Machinery''''s Handbook 27th Episode 3 Part 1 pot

American National Standard Slotted Binding Head and Slotted Undercut Oval Countersunk Head Machine Screws ANSI B18.6.3-1972 R1991 All dimensions are in inches.. Dimensions for recess di

MACHINE SCREWS 1595

Table 11 American National Standard Slotted Binding Head and Slotted Undercut

Oval Countersunk Head Machine Screws ANSI B18.6.3-1972 (R1991)

All dimensions are in inches.

SLOTTED BINDING HEAD TYPENominal

O

Head OvalHeight,

F

SlotWidth,

J

SlotDepth,

H

TotalHeadHeight,

O

SlotWidth,

J

SlotDepth,

T

Max.,EdgeSharp

Min.,EdgeRnded

or Flat Ref Max Min Max Min Max Min

1596 MACHINE SCREWS

Table 12 Slotted Round Head Machine Screws

ANSI B18.6.3-1972 (R1991) Appendix

All dimensions are in inches.

Not recommended, use Pan Head machine screws.

ANSI Cross References for Machine Screws and Metric Machine Screw

Machine Screw Cross Recesses.—Four cross recesses, Types I, IA, II, and III, may be

used in lieu of slots in machine screw heads Dimensions for recess diameter M, width N, and depth T (not shown above) together with recess penetration gaging depths are given in

American National Standard ANSI B18.6.3-1972 (R1991) for machine screws, and in ANSI/ASME B18.6.7M-1985 for metric machine screws.

American National Standard Metric Machine Screws.—This Standard B18.6.7M

covers metric flat and oval countersunk and slotted and recessed pan head machine screws and metric hex head and hex flange head machine screws Dimensions are given in Tables

Type I Cross Recess Type IA Cross Recess Type II Cross Recess Type III Square Center

Machinery's Handbook 27th Edition

MACHINE SCREWS

Table 2 American National Standard Slotted, Cross and Square Recessed Flat Countersunk Head Metric Machine Screws

ANSI/ASME B18.6.7M-1985

All dimensions in millimeters.

For dimension B, see Table 1

For dimension L, see Table 7

Body Diameter

Body andShoulderDiameter

ShoulderDiame-ter

BodyDiame-terShoulderLength

Head Diameter

HeadHeight

UnderheadFilletRadius

SlotWidth

SlotDepthTheoretical

Machinery's Handbook 27th Edition

MACHINE SCREWS

Table 3 American National Standard Slotted, Cross and Square Recessed Oval Countersunk Head Metric Machine Screws

ANSI/ASME B18.6.7M-1985

All dimensions in millimeters.

For dimension B, see Table 1

For dimension L, see Table 7

RaisedHeadHeight

HeadTopRadius

UnderheadFilletRadius

SlotWidth

SlotDepthTheoretical

METRIC MACHINE SCREWS 1601

Table 5 American National Standard Header Points for Metric Machine Screws

Before Threading ANSI/ASME B18.6.7M-1985

All dimensions in millimeters.

The edge of the point may be rounded and the end of point need not be flat nor perpendicular to the axis of screw shank.

Threads: Threads for metric machine screws are coarse M profile threads, as given in

ANSI B1.13M (see page 1783), unless otherwise specified.

Length of Thread: The lengths of threads on metric machine screws are given in Table 1 for the applicable screw type, size, and length.

Diameter of Body: The body diameters of metric machine screws are within the limits

specified in the dimensional tables (Tables 3 through 4 and 6).

Designation: Metric machine screws are designated by the following data in the

sequence shown: Nominal size and thread pitch; nominal length; product name, including head type and driving provision; header point if desired; material (including property class, if steel); and protective finish, if required For example:

M8 × 1.25 × 30 Slotted Pan Head Machine Screw, Class 4.8 Steel, Zinc Plated M3.5 × 0.6 × 20 Type IA Cross Recessed Oval Countersunk Head Machine Screw, Header Point, Brass

It is common ISO practice to omit the thread pitch from the product size designation when screw threads are the metric coarse thread series, e.g., M10 stands for M10 × 1.5.

Nominal Screw Size

METRIC MACHINE SCREWS

All dimensions in millimeters.

