materials pose manufacturing challenges dis-
tinct from metals. The need to assemble these structures using
fasteners necessitates drilling of holes in them. Their hetero-
geneity, unlike metals along with the abrasive property of the
carbon fiber, is one of the major causes for their difficult to
machine characteristics—hole quality being the primary con-
cern, the other one being tool wear [1–3].
Jantunen  observed that the condition of the cutting edge
has a very significant effect on the quality of the holes pro-
duced during machining composites. All efforts to improve
the tool life are from the perspective of retaining the sharpness
of the cutting edge. The status of the cutting edge could be
monitored using a number of techniques like cutting force,
vibration, current, etc., apart from direct measurement.
Six common types of wear criteria have been reported in
drills . They are outer corner wear, flank wear, margin wear,
crater wear, chisel edge wear, and lip chipping.
It is widely reported that tool wear produces a correspond-
ing increase in the cutting forces [6, 7, 10, 11, 14, 21]. Studies
have also revealed delamination [5–11, 14, 15, 21] and poor
surface finish [9, 11, 14] produced during drilling to be the
direct consequence of higher cutting forces.
The abrasive carbon fibers cause the cutting edge to lose its
sharpness quite rapidly in turn resulting in poor hole quality
due to inefficient cutting. Several of the earlier studies on dril-
ling of composites recognized this, and flank wear has been the
predominantly used parameter to measure drill wear [11, 12,
24] mainly because of the linear progression of wear and ease
of measurement. Toolmaker’s/optical microscope has been the
most commonly used equipment to measure flank wear [11, 21,
26]. The status of the cutting edge measured in terms of flank
* D. Samuel Raj
Department of Mechanical Engineering, CEG, Anna University,
Int J Adv Manuf Technol (2017) 92:953–968