ASTM E618-07(2013)
(Test Method)Standard Test Method for Evaluating Machining Performance of Ferrous Metals Using an Automatic Screw/Bar Machine
Standard Test Method for Evaluating Machining Performance of Ferrous Metals Using an Automatic Screw/Bar Machine
SIGNIFICANCE AND USE
5.1 This test method can be used to evaluate the machining performance of a single grade or type of metal or to compare one grade or type with another.
5.1.1 The machining performance of the test metal is measured by the maximum rate at which test pieces can be produced within specified surface roughness and dimensional limits for a specified length of time and also by the cutting speed and tool feed employed to attain that rate.
5.1.2 The relative machining performance of the various metals tested using this test method may be evaluated only at operating conditions that produce test pieces of like quality with respect to surface roughness and dimensional limits for comparable periods of machining time.
SCOPE
1.1 This test method covers a production-type test for evaluating the machining performance of ferrous metals as they are used in single-spindle or multiple-spindle automatic screw machines. It is based on producing parts of a standard design in such machines to uniform levels of quality with respect to surface roughness and size variation. The standard test piece, designed for this test, is machined from bars using a specified number of tools in a specified sequence. Nothing in this test method should be construed as defining or establishing limits of acceptability for any grade or type of metal.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E618 − 07 (Reapproved 2013)
Standard Test Method for
Evaluating Machining Performance of Ferrous Metals Using
an Automatic Screw/Bar Machine
This standard is issued under the fixed designation E618; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method was written to fill a requirement for a standard test for determining the
machinability of ferrous metals using automatic screw/bar machines. (Hereafter, these machines will
be referred to as automatic screw machines.) Although a variety of short-time laboratory tests have
demonstrated different machining characteristics among ferrous metals, it has been difficult to apply
the resulting data to commercial automatic screw machine practice.
In this test method a standard test piece is machined using tools and machining operations typical
of automatic screw machine practice.
Throughtheuseofthistestmethod,therelativemachiningperformanceofametalcanbeevaluated
even though different automatic screw machines are used. Further, comparisons can be made among
different lots of the same grade or different grades to determine relative machining performance.
1. Scope 2. Referenced Documents
1.1 This test method covers a production-type test for 2.1 American National Standard: B46.1 Surface Texture
evaluating the machining performance of ferrous metals as
3. Terminology
they are used in single-spindle or multiple-spindle automatic
screw machines. It is based on producing parts of a standard 3.1 Definitions of Terms Specific to This Standard:
3.1.1 average surface roughness (per set of samples)—for
design in such machines to uniform levels of quality with
respect to surface roughness and size variation. The standard each surface (the major and minor diameter formed surfaces)
the surface roughness per set of samples is the average of the
test piece, designed for this test, is machined from bars using
a specified number of tools in a specified sequence. Nothing in roughnesses recorded as in 3.1.5.1 for the six test pieces per
set. A test set is described in 9.3.
this test method should be construed as defining or establishing
limits of acceptability for any grade or type of metal.
3.1.2 calculated hourly production rate (in pieces per
hour)—3600s/hdividedbythecycletimeinsecondsperpiece.
1.2 The values stated in inch-pound units are to be regarded
(Unit: pieces per hour.)
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only
3.1.3 cycle time—the time in seconds per piece from bar
and are not considered standard.
feed-out to bar feed-out, or from cutoff to cutoff, during
uninterrupted operation of the machine. It includes all stock,
1.3 This standard does not purport to address all of the
machine, and tool movements.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.4 surface speed—the product of the original bar circum-
priate safety and health practices and determine the applica-
ference (in feet or metres) and the spindle speed in revolutions
bility of regulatory limitations prior to use.
per minute. (Unit: ft/min or m/min.)
3.1.5 surface-roughness average value (R )—the surface-
a
roughness average value is the mean reading around which the
This test method is under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
needle tends to dwell or fluctuate under small amplitude when
A01.15 on Bars.
Current edition approved June 1, 2013. Published June 2013. Originally
approved in 1977. Last previous edition approved in 2007 as E618 – 07. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E0618-07R13. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E618 − 07 (2013)
FIG. 1 Details of the ASTM Machinability Test Specimen and the Relative Positions of Form Tools
a continuously averaging meter is used. (Refer to 3.8.1.1 in during which this travel occurs. (Units: decimal inch or
ANSI B46.1). The surface-roughness value obtained by a decimal millimetre per revolution.)
continuously averaging digital readout meter is acceptable.