A slight rounding of all edges of the hexagon surfaces of indented hex heads is permissible provided the diameter of the bearing circle is not less than the equivalent

of 90 per cent of the specified minimum width across flats dimension.

Heads may be indented, trimmed, or fully upset at the option of the manufacturer.

For dimension B, see Table 1

For dimension L, see Table 7

Table 6 (Continued) American National Standard Hex and Hex Flange Head Metric Machine Screws ANSI/ASME B18.6.7M-1985

Hex Flange Head

Min

Flange Diameter, DC

OverallHeadHeight, K

HexHeight, K1

Min,

FlangeEdgeThickness,

Cb

Min

FlangeTopFilletRadius, R1

MaxUnderhead Fillet

MaxTransitionDia, DA Radius, RMin

MACHINE SCREWS 1605

British Machine Screws.—Many of these classifications of fasteners are covered in

Brit-ish Standards B.S 57:1951, “B.A Screws, Bolts and Nuts”; BS 450:1958 (obsolescent),

“Machine Screws and Machine Screw Nuts (BSW and BSF Threads)”; B.S 1981:1953,

“Unified Machine Screws and Machine Screw Nuts”; BS 2827:1957 (obsolescent):1957,

“Machine Screw Nuts, Pressed Type (B.A and Whitworth Form Threads)”; B.S 3155:1960, “American Machine Screws and Nuts in Sizes Below 1⁄4 inch Diameter”; and

BS 4183:1967 (obsolescent), “Machine Screws and Machine Screw Nuts, Metric Series.”

At a conference organized by the British Standards Institution in 1965 at which the major sectors of British industry were represented, a policy statement was approved that urged British firms to regard the traditional screw thread systems—Whitworth, B.A and BSF—

as obsolescent, and to make the internationally-agreed ISO metric thread their first choice (with ISO Unified thread as second choice) for all future designs It is recognized that some sections of British industry already using ISO inch (Unified) screw threads may find it nec- essary, for various reasons, to continue with their use for some time: Whitworth and B.A threads should, however, be superseded by ISO metric threads in preference to an interme- diate change to ISO inch threads Fasteners covered by B.S 57, B.S 450 and BS 2827:1957 (obsolescent) eventually would be superseded and replaced by fasteners speci- fied by B.S 4183.

British Standard Whitworth (BSW) and Fine (BSF) Machine Screws.—British

Stan-dard BS 450:1958 (obsolescent) covers machine screws and nuts with British StanStan-dard Whit-worth and British Standard Fine threads All the various heads in common use in both slotted and recessed forms are covered Head shapes are shown on page 1614 and dimensions on page 1617 It is intended that this standard will eventually be superseded by B.S 4183, “Machine Screws and Machine Screw Nuts, Metric Series.”

British Standard Machine Screws and Machine Screw Nuts, Metric Series.—British

Standard BS 4183:1967 (obsolescent) gives dimensions and tolerances for: countersunk head, raised countersunk head, and cheese head slotted head screws in a diameter range from M1 (1 mm) to M20 (20 mm); pan head slotted head screws in a diameter range from M2.5 (2.5 mm) to M10 (10 mm); countersunk head and raised countersunk head recessed head screws in a diameter range from M2.5 (2.5 mm) to M12 (12 mm); pan head recessed head screws in a diameter range from M2.5 (2.5 mm) to M10 (10 mm); and square and hexagon machine screw nuts in a diameter range from M1.6 (1.6 mm) to M10 (10 mm) Mechanical properties are also specified for steel, brass and aluminum alloy machine screws and machine screw nuts in this standard.

Material: The materials from which the screws and nuts are manufactured have a tensile

strength not less than the following: steel, 40 kgf/mm2 (392 N/mm2); brass, 32 kgf/mm2(314 N/mm2); and aluminum alloy, 32 kgf/mm2 (314 N/mm2) The unit, kgf/mm2 is in accordance with ISO DR 911 and the unit in parentheses has the relationship, 1 kgf = 9.80665 Newtons These minimum strengths are applicable to the finished products Steel machine screws conform to the requirements for strength grade designation 4.8 The strength grade designation system for machine screws consists of two figures, the first is 1⁄10

of the minimum tensile strength in kgf/mm2, the second is 1⁄10 of the ratio between the yield stress and the minimum tensile strength expressed as a percentage: 1⁄10 minimum tensile

32⁄40× 100⁄1 = “8”; giving the strength grade designation “4.8.” Multiplication of these two figures gives the minimum yield stress in kgf/mm2.

