The Lathe And Its Construction
A lathe is a machine tool used primarily for producing surfaces of
revolution and flat edges,Based on their purpose,construction,number
of tools that can simultaneously be mounted and degree of automation,
lathes-or,more accurately,lathe-type machine tools-can be classified as
follows:
1 )Engine lathes
2)Toolroom lathes
3)Turret lathes
4)Vertical turning and boring mills
5 )Automatic lathes
6)Special purpose lathes
In spite of that diversity of lathe type machine tools,they all have
common features with respect to construction and principle of operation.
These features can best be illustrated by considering the commonly used
representative type,the engine lathe,Following is a description of each
of the main elements of an engine lathe,which is shown in Fig,3,1.
Unit 3 TURNING
? Lathe bed.
? Headstock,
The lathe bed is the main frame,involving a horizontal beam on
two vertical supports,It is usually made of grey or nodular east iron
to damp vibrations and is made by casting,It has guideways to allow
the carriage to slide easily lengthwise,The height of the lathe bed
should be appropriate to enable the technician to do his or her job
easily and comfortably.
The headstock is fixed at the left hand side of the lathe bed and
includes the spindle whose axis is parallel to the guideways(the slide
surface of the bed),The spindle is driven through the gearbox,which
is housed within the headstock,The function of the gearbox is to
provide a number of different spindle speeds ( usually 6 up to 18
speeds),Some modern lathes have headstocks with infinitely variable
spindle speeds,which employ frictional,electrical,or hydraulic drives.
? Tailstock,
The spindle is always hollow,i,e.,it has a through hole extending
lengthwise,Bar stocks can be fed through that hole if continuous
production is adopted,Also,that hole has a tapered surface to allow
mounting a plain lathe center,The outer surface of the spindle is
threaded to allow mounting of a chuck,a face plate,or the like.
The tailstock assembly consists basically of three parts,its lower
base,an intermediate part,and the quill,The lower base is a casting that
can slide on the lathe bed along the guideways,and it has a clamping
device to enable locking the entire tailstock at any desired location,
depending upon the length of the workpicce,The intermediate part is a
casting that can be moved transversely to enable alignment of the axis of
the tailstock with that of the headstock,The third part,the quill,is a
hardened steel tube,which can be moved longitudinally in and out of the
intermediate part as required,This is achieved through the use of a
handwheel and a screw,around which a nut fixed to the quill is engaged.
The hole in the open side of the quill is tapered to enable mounting of
lathe centers or other tools like twist drills or boring bars,The quill can
? The carriage,
The main function of the carriage is mounting of the cutting tools and
generating longitudinal and/or cross feeds,It is actually an H-shaped
block that slides on the lathe bed between the headstock and tailstock
while being guided by the V-shaped guideways of the bed,The carriage
can be moved either manually or mechanically by means of the apron
and either the feed rod or the lead screw.
When cutting screw threads,power is provided to the gearbox of the
apron by the lead screw,In all other turning operations,it is the feed rod
that drives the carriage,The lead screw goes through a pair of half
nuts,which are fixed to the rear of the apron,When actuating a certain
lever,the half nuts are clamped together and engage with the rotating
lead screw as a single nut,which is fed,together with the carriage,along
the bed,When the lever is disengaged,the half nuts are released and the
carriage stops,On the other hand,when the feed rod is used,it supplies
power to the apron through a worm gear,The latter is keyed to the feed
rod and travels with the apron along the feed rod,which has a keyway
extending to cover its whole length.
A modern lathe usually has a quick-change gearbox located under the
headstock and driven from the spindle through a train of gears,It is
connected to both the feed rod and the lead screw and enables selecting
a variety of feeds easily and rapidly by simply shifting the appropriate
levers,The quick-change gearbox is employed in plain turning,facing
and thread cutting operations,Since that gearbox is linked to the
spindle,the distance that the apron (and the cutting tool) travels for each
revolution of the spindle can be controlled and is referred to as the feed.
LATHE CUTTING TOOLS
The shape and geometry of the lathe tools depend upon the purpose for
which they are employed,Turning tools can be classified into two main
groups,namely,external cutting tools and internal cutting tools,Each of
these two groups include the following types of tools,
? Facing tools,
? Turning tools,
Turning tools can be either finishing or rough turning tools,Rough
turning tools have small nose radii and are employed when deep cuts
are made,On the other hand,finishing tools have larger nose radii and
are used for obtaining the final required dimensions with good surface
finish by making slight depths of cut,Rough turning tools can be right-
hand or left-hand types,depending upon the direction of feed,They can
have straight,bent,or offset shanks.
