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DEBURRING and
EDGE FINISHING
HANDBOOK
Society of
Manufacturing
Engineers
LaRoux K. Gillespie
American
Society of
Mechanical
Engineers
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Copyright ©1999
Society of
Manufacturing
Engineers
1
Overview of Deburring and Edge FFinishing
inishing TTechnology
echnology
One dictionary defines a burr as “a thin ridge or
area of roughness produced in cutting or shaping
metal.” For most people, this definition conveys the
basic idea of a burr. However, for engineers charged
with removing burrs from manufactured parts,
a process known as “deburring,” this definition is
inadequate.
What constitutes a “burr-free” part varies among
companies and quality control departments. For some, it
means having no loose materials at an edge. For others,
it means having nothing visible to the naked eye or an edge
condition that will not cause any functional problem in the
next assembly process. Missing material or a hump of
rounded metal at an edge may or may not be called a burr.
Burrs and sharp edges create many problems. Sharp edges
can be the result of inadvertently leaving a sharp edge or
can come from producing a burr that typically has many
sharp facets. Burrs on sheet metal parts, for example, cause
premature tearing during forming. Plating over burrs and
sharp edges allows early corrosion of the material or a poor
fit during assembly. Fine burrs left by grinding automotive
cylinders can cause engine failure. Undetected burrs on life
safety devices can undermine performance. Every automotive mechanic has received cuts and bruises from burrs and
sharp edges left on automotive components. Edge quality is
of concern for the performance, safety, cost, and appearance
of a part. The following is a reasonably complete list of the
problems caused by improperly finished edges:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Cut hands in assembly or disassembly.
Interference fits in assemblies.
Jammed mechanisms.
Scratched mating surfaces that allow seals to leak.
Increased or changed friction (not allowable in some
assemblies).
Increased wear on moving or stressed parts.
Electrical short circuits.
Cut wires from sharp edges and sharp burrs.
Unacceptable high-voltage breakdown of dielectric.
Irregular electrical and magnetic fields.
“Detuning” of microwave systems.
Metal contamination in aerospace assemblies.
Clogged filters and ports from loose burr accumulation.
Cut rubber seals and O-rings.
Excessive stress concentrations.
Plating buildup at edges.
Paint buildup from electrostatic spray over burrs.
Paint thinout over sharp edges from liquid paints.
Edge craters, fractures, and crumbling from initially
nonsmooth edges.
Turbulence and nonlaminar flow.
• Reduced formability.
• Inaccurate dimensional measurements.
After examining the preceding list, it is not surprising
that burr technology and edge finishing is a vast and complex world. Burrs have physical properties and thus have
various acceptable deburring processes. Furthermore,
deburring is a manufacturing cost, and there are trade-offs
between cost and product quality. The process of developing
common definitions and standards across plants, industries,
and countries is still in its early stages.
Although this handbook largely concerns burr removal,
many of the following chapters also discuss edge finishing.
It is important to recognize that a product may need more
than simply having the burr removed. Typically, some specific edge configuration is also required. This handbook covers the major elements that designers must consider in the
deburring and edge finishing process, including the requirements of typical industrial parts and processes applicable
from microscopic features to earth-moving equipment. The
single missing aspect of edge finishing that is not covered is
edge sharpening, such as for knife and razor-blade edges.
This chapter provides an overview of burr technology, and
specific topics are covered in more detail in later chapters.
The chapter begins with a discussion of burr properties such
as material properties, machining properties, and part configurations. It proceeds to an introduction of burr standards.
Industrially significant and research deburring processes are
introduced, and typical costs and operation are discussed.
1.1 FUND
AMENT
ALS
FUNDAMENT
AMENTALS
The fundamental principles of burr technology rely on a
few simple concepts. The first principle encompasses the
following:
• Burr properties are a function of material properties,
machining and blanking process, and part configuration.
• Acceptable deburring is a function of burr properties,
part configuration, acceptance standards, and deburring process parameters.
• Cost-effective deburring is a function of acceptable
deburring quality; scheduled quantities; cycle time; and
environmental, safety, and health issues.
• All deburring processes have side effects.