Coating of Screws and Nuts: It is recommended that the coating comply with the

appro-priate part of BS 3382 “Electroplated Coatings on Threaded Components.”

yield stress minimum tensile strength - %

Machinery's Handbook 27th Edition

1606 MACHINE SCREWS

Screw Threads: Screw threads are ISO metric coarse pitch series threads in accordance

with B.S 3643 “ISO Metric Screw Threads,” Part 1, “Thread Data and Standard Thread Series.” The external threads used for screws conform to tolerance Class 6g limits (medium fit) as given in B.S 3643, “ISO Metric Screw Threads,” Part 2, “Limits and Tol- erances for Coarse Pitch Series Threads.” The internal threads used for nuts conform to tol- erance Class 6H limits (medium fit) as given in B.S 3643: Part 2.

Nominal Lengths of Screws: For countersunk head screws the nominal length is the

dis-tance from the upper surface of the head to the extreme end of the shank, including any chamfer, radius, or cone point For raised countersunk head screws the nominal length is the distance from the upper surface of the head (excluding the raised portion) to the extreme end of the shank, including any chamfer, radius, or cone point For pan and cheese head screws the nominal length is the distance from the underside of the head to the extreme end of the shank, including any chamfer, radius, or cone point Standard nominal lengths and tolerances are given in Table 5.

Lengths of Thread on Screws: The length of thread is the distance from the end of the

screw (including any chamfer, radius, or cone point) to the leading face of a nut without countersink which has been screwed as far as possible onto the screw by hand The mini- mum thread length is shown in the following table:

All dimensions are in millimeters.

Screws of nominal thread diameter M1, M1.2 and M1.4 and screws of larger diameters that are too short for the above thread lengths are threaded as far as possible up to the head

In these screws the length of unthreaded shank under the head does not exceed 11⁄2 pitches for lengths up to twice the diameter and 2 pitches for longer lengths, and is defined as the distance from the leading face of a nut that has been screwed as far as possible onto the screw by hand to: 1) the junction of the basic major diameter and the countersunk portion

of the head on countersunk and raised countersunk heads; and 2) the underside of the head on other types of heads.

Diameter of Unthreaded Shank on Screws: The diameter of the unthreaded portion of

the shank on screws is not greater than the basic major diameter of the screw thread and not less than the minimum effective diameter of the screw thread The diameter of the unthreaded portion of shank is closely associated with the method of manufacture; it will generally be nearer the major diameter of the thread for turned screws and nearer the effec- tive diameter for those produced by cold heading.

Radius Under the Head of Screws: The radius under the head of pan and cheese head

screws runs smoothly into the face of the head and shank without any step or discontinuity.

A true radius is not essential providing that the curve is smooth and lies wholly within the maximum radius Any radius under the head of countersunk head screws runs smoothly into the conical bearing surface of the head and the shank without any step or discontinuity The radius values given in Tables 1 and 2 are regarded as the maximum where the shank diameter is equal to the major diameter of the thread and minimum where the shank diam- eter is approximately equal to the effective diameter of the thread.

MACHINE SCREWS 1609

Ends of Screws: When screws are made with rolled threads, the “lead” formed by the

thread rolling operation is normally regarded as providing the necessary chamfer and no other machining is necessary The ends of screws with cut threads are normally finished with a chamfer conforming to the dimension in Fig 1a through Fig 1d At the option of the manufacturer, the ends of screws smaller than M6 (6-mm diameter) may be finished with a radius approximately equal to 11⁄4 times the nominal diameter of the shank When cone point ends are required, they should have the dimensions given in Fig 1a through Fig 1d.

Dimensions of 90-Degree Countersunk Head Screws: One of the appendices to this

Brit-ish Standard states that countersunk head screws should fit into the countersunk hole with

as great a degree of flushness as possible To achieve this condition, it is necessary for the dimensions of both the head of the screw and the countersunk hole to be controlled within prescribed limits The maximum or design size of the head is controlled by a theoretical diameter to a sharp corner and the minimum head angle of 90 degrees The minimum head size is controlled by a minimum head diameter, the maximum head angle of 92 degrees and

a flushness tolerance (see Fig 2) The edge of the head may be flat or rounded, as shown in Fig 3.