Facing tools are employed in facing operations for machining plane
side or end surfaces,There are tools for machining left-hand-side
surfaces and tools for right-hand-side surfaces,Those side surfaces
are generated through the use of the cross feed,contrary to turning
operations,where the usual longitudinal feed is used
? Cutoff tools,
Cutoff tools,which are sometimes called parting tools,serve to
separate the workpiece into parts and/or machine external annual
grooves.
? Thread-cutting tools
Thread-cutting tools have either triangular,square,or trapezoidal
cutting edges,depending upon the cross section of the desired thread.
Also,the plane angles of these tools must always be identical to those
of the thread forms,Thread-cutting tools have straight shanks for
external thread cutting and are of the bent-shank type when cutting
internal threads.
? Form tools,
Form tools have edges especially manufactured to take a certain
form,which is opposite to the desired shape of the machined
workpiece,An HSS tool is usually made in the form of a single piece,
contrary to cemented carbides or ceramic,which are made in the
form of tips,The latter are brazed or mechanically fastened to steel
shanks,Fig,3,2 indicates an arrangement of this latter type,which
includes the carbide tip,the chip breaker,the pad,the clamping screw
(with a washer and a nut),and the shank, As the name suggests,the
function of the chip breaker is to break long chips every now and then,
thus preventing the formation of very long twisted ribbons that may
cause problems during the machining operation.
The carbide tips (or ceramic tips)can
have different shapes,depending upon the
machining operations for which they are
to be employed,The tips can either be
solid or with a central through hole,
depending whether brazing or
mechanical clamping is employed for
mounting the tip on the shank.
LATHE OPERATIONS
? Cylindrical turning,
In the following section,we discuss the various machining operations
that can he performed on a conventional engine lathe,It must be borne
in mind,however,that modern computerized numerically controlled
lathes have more capabilities and can do other operations,such as
contouring,for example,Following are conventional lathe operations.
Cylindrical turning is the simplest and the most common of all lathe
operations,A single full turn of the workpiece generates a circle whose
center falls on the lathe axis;this motion is then reproduced numerous
times as a result of the axial feed motion of the tool,The resulting
machining marks are,therefore,a helix having a very small pitch,which is
equal to the feed,Consequently,the machined surface is always
cylindrical.
The axial feed is provided by the carriage or the compound rest,either
manually or automatically,whereas the depth of cut is controlled by the
cross slide,In roughing cuts,it is recommended that large depths of
cuts(up to 1/4in,or 6mm,depending upon the workpiece material) and
smaller feeds be used,On the other hand,very fine feeds,smaller depths
of cut(less than 0.05in,or 0.4 mm),and high cutting speeds are preferred
for finishing cuts.
? Facing,
? Groove cutting,
The result of a facing operation is a flat surface that is either the
whole end surface of the workpiece or an annular intermediate surface
like a shoulder,During a facing operation,feed is provided by the cross
slide,whereas the depth of cut is controlled by the carriage or
compound rest,Facing can be carried out either from the periphery
inward or from the center of the workpiece outward,It is obvious that
the machining marks in both cases take the form of a spiral,Usually,it
is preferred to clamp the carriage during a facing operation,since the
cutting force tends to push the tool (and,of course,the whole
carriage)away from the workpiece,In most facing operations,the
workpiece is held in a chuck or on a face plate.
In cut-off and groove-cutting operations,only cross feed of the tool
is employed,The cut-off and grooving tools,which were previously
discussed,are employed
Boring and internal turning.
Taper turning
Boring and internal turning are performed on the internal surfaces
by a boring bar or suitable internal cutting tools,If the initial workpiece
is solid,a drilling operation must he performed first,The drilling tool is
held in the tailstock,and the latter is then fed against the workpiece.