The second principle involves five basic approaches to
reducing deburring costs:
• Improving product design.
• Preventing burrs.
• Minimizing burr properties.
• Removing burrs during the machining and blanking cycle.
• Developing or obtaining better deburring processes.
The third principle recognizes that edge finishing and
edge quality are two different aspects of deburring.
The fourth principle recognizes the vast number of processes and process variations used for deburring. Users have
over 100 deburring and edge finishing processes from which
to choose.
The fifth principle recognizes that subtle tricks of the
trade can produce major savings by eliminating the need for
new machines, training, and maintenance of high-tech equipment. In deburring and edge finishing, innovation is the key
to success.
1.2 BURR PROPERTIES
The first key to reducing edge issues is minimizing burr
size. When burrs are small, deburring requires little thought
and effort. If a burr is only .0001 in. thick 3 .0001 in. tall
(2.5 3 2.5 µm), it can be removed in a few seconds on any
part using any process. In contrast, when a burr is .005 in.
thick 3 .005 in. tall (127 3 127 µm) and part tolerances are
critical, carefully conceived approaches to removal are required. Figure 1-1 illustrates how manual deburring time
increases as burr thickness increases for a simple shape on
precision parts. A typical burr size in many operations is
.003 in. thick at the root 3 .010 in. high (76.2 3 254 µm).
Chapter 4 discusses the different types of burrs, describes
how they form, and provides essential information on minimizing them.
1.2.1 Material PProperties
roperties
Two factors related to workpiece material are directly
linked to burr size: (1) the ductility of the workpiece material and (2) the strain-hardening exponent of the material.
Large burrs cannot form in brittle materials. Cast irons,
for example, often have edges with no visible burrs. These
materials have values of elongation of 0.5–3.0% in a 2 in.
(50 mm) gage length. Since the material has little capacity
for plastic deformation, large burrs cannot form. If, however, the cutting tool heats the cast iron enough to change
its structure and the material is no longer brittle at the edges
of machined surfaces, a noticeable burr can form.
Burr size is also a function of the strain-hardening exponent (or strain-hardening coefficient) (Datsko 1966).
Nonstrain-hardening materials will form burrs, but they will
be considerably smaller than those formed on materials having large strain-hardening tendencies. As the strain-hardening exponent increases, burr thickness generally increases,
but the relationship is not usually directly proportional. (The
terms strain hardening and work hardening are synonymous.) Table 1-1 presents typical data on material properties related to burr size that are useful in estimating
burr-forming tendencies.
As a general rule, so-called aerospace materials (high
nickel-content materials) form large burrs. The key factor,
again, is high ductility in the material. Thus, stainless steel
that work hardens easily will have high strain-hardening
exponents and will easily form burrs—very large burrs in
some instances.
Dull tools can significantly heat a part while being machined, causing normally small burrs to become monstrous.
Figure 1-1. Hand-deburring time as a function of burr thickness on precision miniature parts (Wick and Veilleux 1985).
Table 1-1. Material properties related to burr size
Material
Yield strength
(ksi)
Tensile strength
(ksi)
Cast iron
55
80
6
1020 steel
30
55
25
Elongation (%)
Strain-hardening
exponent
Burr tendency
0
Low
0.22
Medium
303 Se Stainless
60
180
50
0.56
High
Kovar
50
105
72
0.42
High
Hiperco 50
57
57
0
Low
BeCu
95
102
26
0.10
Medium
2024 Aluminum
11
27
20
0.15
Medium
Copper (soft)
10
32
45
0.50
High
4340 Steel
69
108
22
0.09
Medium
Vanadium (annealed)
66
78
20
0.35
High
0.78
(Datsko 1966; Gillespie 1977a; Wick and Veilleux 1982)
The underlying cause of these monster burrs is poor control
of machining, but dull tools increase part temperatures,
which further increases ductility and subsequently burr
thickness.