3.1.10 tool life (for a form tool)—the hours of machine time
3.1.5.1 The surface-roughness recorded for each surface on
determined from the calculated hourly production rate and the
thetestpieceisthemaximumofthesurface-roughnessaverage
total number of test pieces produced from the start of the test
values measured on that surface at a minimum of four places
to the earliest point at which the average of the recorded
equispaced around the circumference and measured as de-
surface-roughness average values or the average of sizes of the
scribed in 3.1.5.
test pieces in a sample set consistently exceed either the
3.1.6 surface-roughness range (per set of samples)—the
surface-roughness limits or the size limits specified in 9.7.1,
lowest and highest values of the surface roughnesses recorded
9.7.2, and 9.7.3 for the piece diameter produced by that tool.
for each surface as in 3.1.5.1for each set.
3.2 Machining performance in this test method is evaluated
3.1.7 surface-roughness range (per test)—the lowest and
by the following criteria:
highestvaluesofsurfaceroughnessesrecordedforeachsurface
3.2.1 Tool life as described in 3.1.10.
as in 3.1.5.1 during the test.
3.2.2 Cutting speed and tool-feed rate as described in 3.1.4
3.1.8 theoretical hourly production rate (in pieces per
and 3.1.9.
hour)—3600 s/h divided by the cycle time in seconds per piece
3.2.3 Hourly rate of production as described in 3.1.2 or
diminished by: (1) the indexing time or high-speed time in
3.1.8.
seconds per piece for a multiple-spindle machine, or (2) the
3.2.4 A test sample set is described in 9.3.
time in seconds per piece when no tools are cutting for a
4. Summary of Test Method
single-spindle machine.
3.1.9 tool feed rate—the distance traveled by the tool at a 4.1 Astandard test piece, shown in Fig. 1, is machined from
uniform rate divided by the number of spindle revolutions bar stock in an automatic screw machine.
E618 − 07 (2013)
4.2 Specified tools are used in a standard sequence to shape ness in microinches arithmetic average (AA) and having a
the test piece. Drills and form tools are used simultaneously to stroke of at least ⁄4 in. (6.35 mm).
provide a typical machining condition during the test. 6.3.1 In all cases an electric cutoff of 0.030 in. (0.8 mm) is
used. The stylus and skids of the tracer head must be
4.3 Cutting speed and tool feed rate for the metal being
compatible with a 0.030-in. (0.8-mm) cutoff. (See 3.6.2 in
tested are varied from one test run to another to determine the
ANSI B46.1 for a definition of cutoff.)
maximum rate at which test pieces can be produced for the
6.3.2 The length of trace is the maximum possible on the
specified length of time without exceeding the specified limits
surface being measured but must be at least 0.150 in. (3.81
for surface roughness and size dimensions.
mm).
4.4 When measured as specified, the level of and changes in
6.4 Micrometer(s), capable of indicating to 0.0001 in. or
surface roughness and the size of pieces produced are used to
0.002 mm.
evaluate the machining performance of the metal being tested.
6.5 Toolmaker’s Microscope or equivalent.
5. Significance and Use
6.6 Commercially Available Coolant.
5.1 This test method can be used to evaluate the machining
7. Test Specimen
performance of a single grade or type of metal or to compare
one grade or type with another.
7.1 The test specimen detailed in Fig. 1 shall be machined
5.1.1 The machining performance of the test metal is from 1-in. (25.4-mm) diameter bars.
measured by the maximum rate at which test pieces can be
7.2 Different bar sizes may be used to produce a different
produced within specified surface roughness and dimensional
size test piece provided that the material removed and the
limits for a specified length of time and also by the cutting
material remaining is in the same cross-sectional proportion as
speed and tool feed employed to attain that rate.
in the test piece shown in Fig. 1. When a different bar size is
5.1.2 The relative machining performance of the various
used a proportionate change is made in all dimensions, except
metals tested using this test method may be evaluated only at 3
thatbothformedsurfacesmustbeatleast ⁄8 in.(9.5mm)long.
operating conditions that produce test pieces of like quality
This is to ensure accurate surface-roughness measurements.
with respect to surface roughness and dimensional limits for
7.3 When a different size test piece is used the bar size and
comparable periods of machining time.
test piece dimensions shall be recorded on the test report.
6. Apparatus
8. Procedure for Machine Setup
6.1 Automatic Screw Machine:
8.1 Since there is a difference between automatic screw
6.1.1 A single-spindle automatic screw machine with a six-
machines as to how movement is conveyed to the end and side
or eight-hole turret, with adequate spindle capacity, and with
working tools, cams must be designed or selected to provide a
sufficient feed, speed, and power to machine a 1-in. round bar
uniform rate of tool feed for a distance greater than that
of free-machining, alloy or high-strength steel, or
necessary to remove the required metal. This will ensure a
6.1.2 A multiple-spindle automatic screw machine with a
uniform feed rate throughout the cut.
spindle capacity and with sufficient feed, speed, and power to
8.2 Feeds and speeds on the initial test run should be
machine 1-in. round bars of free-machining, alloy or high-
selected on the basis of experience or general guide lines for a
strength steel simultaneously at all spindles.
ferrous metal of similar composition and condition.
