Machine Design Databook 2010 Part 5 pptx

8-10 and 8-11 as per ASME Power Boiler Code The maximum allowable working pressure for stayed flat plates as per ASME Power Boiler Code For all allowable stresses in stay and stay bolts A

The thickness of a blank unstayed full-hemispherical

head with the pressure on the concave side

The formula for the minimum thickness of head when

the required thickness of the head given by Eqs (9-9)

and (9-10) exceeds 35 percent of the inside radius

UNSTAYED FLAT HEADS AND COVERS

The minimum required thickness of flat unstayed

circular heads, covers and blind flanges as per

ASME Power Boiler Code

The minimum required thickness of flat unstayed

circular heads, covers or blind flange which is

attached by bolts causing edge moment Fig 8-9( j )

as per ASME Power Boiler Code

For details of bolt load HG, bolt moments, gasket

materials, and effect of gasket width on it

The minimum required thickness of unstayed heads,

covers, or blind flanges of square, rectangular,

ellipti-cal, oblong segmental, or otherwise noncircular as per

ASME Power Boiler Code

For values y, C, and
sarefer to Tables 7-1, 7-3, and 7-6

p

ð9-13Þwhere

C ¼ a factor depending on the method of attachment

of head on the shell, pipe or header (refer toTable 8-6 for C)

d ¼ diameter or short span, measured as shown inFig 8-9

h ¼ d½Cp=
saþ 1:78WhG=
sad31=2 ð9-14Þwhere

W ¼ total bolt load, kN (lbf )

hG¼ gasket moment arm, Fig 8-13 and Table 8-22.Refer to Tables 8-20 and 8-22 and Fig 8-13

t or h ¼ d ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

ZCp=
sap

ð9-15Þ

The minimum required thickness of unstayed

non-circular heads, covers, or blind flanges which are

attached by bolts causing edge moment Fig 8-9 as

per ASME Power Boiler Code

The required thickness of stayed flat plates (Figs 8-10

and 8-11) as per ASME Power Boiler Code

The maximum allowable working pressure for stayed

flat plates as per ASME Power Boiler Code

For all allowable stresses in stay and stay bolts

Also for detail design of different types of heads,

covers, openings and reinforcements, ligaments, and

bolted flanged connection

COMBUSTION CHAMBER AND

FURNACES

Combustion chamber tube sheet

The maximum allowable working pressure on tube

sheet of a combustion chamber where the crown

sheet is suspended from the shell of the boiler as per

ASME Power Boiler Code

pt¼ maximum pitch, m (in), measured betweenstraight lines passing through the centers of thestay bolts in the different rows

(Refer to Table 9-7 for pitches of stay bolts.)

c5¼ a factor depending on the plate thickness andtype of stay (Refer to Table 8-15 for values of

c5.)For
sarefer to Tables 8-8, 8-23, and 8-11

p ¼h

2
sac5

p2 i

ð9-18ÞRefer to Chapter 8

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DESIGN OF POWER BOILERS

The vertical distance between the center lines of tubes

in adjacent rows where tubes are staggered

For minimum thickness of shell plates, dome plates,

and tube plates and tube sheet for firetube boiler

For mechanical properties of steel plates of boiler

D ¼ least horizontal distance between tube centers on

a horizontal row, in

di¼ inside diameter of tube, in

P ¼ maximum allowable working pressure, psi

P ¼ 186hðD
diÞ

where p in MPa; h, D, di, and w in m

Dva¼ ð2diD þ di2Þ1=2 ð9-20Þwhere diand D have the same meaning as givenunder Eq (9-19)

Mechanical properties of steel plates for boilers

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DESIGN OF POWER BOILERS

Plain circular furnaces

FURNACES 300 mm (12 in) TO 450 mm (18 in)

OUTSIDE DIAMETER, INCLUSIVE

Maximum allowable working pressure for furnaces

not more than 41

2 diameters in length or heightwhere the length does not exceed 120 times the thick-

ness of the plate

The maximum allowable working pressure for

fur-naces not more than 41diameter in length of height

where the length exceeds 120 times the thickness of

the plate

Circular flues

The maximum allowable external pressure for riveted

flues over 150 mm (6 in) and not exceeding 450 mm

(18 in) external diameter, constructed of iron or steel

plate not less than 6 mm (0.25 in) thick and put

together in sections not less than 600 mm (24 in) in

length

The formula for maximum allowable external

pres-sure for riveted, seamless, or lap-welded flues over

450 mm (18 in) and not exceeding 700 mm (28 in)

external diameter, riveted together in sections not

less than 600 mm (24 in) nor more than 31

2times theflue diameter in length, and subjected to external pres-

D ¼ outside diameter of furnace, in

L ¼ total length of furnace between centers of headrivet seams, in

T ¼ thickness of furnace walls, sixteenth of an inch

where p in psi; h and d in in

d ¼ external diameter of flue, in

The maximum allowable working pressure for

seam-less or welded flues over 125 mm (5 in) in diameter

and including 450 mm (18 in)