1.2.2 Effects of Machining and Blanking
Processes
Typical burrs are not the result of poor planning or poor
engineering. They are a natural result of machining and
blanking processes. Large burrs, however, may be the result of poor planning. For example, the cost of burr removal
may be increased when certain machining or blanking processes are selected. They may also result from choices made
in other manufacturing operations. The sequence in which
dimensions are machined or blanked affects the location of
burrs and the effort required to remove them. Inattention
to tool sharpness can make deburring by traditional means
impossible. Feeds, speeds, depths of cut, cutter geometry,
sequence of cutter paths, and even machine tool design and
repair affect burr sizes and consequently the cost of burr
removal. Chapter 4 discusses the impact of process variables on burr sizes. Chapter 5 provides a complete look at
how several products can be machined to reduce deburring
costs. Clearly, high feed rates will typically, but not always,
increase burr dimensions. Processes that normally employ
rough-and-finish passes to hold tolerances also tend to have
smaller burrs, because the finish passes are taken at smaller
tooth or chip loads.
The geometry of cutters also plays an important role in
burr production. With over 50 designs of countersink cutters alone, not surprisingly some cutters produce smaller
burrs than others do. The challenge is to find the most costeffective cutters. From a business viewpoint, cost effectiveness includes the costs of removing burrs and finishing the
surface as well as producing the specific feature. Chapter 3
provides insight into preventing burrs.
1.2.3 E
ar t Configuration
Eff fects of PPa
A variety of strategies and some software exists for designing parts and processes so that burrs are a less-costly
problem. Part configuration affects the bottom line in
three ways:
1. It defines geometry conditions that do not produce
burrs.
2. It defines geometry conditions that produce smaller
burrs.
3. It defines simple approaches to putting burrs where
they can be easily removed at the least cost.
Chapter 5 provides basic guidance on the effects of part
geometry on burr formation. The chapter provides an example of how the angles at which a milling cutter traverses
a part (and the angles on the part) can affect burr size and
shape. Other examples show how simple design changes can
prevent the need for removing burrs. Although the topic of
part configuration is not simple, the many examples provided in later chapters may prevent hundreds of hours of
unnecessary effort.
Part geometry affects not only burr size but also the ease
of burr removal. Figure 1-2 provides a simple analysis of the
impact of angles. The ratchet wheel shown in Figure 1-2
has milled teeth; a blanked contour would involve similar
deburring issues. Note that the angle at different teeth
ranges from R1 to R4, and each angle is significantly different from the others. Mechanical deburring, such as tumbling processes, work on each edge for the same amount of
time (at least in this example). Because of the angle differences, each edge after deburring will have a different radius, though it may not have had a burr initially. The center
hole will also have a somewhat different radii than the other
edges. If each edge begins with a different-sized burr (a common occurrence), the final edges will have even more differences. These differences are the result of part-geometry
1.3 EDGE ST
AND
ARDS
STAND
ANDARDS
Figure 1-5 illustrates two edge conditions: a burr-laden
edge and a rounded edge after removal of a burr. Deburring
has many levels and variations, as shown in Table 1-2. This
variation suggests the need for some form of edge standard,
including a definition of “burr-free.” The edge quality requirements listed in Table 1-2 are examples of product needs
and illustrate why a simple “burr-free” note on a drawing
does not adequately reflect product needs.
Clearly articulating desired edge conditions is a low-cost
strategy for reducing deburring and edge finishing costs. As
obvious as it sounds, however, companies continue to omit
this simple step in their battle against the burr. Nevertheless, as customer expectations increase, clear standards are
becoming more important.
To illustrate the range of standards, consider the case of
manufacturers and researchers who identify the microscopic
slivers left on ground surfaces (surfaces, not edges) as burrs.
One company reportedly checks for burrs at 4003 magnification. The idea of burr-free parts is meaningless without some reference to inspection approaches. Omitting
reference to magnification levels of inspection does not necessarily or legally imply “when viewed with the aided eye.”
One company uses no magnification, another 103, and another 40–1003.
What exactly does the term burr-free mean? Without
clearly written, detailed, and uniform burr and edge finishing standards, we will continue to face unexpected scrap and
functional problems. The lack of uniform standards creates
three problems today:
Figure 1-2. Phosphor bronze ratchet and edge radii produced by centrifugal barrel finishing (Gillespie 1978).
effects. For some products, the differences in edge results
are not critical. For critical applications, the choice of
deburring approaches becomes much more difficult.