Fig 1a Rolled Thread End

(Approximate Form as Rolled)

Fig 1b Chamfer to Extend to Slightly Below the Minor Dia.

Fig 1c Cut Thread Radiused End

(Permissible on Sizes Below M6 Dia.)

Fig 1d Cone Pointed End (Permissible on Cut or Rolled Thread Screws, but Regarded as "Special")

Cut Thread Chamfered End

90

Radius Approx.

Machinery's Handbook 27th Edition

1610 MACHINE SCREWS

For dimensions, see Tables 1 through 5

British Standard Machine Screws and Machine Screw Nuts—Metric Series

Slotted Countersunk Head Machine Screws

Slotted Raised Countersunk Head Machine Screws

Slotted Pan Head Machine Screws

Slotted Cheese Head Machine Screws

Machine Screw Nuts, Pressed Type, Square and Hexagon

l k

d n

a r

90 +2

l b

D D

Edge May Be Rounded or Flat, But Not Sharp Edges

Shank Dia ≈

Effective Dia.

Shank Dia ≈

Major Dia.

t

l k f

d n

a r

90 +2

l b

D D

Edge May Be Rounded or Flat, But Not Sharp Edges

Shank Dia ≈

Effective Dia.

d n

a r D

d n

a r D

Shank Dia ≈

Major Dia Shank Dia ≈

MACHINE SCREWS 1611

Table 3 British Standard Slotted Pan Head Machine Screws—

Metric Series BS 4183:1967 (obsolescent)

All dimensions are in millimeters For dimensional notation, see diagram on page 1610 Recessed head screws are also standard and available For dimensions, see British Standard.

k

Head Radius

R

Radius Under Head

r

Transition Diameter

a

Slot Width

n

Slot Depth

t

b See Lengths of Thread on Screws on page 1606

MACHINE SCREWS

Table 4 British Standard Slotted Cheese Head Machine Screws—Metric Series BS 4183:1967 (obsolescent)

All dimensions are given in millimeters For dimensional notation, see diagram on page 1610

General Dimensions: The general dimensions and tolerances for screws and nuts are given in the accompanying tables Although slotted screw

dimensions are given, recessed head screws are also standard and available Dimensions of recessed head screws are given in BS 4183:1967 lescent).

D

HeadHeight

d a

Thread

b

ThreadRun-out

a

SlotWidth

n

SlotDepth

t

c See text following table in Lengths of Thread on Screws description in text

Pan head screw (Unified, BSW & BSF) Hexagon head screw (Unified)

Cheese head screw (BSW & BSF) Hexagon head screw (Unified) alternate design

Raised cheese head screw (Unified) Hexagon machine screw nut (Unified)

British Standard Machine Screws and Nuts (Continued)

ricc:1958 (obsolescent) and B.S 1981:1953

Machinery's Handbook 27th Edition

1616 MACHINE SCREWS

All dimensions in inches See page 1614 for a pictorial representation and letter dimensions.

British Standard Unified Machine Screws and Nuts B.S 1981:1953

80° Countersunk Head Screwsa,b

a All dimensions, except J, given for the No 4 to 3⁄8-inch sizes, incl., also apply to all the 80 ° Raised Countersunk Head Screws given in the Standard

b Also available with recessed heads

Hexagon Head Screws

1618 CAP SCREWS

CAP AND SET SCREWS

Slotted Head Cap Screws.—American National Standard ANSI/ASME B18.6.2-1998 is

intended to cover the complete general and dimensional data for the various styles of ted head cap screws as well as square head and slotted headless set screws (see page 1625) Reference should be made to this Standard for information or data not found in the follow- ing text or tables.

slot-Length of Thread: The length of complete (full form) thread on cap screws is equal to

twice the basic screw diameter plus 0.250 in with a plus tolerance of 0.188 in or an amount equal to 21⁄2 times the pitch of the thread, whichever is greater Cap screws of lengths too short to accommodate the minimum thread length have full form threads extending to within a distance equal to 21⁄2 pitches (threads) of the head.