(a) Where the thickness of the wall is not greater

than 0.023 times the diameter as per ASME

Power Boiler Code

(b) Where the thickness of the wall is greater than

0.023 times the diameter

Equations (9-24) and (9-25) may applied to riveted

flues of the size specified provided the section are

not over 0.91 m (3 ft) in length and the efficiency ()

of the joint

where p in psi and d in in

h ¼ thickness of wall in 1.5 mm (0.06 in)

where p in MPa; h and D in m

p ¼ maximum allowable working pressure

D ¼ outside diameter of flue

h ¼ thickness of wall of flue

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DESIGN OF POWER BOILERS

THE MAXIMUM ALLOWABLE PRESSURE

FOR SPECIAL FURNACES HAVING

WALLS REINFORCED BY RIBS, RINGS,

AND CORRUGATIONS

(a) Furnaces reinforced by Adamson rings

(b) Another expression for the maximum allowable

working pressure when plain horizontal flues

are made in sections not less than 450 mm

(18 in) in length and not less than 8 mm (5

16in) inthickness (Adamson-type rings)

where p in psi; h and d in in

h ¼ thickness of tube wall, mm (in), not to be lessthan 11 mm (0.44 in)

Ring-reinforced type

The required wall thickness of a ring-reinforced

fur-nace of flue shall not be less than that determined

by the procedure given here

The allowable working pressure (Pa)

The required moment of inertia (Is) of circumferential

stiffening ring

The required moment of inertia of a stiffening ring

shall be determined by the procedure given here

The expression for B

The value of factor A

Assume a value for h (or t) and L Determine theratios L=Doand Do=t

Following the procedure explained in Chap 8, mine B by using Fig 9-1 Compute the allowableworking pressure Paby the help of Eq (9-32)

deter-Pa¼ðDB

where Do¼ outside diameter of furnace or flue, inCompare Pawith P If Pais less than P select greatervalue of t (or h) or smaller value of L so that Paisequal to or greater than P, psi

Is¼

LD2o



t þAsL

A

where

Is¼ required moment of inertia of stiffening ringabout its neutral axis parallel to the axis of thefurnace, in4

As¼ area of cross section of the stiffening ring, in2

A ¼ factor obtained from Fig 9-1Assume the values of Do, L, and t (or h) of furnace.Select a rectangular member to be used for stiffeningring and find its area Asand its moment of inertia I.Then find the value of B from Eq (9-34)

I, for the section selected above, select a new sectionwith a larger moment of inertia and determine anew value of Is If the required Isis smaller than themoment of inertia I selected as above, then thatsection should be satisfactory

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DESIGN OF POWER BOILERS

FIGURE 9-1 Chart for determining wall thicknesses of ring reinforced furnaces when constructed of carbon steel (specified

ASME Boiler and Pressure Vessel Code, Section I, 1983 and ‘‘Rules for Construction of Pressure Vessels,’’ Section VIII,

Corrugated furnaces

The maximum allowable working pressure (P) on

corrugated furnace having plain portion at the ends

not exceeding 225 mm (9 in) in length

Stayed surfaces

The maximum allowable working pressure (P) for a

stayed wrapper sheet of a locomotive-type boiler

16in) for Purves and other furnacescorrugated by sections not over 450 mm (18 in)long

D ¼ mean diameter, inValues of C6are taken from Table 9-10

P ¼ 11000t

R
P

where

t ¼ thickness of wrapper sheet, in

R ¼ radius of wrapper sheet, in

 ¼ minimum efficiency of wrapper sheet throughjoints or stay holes

the outer corrugation is not more than one-half of the suspension curve

(1.5 in) deep, measured from the least inside greatest outside diameter of the corrugations and having the ends fitted into the other and substantially riveted together, provided the plain parts at the ends do not exceed 300 mm (12 in)

in length

Source: ASME Power Boiler Code, Section I, 1983.