The number of edges on a part and the total length of
edges to be deburred on a single part may not be apparent.
Both of these factors provide some measure of the difficulty of obtaining perfect edges when high precision is
required. Figure 1-3 shows that a single gear tooth has
10 different line segments that must be burr-free. For a
miniature instrument gear small enough to fit under a
fingernail and having 12 teeth, 120 edge segments must be
burr-free.
Figure 1-4 illustrates a simple fine-pitch 5.8 3 0.35-5h
mm screw that is .320 in. (8 mm) long. It has 17 threads
with 24.4 in. (620 mm) of burrs on the crests. This small
part has over 24.8 in. (629.9 mm) of thread to deburr! A
burr left anywhere on its crest could jam its mating part.
The burrs on a single part of this design could, if broken
off into loose particles of .00076 in. (0.019 mm) diameter or
length, produce 32,632 particles.
1. The lack of detailed definitions of what is and is
not a burr cause many parts to be rejected when they
should not be rejected and some to pass when they should
not pass. The cost of both actions is enormous. Every
company has faced the problem of an inspector, floor
supervisor, or engineer arguing about whether the
small speck on the part is a burr or only “raised material.” Needless to say, the lost time, unnecessary rework, and confusion is expensive.
2. The lack of a concrete and detailed understanding of
edge needs (as opposed to merely knowing word definitions) causes overzealous deburring, which can waste
tens of millions of dollars each year. Failing to meet
real needs causes scratches, cuts, tears, product failures, assembly-line stoppages, excessive scrap, cycle
time delays, and widespread frustration on the part of
everyone in manufacturing.
3. Constantly changing, undocumented standards create
unnecessary expense and delays. People may argue
about whether a burr is normal or atypical or whether
it is the same size as it was yesterday. “You accepted it
last week, why won’t you accept it today?” is a common refrain. Even if the words in the specifications do
not change, if they exist, the implementation of standards may change daily. How does this happen? Every
Figure 1-3. Line segments on a gear tooth (Gillespie 1982).
Figure 1-4. Fine-pitch screw (5.8 × 0.35-5h) has over 2 ft of burrs on its crests.
Figure 1-5. Definition of edge conditions (Takazawa and Kato 1997).
Table 1-2. Overview of edge quality requirements
Class
Grade
Drawing definition
Radius tolerance
E0
Exceptional
high-quality edge
0.0002R
0.01–0.02 mm
E1
High-quality edge
0.002R
0.3–5 mm
E2
Sharp edge
0.02R
E3
Rounded edge
E4
Chamfered edge
E5
Dull edge
(Takazawa and Kato 1997)
Qualitative evaluation
Quantitative evaluation
Typical application
Interference microscope SEM
Diamond microtome
knife edge
Cuts paper
Universal tool microscope,
profile measuring machine,
light section
Edge of cutting tools,
edge of dies
8–30 mm
Cuts fingernail
Same as above
Hydraulic orifice edge
0.2R or chamfer
0.08–0.3 mm
Will not cut finger
Stereo microscope
Replica measurements
Mechanical parts,
gyro pivots, piston rings,
hydraulic spools
0.5R or chamfer
0.4–0.6 mm
Naked eye,
magnifying glass
Optical comparator
Mechanical parts
No cut fingers
UL sharpness gage
Some automotive parts
time a personnel change occurs in inspection, engineering, or manufacturing, a wealth of knowledge regarding intent and practice is lost. Furthermore,
memories fade over time on some long-approved
issues. Written standards, when consistently used, can
prevent this problem.
Chapter 2 provides an overview of standards as well as
references to additional works on this topic.
1.4 DEBURRING PROCESSES
Figure 1-6 illustrates the most commonly used deburring
processes. Unfortunately, no single machine or process produces all the required edge quality on every edge for every
burr without side effects. Table 1-3 outlines the known
deburring processes in use worldwide. Each process has a
segment of the edge finishing business to which it is particularly well suited. Some of the more common approaches,
as well as some less common but novel approaches, are outlined in the following section.