Designation: Slotted head cap screws are designated by the following data in the

sequence shown: Nominal size (fraction or decimal equivalent); threads per inch; screw length (fraction or decimal equivalent); product name; material; and protective finish, if required Examples: 1⁄2-13 × 3 Slotted Round Head Cap Screw, SAE Grade 2 Steel, Zinc Plated .750-16 × 2.25 Slotted Flat Countersunk Head Cap Screw, Corrosion Resistant Steel.

Table 1 American National Standard Slotted Flat Countersunk Head Cap Screws

ANSI/ASME B18.6.2-1998

All dimensions are in inches.

Threads: Threads are Unified Standard Class 2A; UNC, UNF and 8 UN Series or UNRC, UNRF,

and 8 UNR Series.

EdgeRnd'd

CAP SCREWS 1619

Table 2 American National Standard Slotted Round Head Cap Screws

ANSI/ASME B18.6.2-1998

All dimensions are in inches.

Fillet Radius, U: For fillet radius see foonote to table below.

Threads: Threads are Unified Standard Class 2A; UNC, UNF and 8 UN Series or UNRC, UNRF

and 8 UNR Series.

Table 3 American National Standard Slotted Fillister Head Cap Screws

ANSI/ASME B18.6.2-1998

All dimensions are in inches.

Fillet Radius, U: The fillet radius is as follows: For screw sizes 1⁄4 to 3⁄8 incl., 031 max and 016 min.; 7⁄16 to 9⁄16, incl., 047 max., 016 min.; and for 5⁄8 to 1, incl., 062 max., 031 min.

Threads: Threads are Unified Standard Class 2A; UNC, UNF and 8 UN Series or UNRC, UNRF

and 8 UNR Series.

Height, H

TotalHead

1620 CAP SCREWS

All dimensions in inches The body length LB of the screw is the length of the unthreaded

cylindri-cal portion of the shank The length of thread, LT, is the distance from the extreme point to the last complete (full form) thread Standard length increments for screw diameters up to 1 inch are 1⁄16 inch for lengths 1⁄8 through 1⁄4 inch, 1⁄8 inch for lengths 1⁄4 through 1 inch, 1⁄4 inch for lengths 1 through 3 1⁄2

inches, 1⁄2 inch for lengths 3 1⁄2 through 7 inches, 1 inch for lengths 7 through 10 inches and for ters over 1 inch are 1⁄2 inch for lengths 1 through 7 inches, 1 inch for lengths 7 through 10 inches, and

diame-2 inches for lengths over 10 inches

Heads may be plain or knurled, and chamfered to an angle E of 30 to 45 degrees with the surface of

the flat The thread conforms to the Unified Standard with radius root, Class 3A UNRC and UNRF for screw sizes No 0 through 1 inch inclusive, Class 2A UNRC and UNRF for over 1 inch through 1

1⁄2 inches inclusive, and Class 2A UNRC for larger sizes Socket dimensions are given in Table 11 For details not shown, including materials, see ANSI/ASME B18.3-1998.

Table 4 American National Standard Hexagon and Spline Socket

Head Cap Screws ANSI/ASME B18.3-1998

Size, M

Nom Hex

SocketFillet

Ext., F

KeyEngage-menta, T

a Key engagement depths are minimum Spline socket sizes are nominal

CAP SCREWS 1621

Table 5 Drill and Counterbore Sizes For Socket Head Cap Screws (1960 Series)

All dimensions in inches.

Source: Appendix to American National Standard ANSI/ASME B18.3-1998.

CountersinkDiametera

a Countersink: It is considered good practice to countersink or break the edges of holes which are

smaller than (D Max + 2F Max) in parts having a hardness which approaches, equals or exceeds the

screw hardness If such holes are not countersunk, the heads of screws may not seat properly or the sharp edges on holes may deform the fillets on screws thereby making them susceptible to fatigue in applications involving dynamic loading The countersink or corner relief, however, should not be larger than is necessary to insure that the fillet on the screw is cleared

Close Fitb

b Close Fit: The close fit is normally limited to holes for those lengths of screws which are threaded

to the head in assemblies where only one screw is to be used or where two or more screws are to be used and the mating holes are to be produced either at assembly or by matched and coordinated tooling