Taper turning is achieved by driving the tool in a direction that is not
parallel to the lathe axis but inclined to it with an angle that is equal to
the desired angle of the taper,Following are the different methods used
in taper-turning practice:
(1) Rotating the disc of the compound rest with an angle equal to half
the apex angle of the cone,Feed is manually provided by cranking the
handle of the compound rest,This method is recommended for taper
turning of external and internal surfaces when the taper angle is
relatively large
(2) Employing special form tools for external,very short,conical
surfaces,The width of the workpiece must he slightly smaller than that of
the tool,and the workpiece is usually held in a chuck or clamped on a
face plate,In this case,only the cross feed is used during the machining
process and the carriage is clamped to the machine bed,
(3) Offsetting the tailstock center,This method is employed for external
taper turning of long workpieces that are required to have small taper
angles (less than 8° ),The workpiece is mounted between the two
centers; then the tailstock center is shifted a distance S in the direction
normal to the lathe axis,
(4) Using the taper-turning attachment,This method is used for turning
very long workpieces,when the length is larger than the whole stroke of
the compound rest,The procedure followed in such cases involves
complete disengagement of the cross slide from the carriage,which is
then guided by the taper-turning attachment,During this process,the
automatic axial feed can he used as usual,This method is recommended
for very long workpieces with a small cone angle.i,e.,8° through 10°,
Thread cutting.
When performing thread cutting,the axial feed must he kept at a
constant rate,which is dependent upon the rotational speed(rpm) of the
workpiece,The relationship between both is determined primarily by the
desired pitch of the thread to be cut,
As previously mentioned,the axial feed is automatically generated when
cutting a thread by means of the lead screw,which drives the carriage.
When the lead screw rotates a single revolution,the carriage travels a
distance equal to the pitch of the lead screw,Consequently,if the
rotational speed of the lead screw is equal to that of the spindled,(i.e.,
that of the workpiece),the pitch of the resulting cut thread is exactly
equal to that of the lead screw,The pitch of the resulting thread being cut
therefore always depends upon the ratio of the rotational speeds of the
lead screw and the spindle:
ioe a r in g r a tc a r r ia g e gs p in d le - to
d s c r e wr p m o f le a
w o r k p ic c er p m o f th e
k p ie c etc h o f w o rD e s ir e d p i
r e wh e le a d s cP it c h o f t
??
?
Knurling,
This equation is useful in determining the kinematic linkage between
the lathe spindle and the lead screw and enables proper selection of the
gear train between them.
In thread-cutting operations,the workpiece can either be held in the
chuck or mounted between the two lathe centers for relatively long
workpieces,The form of the tool used must exactly coincide with the
profile of the thread to be cut,i,e.,triangular tools must be used for
triangular threads,and so on.
Knurling is mainly a forming operation in which no chips are produced,
It involves pressing two hardened rolls with rough file-like surfaces
against the rotating workpiece to cause plastic deformation of the
workpiece metal.
Knurling is carried out to produce rough,cylindrical (or conical)
surfaces,which are usually used as handles,Sometimes,surfaces are
knurled just for the sake of decoration; there are different types of
patterns of knurls from which to choose.
Cutting Speeds and Feeds
The culling speed,which is usually given in surface feet per minute
(SFM ),is the number of feet traveled in the circumferential direction by
a given point on the surface (being cut )of the workpiece in 1 minute,The
relationship between the surface speed and rpm can be given by the
following equation:
where D=the diameter of workpiece in feet
N=the rpm
The surface cutting speed is dependant primarily upon the material
being machined as well as the material of the cutting tool and can be
obtained from hand books,information provided by cutting tool
manufacturers,and the like,Generally,the SFM is taken as 100 when
machining cold-rolled or mild steel,as 50 when machining tougher
metals,and as 200 when machining softer materials,For aluminum,the
SFM is usually taken as 400 or above,There are also other variables
that affect the optimal value of the surface cutting speed,These include
the tool geometry,the type of lubricant or coolant,the feed,and the
depth of cut,As soon as the cutting speed is decided upon,the rotational
speed (rpm)of the spindle can be obtained as follows:
DNS F M π?
D
S F M
N
?
?
The selection of a suitable feed depends upon many factors,
such as the required surface finish,the depth of cut,and the
geometry of the tool used,Finer feeds produce better surface
finish,whereas higher feeds reduce the machining time during
which the tool is in direct contact with the workpiece,Therefore,
it is generally recommended to use high feeds for roughing
operations and finer feeds for finishing operations,Again,
recommended values for feeds,which can be taken as guidelines,
are found in handbooks and in information booklets provided by
cutting tool manufacturers.