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DESIGN OF POWER BOILERS

The longitudinal pitch between stay bolts or between

the nearest row of stay bolts and the row of rivets at

the joints between the furnace sheet and the tube

sheet or the furnace sheet and the mud ring

Cross-sectional area of diagonal stay (A)

The total cross-sectional area of stay tubes which

support the tube plates in multitubular boilers

P

s sin  ¼ summated value of transverse spacing(s sin ) for all crown stays considered in onetransverse plane and on one side of the verticalaxis of the boiler

s ¼ transverse spacing of crown stays in the crownsheet, in

 ¼ angle any crown stay makes with the vertical axis

2

USCS ð9-37aÞwhere

t ¼ thickness of furnace sheet, in

R ¼ outside radius of furnace, in

P ¼ maximum allowable working pressure, psi

L ¼



2:535  109

t2PR

2

SI ð9-37bÞwhere P in Pa; t, L, and R in m

A ¼aL

where

a ¼ sectional area of direct stay, m (in)

L ¼ length of diagonal stay, m (in)

l ¼ length of line drawn at right angles to boiler head

or a projection of L on a horizontal surfaceparallel to boiler drum, m (in)

At¼ðA
aÞP

sa

ð9-39Þwhere

A ¼ area of that portion of tuber plate containingthe tubes, m (in)

a ¼ aggregate area of holes in the tube plate, m2(in2)

P ¼ maximum allowable working pressure, Pa(psi)

sa¼ maximum allowable stress value in the tubes,MPa (psi) j>48 MPa (7 kpsi)

sais also taken from Table 8-23The pitch of stay tubes shall conform to Eqs (9-17)and (9-18) and using the values of C7 as given inTable 9-11

The pitch from the stay bolt next to the corner to

the point of tangency to the corner curve for stays

at the upper corners of fire boxes shall be as given

T ¼ thickness of plate in sixteenths of an inch

P ¼ maximum allowable working pressure, psi

C7¼ factor for the thickness of plate and type of stayused

pt¼ 7592

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

C7ðT2=pÞp

angularity of tangent linesðÞ

SI ð9-40bÞwhere ptand T in m, and p in Pa

Refer to Table 9-11

HG

ranges from 35 to 45 in firetube boilers;

37 is a good working value ð9-41aÞS

P¼0:92 to 1:12 m2(10 to 12 ft2) forexternally fired boiler per hp

¼ 0:74 m2(8 ft2) for Scotch boiler per hp ð9-41eÞ

TABLE 9-11

Values ofC7for determining pitch of stay tubes

Pitch of stay tubes in the bounding rows

When tubes have nuts not outside of plates

When tubes are fitted with nuts outside of plates

Where every tube in the bounding rows is a stay tube and

each alternate tube has a nut

Source: ASME Power Boiler Code, Section I, 1983.

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DESIGN OF POWER BOILERS

Design of a vertical straight shell multitubular boiler

P

DS

N ¼ 64  10
3to 73 10
3 ð9-41gÞH

WHS

SHSWHS¼1

A ¼ Total area of steam segment

D ¼ Diameter of shell or drum

h ¼ Height of the segment to be occupied by steam

FIGURE 9-3 Areas of circular segments (Reproduced from G B Haven and G W Swett, The Design of Steam Boilers and

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DESIGN OF POWER BOILERS

Watertube boiler design

For mechanical properties of carbon and carbon

manganese steel plates, sections and angles for

marine boilers pressure vessels and welded machinery

and mechanical properties of steel plates for boilers

For properties of boilers

For evaporation of water, average rate of combustion

of fuels, and minimum rate of steam produced

Refer to Table 9-13Refer to Tables 9-14 to 9-16

TABLE 9-12

Mechanical properties of carbon and carbon manganese steel plates, sections, and angles steel for marine boilers,pressure vessels, and welded machinery

Elongation percentage min on

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DESIGN OF POWER BOILERS

For permissible strain rates of steam plant equipments

For water level requirements of boilers

For minimum allowable thickness of plates for boilers

For disengaging surface per horsepower

For heating boiler efficiency

Refer to Table 9-17Refer to Table 9-18Refer to Table 9-19Refer to Table 9-20Refer to Table 9-21TABLE 9-14

Evaporation kg (lb) of water per kg (lb) of fuel reduced to standard condition

Average rates of combustion [kg/m2(lb/ft2) of grate

surface per hour] draft 12.55 mm (1in) water column

Minimum kilograms (pounds) of steam per h per ft2of surface

Boiler heating surface

Water wall heating surface

Source: ASME Power Boiler Code Section I, 1983.