Normal Fitc

c Normal Fit: The normal fit is intended for screws of relatively long length or for assemblies

involv-ing two or more screws where the matinvolv-ing holes are to be produced by conventional tolerancinvolv-ing ods It provides for the maximum allowable eccentricity of the longest standard screws and for certain variations in the parts to be fastened, such as: deviations in hole straightness, angularity between the axis of the tapped hole and that of the hole for the shank, differences in center distances of the mating holes, etc

meth-Number or

Fractional

Size

DecimalSize

Number orFractionalSizeDecimalSize

1622 CAP SCREWS

Table 6 American National Standard Hexagon and Spline Socket Flat Countersunk

Head Cap Screws ANSI/ASME B18.3-1998

All dimensions in inches.

The body of the screw is the unthreaded cylindrical portion of the shank where not threaded to the head; the shank being the portion of the screw from the point of juncture of the conical bearing sur-

face and the body to the flat of the point The length of thread LT is the distance measured from the extreme point to the last complete (full form) thread.

Standard length increments of No 0 through 1-inch sizes are as follows: 1⁄16 inch for nominal screw lengths of 1⁄8 through 1⁄4 inch; 1⁄8 inch for lengths of 1⁄4 through 1 inch; 1⁄4 inch for lengths of 1 inch through 3 1⁄2 inches; 1⁄2 inch for lengths of 3 1⁄2 through 7 inches; and 1 inch for lengths of 7 through 10 inches, incl For screw sizes over 1 inch, length increments are: 1⁄2 inch for nominal screw lengths of

1 inch through 7 inches; 1 inch for lengths of 7 through 10 inches; and 2 inches for lengths over 10 inches.

Threads shall be Unified external threads with radius root; Class 3A UNRC and UNRF series for sizes No 0 through 1 inch and Class 2A UNRC and UNRF series for sizes over 1 inch to 1 1⁄2 inches, incl.

For manufacturing details not shown, including materials, see American National Standard ANSI/ASME B18.3-1998 Socket dimensions are given in Table 11

HeightSplineSocketSize

Head-HexagonSocketSize

KeyEngage-mentTheoretical

CAP SCREWS 1623

Table 7 American National Standard Hexagon Socket and Spline

Socket Button Head Cap Screws ANSI/ASME B18.3-1998

All dimensions in inches.

These cap screws have been designed and recommended for light fastening applications They are not suggested for use in critical high-strength applications where socket head cap screws should nor- mally be used.

Standard length increments for socket button head cap screws are as follows: 1⁄16 inch for nominal screw lengths of 1⁄8 through 1⁄4 inch, 1⁄8 inch for nominal screw lengths of 1⁄4 through 1 inch, and 1⁄4 inch for nominal screw lengths of 1 inch through 2 inches Tolerances on lengths are −0.03 inch for lengths up to 1 inch inclusive For lengths from 1 through 2 inches, inclusive, length tolerances are − 0.04 inch.

The thread conforms to the Unified standard, Class 3A, with radius root, UNRC and UNRF.

To prevent interference, American National Standard ANSI/ASME B18.3.4M-1986 gives metric dimensional and general requirements for a lower head profile hexagon socket button head cap screw Because of its design, wrenchability and other design factors are reduced; therefore, B18.3.4M should be reviewed carefully Available only in metric sizes and with metric threads For manufacturing details, including materials, not shown, see American National Standard ANSI/ASME B18.3-1998

HeadHeight

HeadSideHeight

SplineSocketSizea

a Socket dimensions are given in Table 11

HexagonSocketSizeaStandardLength

HeadSideHeight NominalThreadSizeThread

ShoulderNeckDia

ShoulderNeckWidthThread NeckFillet

Head FilletExtension

Above D

HexagonSocketSize

1626 SET SCREWS

Table 10 American National Standard Hexagon and Spline Socket Set Screw

Optional Cup Points ANSI/ASME B18.3-1998

All dimensions are in inches.

The cup point types shown are those available from various manufacturers.

* This diameter may be counterbored

Nom

Size

1628 SET SCREWS

All dimensions are in inches.

*Threads: Threads are Unified Standard Class 2A; UNC, UNF and 8 UN Series or UNRC, UNRF

and 8 UNR Series.