A lathe is a machine tool used primarily for producing surfaces of
revolution and flat edges,Based on their purpose,construction,number
of tools that can simultaneously be mounted and degree of automation,
lathes-or,more accurately,lathe-type machine tools-can be classified as
follows:
1 )Engine lathes
2)Toolroom lathes
3)Turret lathes
4)Vertical turning and boring mills
5 )Automatic lathes
6)Special purpose lathes
In spite of that diversity of lathe type machine tools,they all have
common features with respect to construction and principle of operation.
These features can best be illustrated by considering the commonly used
representative type,the engine lathe,Following is a description of each
of the main elements of an engine lathe,which is shown in Fig,3,1.
Unit 3 TURNING
? Lathe bed.
? Headstock,
The lathe bed is the main frame,involving a horizontal beam on
two vertical supports,It is usually made of grey or nodular east iron
to damp vibrations and is made by casting,It has guideways to allow
the carriage to slide easily lengthwise,The height of the lathe bed
should be appropriate to enable the technician to do his or her job
easily and comfortably.
The headstock is fixed at the left hand side of the lathe bed and
includes the spindle whose axis is parallel to the guideways(the slide
surface of the bed),The spindle is driven through the gearbox,which
is housed within the headstock,The function of the gearbox is to
provide a number of different spindle speeds ( usually 6 up to 18
speeds),Some modern lathes have headstocks with infinitely variable
spindle speeds,which employ frictional,electrical,or hydraulic drives.
? Tailstock,
The spindle is always hollow,i,e.,it has a through hole extending
lengthwise,Bar stocks can be fed through that hole if continuous
production is adopted,Also,that hole has a tapered surface to allow
mounting a plain lathe center,The outer surface of the spindle is
threaded to allow mounting of a chuck,a face plate,or the like.
The tailstock assembly consists basically of three parts,its lower
base,an intermediate part,and the quill,The lower base is a casting that
can slide on the lathe bed along the guideways,and it has a clamping
device to enable locking the entire tailstock at any desired location,
depending upon the length of the workpicce,The intermediate part is a
casting that can be moved transversely to enable alignment of the axis of
the tailstock with that of the headstock,The third part,the quill,is a
hardened steel tube,which can be moved longitudinally in and out of the
intermediate part as required,This is achieved through the use of a
handwheel and a screw,around which a nut fixed to the quill is engaged.
The hole in the open side of the quill is tapered to enable mounting of
lathe centers or other tools like twist drills or boring bars,The quill can
? The carriage,
The main function of the carriage is mounting of the cutting tools and
generating longitudinal and/or cross feeds,It is actually an H-shaped
block that slides on the lathe bed between the headstock and tailstock
while being guided by the V-shaped guideways of the bed,The carriage
can be moved either manually or mechanically by means of the apron
and either the feed rod or the lead screw.
When cutting screw threads,power is provided to the gearbox of the
apron by the lead screw,In all other turning operations,it is the feed rod
that drives the carriage,The lead screw goes through a pair of half
nuts,which are fixed to the rear of the apron,When actuating a certain
lever,the half nuts are clamped together and engage with the rotating
lead screw as a single nut,which is fed,together with the carriage,along
the bed,When the lever is disengaged,the half nuts are released and the
carriage stops,On the other hand,when the feed rod is used,it supplies
power to the apron through a worm gear,The latter is keyed to the feed
rod and travels with the apron along the feed rod,which has a keyway
extending to cover its whole length.
A modern lathe usually has a quick-change gearbox located under the
headstock and driven from the spindle through a train of gears,It is
connected to both the feed rod and the lead screw and enables selecting
a variety of feeds easily and rapidly by simply shifting the appropriate
levers,The quick-change gearbox is employed in plain turning,facing
and thread cutting operations,Since that gearbox is linked to the
spindle,the distance that the apron (and the cutting tool) travels for each
revolution of the spindle can be controlled and is referred to as the feed.
LATHE CUTTING TOOLS
The shape and geometry of the lathe tools depend upon the purpose for
which they are employed,Turning tools can be classified into two main
groups,namely,external cutting tools and internal cutting tools,Each of
these two groups include the following types of tools,
? Facing tools,
? Turning tools,
Turning tools can be either finishing or rough turning tools,Rough
turning tools have small nose radii and are employed when deep cuts
are made,On the other hand,finishing tools have larger nose radii and
are used for obtaining the final required dimensions with good surface
finish by making slight depths of cut,Rough turning tools can be right-
hand or left-hand types,depending upon the direction of feed,They can
have straight,bent,or offset shanks.