TABLE 9-17

Permissible strain rates for steam plant equipment

Strain rate

TABLE 9-18Water level requirementsa

Low water level 89 mm above surface of tubes for all diameters: distance between gauge cocks may be reduced

to a minimum of 75 mm

Low water level must be 75–125 mm above the water surface of the crown sheet; distance between gauge cocks is usually 75 mm for all diameters

a Low water level 890 mm above surface of tubes.

TABLE 9-19

Minimum allowable thickness of plates for boilers (all dimensions in mm)

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DESIGN OF POWER BOILERS

1 Haven, G B., and G W Swett, The Design of Steam Boilers and Pressure Vessels, John Wiley and Sons, Inc.,New York, 1923

2 ‘‘Rules for Construction of Power Boilers,’’ ASME Boiler and Pressure Vessel Code, Section I, 1983

3 ‘‘Rules for Construction of Pressure Vessels, ’’ ASME Boiler and Pressure Vessel Code, Section VIII, Division I,July 1, 1986

4 Code of Unfired Pressure Vessels, Bureau of Indian Standards, IS 2825, 1969, New Delhi, India

5 Nichols, R W., Pressure Vessel Codes and Standards, Elsevier Applied Science Publishing Ltd., Barking, Essex,England, 1987

6 Lingaiah, K., and B R Narayana Iyengar, Machine Design Data Handbook, Engineering College CooperativeSociety, Bangalore, India, 1962

7 Lingaiah, K., Machine Design Data Handbook, Vol II (SI and Customary Metric Units), Suma Publishers, galore, India, 1986

Ban-8 Lingaiah, K., Machine Design Data Handbook, (SI and U.S Customary Units), McGraw-Hill Publishing pany, New York, 1994

g acceleration due to gravity, m/s2(ft/s2)

ri inside radius, m (in)

ro outside radius, m (in)

h thickness of disk at radius r from the center of rotation, m (in)

h2 thickness of disk at radius r2from the center of rotation, m (in)

uniform tensile stress in case of a disk of uniform strength,

MPa (psi)

 tangential stress, MPa (psi)

r radial stress, MPa (psi)

z axial stress or longitudinal stress, MPa (psi)

 density of material of the disk, kg/m3(lbm/in3)

! angular speed of disk, rad/s

DISK OF UNIFORM STRENGTH

ROTATING AT ! rad=s (Fig 10-1)

The thickness of a disk of uniform strength at radius r

from center of rotation

The general expression for the radial stress of a

rotating disk of uniform thickness

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Source: MACHINE DESIGN DATABOOK

The general expression for the tangential stress of a

rotating disk of uniform thickness

The maximum values of stresses are at the center,

where r ¼ 0, and are equal to each other

(Fig 10-2)

The general expression for the radial stress of a

rotating disk of uniform thickness

The general expression for the tangential stress of a

rotating disk of uniform thickness

The maximum radial stress occurs at r2¼ rori

rðmaxÞ¼3þ 

8 !2ðro
riÞ2 ð10-7Þ

The maximum tangential stress occurs at inner

boundary where r ¼ ri

The tangential stress

The radial stress

The maximum stress occurs at the center

The axial strain in the z direction (ends free)

The axial stress under plane strain condition (ends

The tangential stress at any radius r

The radial stress at any radius r

The axial stress (ends free) at any radius r

The axial stress under plane strain conditions (ends

constrained) at any radius r

The maximum stress occurs at the inner surface where

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ROTATING DISKS AND CYLINDERS

The axial strain in the z direction (ends free)

The displacement u at any radius r of a thin hollow

rotating disk

SOLID THIN UNIFORM DISK ROTATING

po (Fig 10-3)

The radial stress at any radius r

The tangential stress at any radius r

The maximum radial stress at r ¼ 0

The maximum radial stress at r ¼ ro

The maximum tangential stress at r ¼ 0

The displacement u at any radius r

"z¼
!22E ðr2

ð3 þ Þð1
Þ8



r2o
1þ 3

3þ  r2

ð10-21Þ

rðmaxÞ¼
poþ !2



3þ 8

HOLLOW CYLINDER OF UNIFORM

EXTERNAL ( po) PRESSURES (Fig 10-4)