1.4.1 Mass
-finishing PProcesses
rocesses
Mass-finishing
Vibratory deburring has been a mainstay of finishing for
several decades, but today centrifugal disk machines (also
called roll flow by some manufacturers) are encroaching on
the popularity of vibratory machines because of their faster
action. Barrel tumbling, another mass-finishing process, is
still a major force in finishing some plastic eyeglass parts
and other metal operations. Centrifugal barrel finishing is
the fastest of the mass-finishing processes, but it is a batch
process, whereas others, such as vibratory deburring, can
be continuous-flow processes.
Which type of mass-finishing machine is the most cost
effective continues to be debated and may depend on how
knowledgeable the vendors and users are. Almost any existing process can be made more effective, and valid comparisons of output or costs depend on a clear understanding of
how the comparison is being made. Comparing a poorly operated process with a new, optimized process will produce a
different result than comparing an existing process that has
been optimized with the new process.
Figure 1-6. Principal deburring processes and their removal mechanisms.
Table 1-3. Known deburring processes (1997)a
Process
Quantity in U
.S
U.S
.S..
Abrasive finishing (A)b
Barrel tumbling (Al)
Loose belt tumbling (A1A)
Vibratory finishing (A2)
Vibratory shaker mixer finishing (A2s)
Roll-flow (centrifugal disk) finishing (A3)
Centrifugal barrel finishing (A4)
Spindle finishing (A5)
Vibratory spindle finishing (A5a)
Fluidized bed spindle finishing (A5a)
Recipro finishing (A6)
Orboresonant finishing (A7)
Flow finishing (A8)
Cascading media (A9)
Chemical loose abrasive
finishing (AC)
Chemical barrel tumbling (AC l)
Chemical vibratory finishing (AC2)
Chemical roll-flow (centrifugal disk) finishing (AC3)
Chemical centrifugal barrel finishing (AC4)
Chemical spindle finishing (AC5)
Chemical fluidized bed spindle finishing (AC5a)
Chemical recipro finishing (AC6)
Chemical orboresonant finishing (AC7)
Chemical flow finishing (AC8)
Cryogenic loose abrasive
finishing (ACRY)
Cryogenic barrel tumbling (ACRYL)
Cryogenic vibratory finishing (ACRY2)
Cryogenic vibratory shaker mixer finishing (ACRY2s)
Cryogenic roll-flow (centrifugal disk) finishing (ACRY3)
Cryogenic centrifugal barrel finishing (ACRY4)
Cryogenic spindle finishing (ACRY5)
Cryogenic fluidized bed spindle finishing (ACRY5a)
Cryogenic recipro finishing (ACRY6)
Cryogenic orboresonant finishing (ACRY7)
Cryogenic flow finishing (ACRY8)
Magnetic loose abrasive
finishing (AM)
Chemical magnetic loose
abrasive finishing (AMC)
Quantity worldwide
8,000
10
12,000
15
300
1,000
500
0
1
0
5
5
35
16,000
50
30,000
30
500
2,000
1,200
20
40
5
10
10
50
100
200
5
10
0
0
0
0
0
200
400
10
20
0
0
0
0
0
50
50
0
0
0
0
0
0
0
0
90
90
0
0
0
0
0
0
0
0
Magnetic abrasive barrel finishing (Aml)
Magnetic abrasive vibratory finishing (AM2)
Magnetic abrasive spindle finishing (AM5)
Magnetic abrasive cylindrical finishing (AM5a)
Magnetic abrasive tube-ID finishing (AM5b)
Magnetic abrasive ball finishing (AM5c)
Magnetic abrasive special shape finishing (AM5d)
Magnetic abrasive prismatic finishing (AM7)
Mixed metal fiber magnetic finishing (AM8)
5
0
0
0
0
0
0
0
0
400
0
5
5
5
5
5
5
1
Chemical magnetic abrasive barrel finishing (AMCL)
Chemical magnetic abrasive vibratory finishing (AMC2)
Chemical magnetic abrasive spindle finishing (AMC5)
Chemical magnetic abrasive cylindrical finishing (AMC5a)
0
0
0
0
0
0
0
0