Facing tools are employed in facing operations for machining plane
side or end surfaces,There are tools for machining left-hand-side
surfaces and tools for right-hand-side surfaces,Those side surfaces
are generated through the use of the cross feed,contrary to turning
operations,where the usual longitudinal feed is used
? Cutoff tools,
Cutoff tools,which are sometimes called parting tools,serve to
separate the workpiece into parts and/or machine external annual
grooves.
? Thread-cutting tools
Thread-cutting tools have either triangular,square,or trapezoidal
cutting edges,depending upon the cross section of the desired thread.
Also,the plane angles of these tools must always be identical to those
of the thread forms,Thread-cutting tools have straight shanks for
external thread cutting and are of the bent-shank type when cutting
internal threads.
? Form tools,
Form tools have edges especially manufactured to take a certain
form,which is opposite to the desired shape of the machined
workpiece,An HSS tool is usually made in the form of a single piece,
contrary to cemented carbides or ceramic,which are made in the
form of tips,The latter are brazed or mechanically fastened to steel
shanks,Fig,3,2 indicates an arrangement of this latter type,which
includes the carbide tip,the chip breaker,the pad,the clamping screw
(with a washer and a nut),and the shank, As the name suggests,the
function of the chip breaker is to break long chips every now and then,
thus preventing the formation of very long twisted ribbons that may
cause problems during the machining operation.
The carbide tips (or ceramic tips)can
have different shapes,depending upon the
machining operations for which they are
to be employed,The tips can either be
solid or with a central through hole,
depending whether brazing or
mechanical clamping is employed for
mounting the tip on the shank.
LATHE OPERATIONS
? Cylindrical turning,
In the following section,we discuss the various machining operations
that can he performed on a conventional engine lathe,It must be borne
in mind,however,that modern computerized numerically controlled
lathes have more capabilities and can do other operations,such as
contouring,for example,Following are conventional lathe operations.
Cylindrical turning is the simplest and the most common of all lathe
operations,A single full turn of the workpiece generates a circle whose
center falls on the lathe axis;this motion is then reproduced numerous
times as a result of the axial feed motion of the tool,The resulting
machining marks are,therefore,a helix having a very small pitch,which is
equal to the feed,Consequently,the machined surface is always
cylindrical.
The axial feed is provided by the carriage or the compound rest,either
manually or automatically,whereas the depth of cut is controlled by the
cross slide,In roughing cuts,it is recommended that large depths of
cuts(up to 1/4in,or 6mm,depending upon the workpiece material) and
smaller feeds be used,On the other hand,very fine feeds,smaller depths
of cut(less than 0.05in,or 0.4 mm),and high cutting speeds are preferred
for finishing cuts.
? Facing,
? Groove cutting,
The result of a facing operation is a flat surface that is either the
whole end surface of the workpiece or an annular intermediate surface
like a shoulder,During a facing operation,feed is provided by the cross
slide,whereas the depth of cut is controlled by the carriage or
compound rest,Facing can be carried out either from the periphery
inward or from the center of the workpiece outward,It is obvious that
the machining marks in both cases take the form of a spiral,Usually,it
is preferred to clamp the carriage during a facing operation,since the
cutting force tends to push the tool (and,of course,the whole
carriage)away from the workpiece,In most facing operations,the
workpiece is held in a chuck or on a face plate.
In cut-off and groove-cutting operations,only cross feed of the tool
is employed,The cut-off and grooving tools,which were previously
discussed,are employed
Boring and internal turning.
Taper turning
Boring and internal turning are performed on the internal surfaces
by a boring bar or suitable internal cutting tools,If the initial workpiece
is solid,a drilling operation must he performed first,The drilling tool is
held in the tailstock,and the latter is then fed against the workpiece.