6.2 Metal-Cutting Tools—On the basis of current use for
8.2.1 The positive stop pressure maintained during the test
general applications for automatic screw-machine production,
shall be that which is recommended by the machine tool
two tool-steel grades (M7 for drills and M2 for form tools) are
builder.
suggested in 6.2.1 through 6.2.5. This is not intended to
8.3 Place the cutting tools so they cut in the following
preclude the use of other grades. This test method does require
sequence. The form tools and drills shall cut at the same time.
that the use of tool materials, other than those suggested, be
8.3.1 Spot drill (optional).
recorded and reported together with the reason(s) for the
8.3.2 Rough form and drill to depth with ⁄8-in. (15.88-mm)
change.
diameter drill.
6.2.1 A ⁄4-in. (19.05-mm) diameter or larger spot drill with
8.3.3 Finish form to 0.875-in. (22.22-mm) outside diameter
a 90° included point angle may be used.
11 3
anddrill ⁄32in.(8.73mm)deepwiththefirst ⁄8-in.(9.52-mm)
3 5
6.2.2 Two ⁄8-in. (9.52-mm) diameter and one ⁄8-in. (15.88-
diameter drill.
mm) diameter drills ground as specified in 8.6.
8.3.4 Drill ⁄32 in.(8.73mm)deep(throughthecutoff)with
6.2.3 Either a dovetail or a circular rough-form tool of M2
the second ⁄8-in. (9.52-mm) diameter drill.
steel designed as shown in Fig. 2.
8.3.5 An optional sequence of tooling for a single-spindle
6.2.4 Aflat, circular, or dovetail finish-form tool at least ⁄16
automatic machine uses only three drills in the turret; namely,
in. (14.29 mm) wide made from M2 steel as shown in Fig. 3.
5 3
one spot drill, one ⁄8-in. (15.88-mm) drill, and one ⁄8-in.
6.2.5 A cutoff tool as described in 8.5.
(9.52-mm) drill with double indexing of the turret between
6.3 Stylus-Type Standard Commercial Surface-Roughness- successive drilling operations.
Measuring Instrument, capable of measuring surface rough- 8.3.6 Cut off the finished piece.
E618 − 07 (2013)
FIG. 2 Details of the Tool Edge for the ASTM Rough-Form Tool
8.4 Form Tool Conditions: edge. This is coincident with the practice of avoiding a slight
8.4.1 Using the most rigid cross-slide, set the rough-form negative lip rake angle.
tool so that the part of the tool forming the 0.615 to 0.620-in.
8.4.4 When the side-clearance angle for the rough-form
(15.62 to 15.75-mm) or minor diameter will cut on center. tools is obtained by a tilted tool holder, it is recommended that
8.4.2 Set the finish-form tool to cut the rough-formed 0.900
the rough-form tool be reground in a tool holder or fixture
to 0.905-in. (22.86 to 22.99-mm) or major diameter on center having an identical angle of tilt.
and remove 0.030 in. (0.76 mm) from that diameter to form the
8.4.5 Allformtoolsmustbehardenedto63minimumHRC.
0.870 to 0.875-in. (22.10 to 22.22-mm) diameter. When a
8.5 Cutoff Tool—An appropriate commercial tool shall be
different size test piece is used, proportionately more or less
used.
metal will be removed by the finish-form tool.
8.6 Drills:
8.4.3 Grind and mount all form tools in the machine with an
8.6.1 Use solid two-flute standard length or screw-machine
effective positive top rake angle of 10°, a front clearance angle
of 5 to 12°, and, for the rough-form tool, a side-clearance angle length high-speed steel twist drills. Note any deviation that is
found necessary to conduct the test and record the reason.
of 2 to 4°. Note any deviation from these angles found
necessary and record the reason. The grinding lay (direction of 8.6.2 Included (point angles) angles shall be 118° for all
dominate linear surface texture) on the rake face of the rough metals except stainless steels and high-strength metals, when a
and finish form tools shall run parallel to the leading cutting 135° included angle shall be used.
E618 − 07 (2013)
NOTE 1—Angle C: 10° positive back-rake angle when mounted in cutting position.
NOTE 2—Angle D: 5 to 12° clearance angle when mounted in cutting position.
FIG. 3 Details of the Tool Edge for the ASTM Finish-Form Tool
8.6.2.1 The lip clearance angles shall be 14 6 2° for the each time a variance pattern of sizes develops which departs
⁄8-in. (9.52-mm) drill(s) with 118° included angle; 12 6 2° for from the norm previously established.
the ⁄8-in. (15.88-mm) drill with 118° included angle; 12 6 2°
9.1.1 If the machine is not capable of producing pieces
for the ⁄8-in. drill(s) with the 135° included angle; and 10 6 2°
...
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