Length of Thread: Square head set screws have complete (full form) threads extending over that

portion of the screw length which is not affected by the point For the respective constructions, threads extend into the neck relief, to the conical underside of head, or to within one thread (as mea- sured with a thread ring gage) from the flat underside of the head Threads through angular or crowned portions of points have fully formed roots with partial crests.

Table 12 American National Standard Square Head Set Screws

ANSI/ASME B18.6.2-1998

Diams., P

Point

Rad., R Dog, Q Half Dog, Q1

SET SCREWS 1629

Designation: Square head set screws are designated by the following data in the sequence shown:

Nominal size (number, fraction or decimal equivalent); threads per inch; screw length (fraction or decimal equivalent); product name; point style; material; and protective finish, if required Exam- ples: 1⁄4 - 20 × 3⁄4 Square Head Set Screw, Flat Point, Steel, Cadmium Plated .500 − 13 × 1.25 Square Head Set Screw, Cone Point, Corrosion Resistant Steel.

Cone Point Angle, Y: For the following nominal lengths, or longer, shown according to nominal

size, the cone point angle is 90 ° ± 2°: For size No 10, 1⁄4; 1⁄4, 5⁄16; 5⁄16, 3⁄8; 3⁄8, 7⁄16; 7⁄16, 1⁄2; 1⁄2, 9⁄16; 9⁄16, 5⁄8; 5⁄8, 3⁄4;

3⁄4, 7⁄8; 7⁄8, 1; 1, 11⁄8; 11⁄8, 11⁄4; 11⁄4, 11⁄2; 13⁄8, 15⁄8; and for 11⁄2, 13⁄4 For shorter screws the cone point angle is

Point Types: Unless otherwise specified, square head set screws are supplied with cup points Cup

points as furnished by some manufacturers may be externally or internally knurled Where so fied by the purchaser, screws have cone, dog, half-dog, flat or oval points as given on the following page.

speci-Point Angle, X: The point angle is 45 °, + 5°, − 0° for screws of the nominal lengths, or longer, given just above for cone point angle, and 30 ° min for shorter lengths.

Table 13 American National Standard Square Head Set Screws

Rad.,S

Neck Relief

1630 SCREW SOCKET KEYS AND BITS

Source: Appendix to American National Standard ANSI/ASME B18.3-1998.

Table 14 Applicability of Hexagon and Spline Keys and Bits

Nominal

Key or Bit

Size

Cap Screws Flat Countersunk

Head Cap Screws

Button HeadCap Screws

ShoulderScrews

SetScrewsNominal Screw Sizes

HEXAGON KEYS AND BITS

SCREW SOCKET KEYS AND BITS 1631

All dimensions are in inches The thread conforms to the Unified Standard, Class 3A, UNC and

UNF series The socket depth T is included in the Standard and some are shown here The nominal length L of all socket type set screws is the total or overall length For nominal screw lengths of 1⁄16

through 3⁄16 inch (0 through 3 sizes incl.) the standard length increment is 0.06 inch; for lengths 1⁄8

through 1 inch the increment is 1⁄8 inch; for lengths 1 through 2 inches the increment is 1⁄4 inch; for lengths 2 through 6 inches the increment is 1⁄2 inch; for lengths 6 inches and longer the increment is 1 inch Socket dimensions are given in Table 11

Length Tolerance: The allowable tolerance on length L for all set screws of the socket type is ± 0.01 inch for set screws up to 5⁄8 inch long; ± 0.02 inch for screws over 5⁄8 to 2 inches long; ± 0.03 inch for screws over 2 to 6 inches long and ± 0.06 inch for screws over 6 inches long Socket dimensions are given in Table 11

For manufacturing details, including materials, not shown, see American National Standard ANSI/ASME B18.3-1998.

Table 15 ANSI Hexagon and Spline Socket Set Screws ANSI/ASME B18.3-1998

Flat Point

Oval PointFor optional cup points and their dimensions see Table 10

Min KeyEngagementDepth Limit for Lgth.

Angle

a Reference should be made to the Standard for shortest optimum nominal lengths to which the

min-imum key engagement depths TH and TS apply

T Sa Yb

b Cone point angle Y is 90 degrees plus or minus 2 degrees for these nominal lengths or longer and

118 degrees plus or minus 2 degrees for shorter nominal lengths