Taper turning is achieved by driving the tool in a direction that is not
parallel to the lathe axis but inclined to it with an angle that is equal to
the desired angle of the taper,Following are the different methods used
in taper-turning practice:
(1) Rotating the disc of the compound rest with an angle equal to half
the apex angle of the cone,Feed is manually provided by cranking the
handle of the compound rest,This method is recommended for taper
turning of external and internal surfaces when the taper angle is
relatively large
(2) Employing special form tools for external,very short,conical
surfaces,The width of the workpiece must he slightly smaller than that of
the tool,and the workpiece is usually held in a chuck or clamped on a
face plate,In this case,only the cross feed is used during the machining
process and the carriage is clamped to the machine bed,
(3) Offsetting the tailstock center,This method is employed for external
taper turning of long workpieces that are required to have small taper
angles (less than 8° ),The workpiece is mounted between the two
centers; then the tailstock center is shifted a distance S in the direction
normal to the lathe axis,
(4) Using the taper-turning attachment,This method is used for turning
very long workpieces,when the length is larger than the whole stroke of
the compound rest,The procedure followed in such cases involves
complete disengagement of the cross slide from the carriage,which is
then guided by the taper-turning attachment,During this process,the
automatic axial feed can he used as usual,This method is recommended
for very long workpieces with a small cone angle.i,e.,8° through 10°,
Thread cutting.
When performing thread cutting,the axial feed must he kept at a
constant rate,which is dependent upon the rotational speed(rpm) of the
workpiece,The relationship between both is determined primarily by the
desired pitch of the thread to be cut,
As previously mentioned,the axial feed is automatically generated when
cutting a thread by means of the lead screw,which drives the carriage.
When the lead screw rotates a single revolution,the carriage travels a
distance equal to the pitch of the lead screw,Consequently,if the
rotational speed of the lead screw is equal to that of the spindled,(i.e.,
that of the workpiece),the pitch of the resulting cut thread is exactly
equal to that of the lead screw,The pitch of the resulting thread being cut
therefore always depends upon the ratio of the rotational speeds of the
lead screw and the spindle:
ioe a r in g r a tc a r r ia g e gs p in d le - to
d s c r e wr p m o f le a
w o r k p ic c er p m o f th e
k p ie c etc h o f w o rD e s ir e d p i
r e wh e le a d s cP it c h o f t
??
?
Knurling,
This equation is useful in determining the kinematic linkage between
the lathe spindle and the lead screw and enables proper selection of the
gear train between them.
In thread-cutting operations,the workpiece can either be held in the
chuck or mounted between the two lathe centers for relatively long
workpieces,The form of the tool used must exactly coincide with the
profile of the thread to be cut,i,e.,triangular tools must be used for
triangular threads,and so on.
Knurling is mainly a forming operation in which no chips are produced,
It involves pressing two hardened rolls with rough file-like surfaces
against the rotating workpiece to cause plastic deformation of the
workpiece metal.
Knurling is carried out to produce rough,cylindrical (or conical)
surfaces,which are usually used as handles,Sometimes,surfaces are
knurled just for the sake of decoration; there are different types of
patterns of knurls from which to choose.
Cutting Speeds and Feeds
The culling speed,which is usually given in surface feet per minute
(SFM ),is the number of feet traveled in the circumferential direction by
a given point on the surface (being cut )of the workpiece in 1 minute,The
relationship between the surface speed and rpm can be given by the
following equation:
where D=the diameter of workpiece in feet
N=the rpm
The surface cutting speed is dependant primarily upon the material
being machined as well as the material of the cutting tool and can be
obtained from hand books,information provided by cutting tool
manufacturers,and the like,Generally,the SFM is taken as 100 when
machining cold-rolled or mild steel,as 50 when machining tougher
metals,and as 200 when machining softer materials,For aluminum,the
SFM is usually taken as 400 or above,There are also other variables
that affect the optimal value of the surface cutting speed,These include
the tool geometry,the type of lubricant or coolant,the feed,and the
depth of cut,As soon as the cutting speed is decided upon,the rotational
speed (rpm)of the spindle can be obtained as follows:
DNS F M π?
D
S F M
N
?
?
The selection of a suitable feed depends upon many factors,
such as the required surface finish,the depth of cut,and the
geometry of the tool used,Finer feeds produce better surface
finish,whereas higher feeds reduce the machining time during
which the tool is in direct contact with the workpiece,Therefore,
it is generally recommended to use high feeds for roughing
operations and finer feeds for finishing operations,Again,
recommended values for feeds,which can be taken as guidelines,
are found in handbooks and in information booklets provided by
cutting tool manufacturers.