The general expression for the radial stress of a

hollow cylinder of uniform thickness rotating at

! rad/s under internal ð piÞ and external ð poÞ pressure

at any radius r

The general expression for the tangential or hoop

stress of a hollow cylinder of uniform thickness

rotating at! rad/s under internal ð piÞ and external

ð poÞ pressure at any radius r

The tangential or hoop stress in a hollow cylinder

rotating at! rad/s under poand piat r ¼ ri(Fig 10-4)

r¼ A
B

r2þ!28

; B ¼r2ir2oð pi
poÞ

r2

o
r2 i

þ!28



3
2

1


2r2oþ

þ!24

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ROTATING DISKS AND CYLINDERS

The tangential or hoop stress in a hollow cylinder

rotating at ! rad/s under po and pi at r ¼ ro (Fig

10-4)

The tangential stress in a cylinder rotating at! rad/s

at any radius r when subjected to internal pressure

ð piÞ only (Fig 10-5)

The tangential stress in a cylinder rotating at! rad/s

at any radius r when subject to external pressureð poÞ

only (Fig 10-6)

ROTATING THICK DISK AND CYLINDER

WITH UNIFORM THICKNESS SUBJECT

TO THERMAL STRESSES

The hoop or tangential stress in thick disk or cylinder

at any radius r rotating at! rad/s subject to pressure

poand pi

The radial stress in thick disk or cylinder at any radius

rrotating at! rad/s subject to pressure poand pi

þ!24

be found from boundary or initialconditions

 ¼ linear coefficient of thermal expansion, mm/8C(in/8F)

ROTATING LONG HOLLOW CYLINDER

WITH UNIFORM THICKNESS ROTATING

STRESS

The general expression for the radial stress in the

cylinder wall at any radius r when the temperature

distribution is symmetrical with respect to the axis

and constant along its length

The general expression for the tangential stress in the

cylinder wall at any radius r when the temperature

distribution is symmetrical with respect to the axis

and constant along its length

The general expression for the axial stress in the

cylinder wall at any radius r when the temperature

distribution is symmetrical with respect to the axis

and constant along its length

DEFLECTION OF A ROTATING DISK OF

UNIFORM THICKNESS IN RADIAL

DIRECTION WITH A CENTRAL CIRCULAR

CUTOUT

The tangential stress within elastic limit,
, in a

rotating disk of uniform thickness (Fig 10-7)

The expression for the inner deflectioni, of rotating

thin uniform thickness disk with centrally located

circular cut-out as per Stodalaa(Fig 10-7)

r¼ !28

d2

o
d2 i

¼E

i¼ 3:077  10
6

n1000

2ð7:5K2þ 5Þ ð10-38Þ

Aircraft; McGraw-Hill Publishing Company, New York, U.S.A Douglas C Greenwood, Editor, Engineering Data for Product Design, McGraw-Hill Publishing Company, New York, 1961.

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ROTATING DISKS AND CYLINDERS

FIGURE 10-7 Nomogram for radial deflection of rotating disks with constant thickness with a centrally located circular hole.

The expression for the outer deflectionoof rotating

thin uniform thickness disk with centrally located

circular cut-out as per Stodalaa(Fig 10-7)

The Nomogram can be used for steel, magnesium and aluminum since the modulus of elasticity E ¼ 29  106psi(200 MPa) for steel and Poisson’s ratio ¼ 1=3 The error involved in using this equation with E and  of steel foraluminum is about 0.5% and for magnesium is 2.5%

REFERENCES

1 Lingaiah, K., and B R Narayana Iyengar, Machine Design Data Handbook, Volume I (SI and CustomaryMetric Units), Suma Publishers, Bangalore, 1986

2 Lingaiah, K., Machine Design Data Handbook, McGraw-Hill Publishing Company, New York, 1994

3 Douglas C Greenwood, Engineering Data for Product Design, McGraw-Hill Publishing Company, New York,1961

o¼ 3:077  10
6

n1000

2ð1:5K2þ 7:5KÞ ð10-39Þwhere

K ¼ ro=ri

¼ tangential stress, psi

 ¼ iþ o¼ total deflection of disk, in

ri¼ inner radius of disk, in

ro¼ outer radius of disk, in

n ¼ speed, rpm

Aircraft; McGraw-Hill Publishing Company, New York, U.S.A Douglas C Greenwood, Editor, Engineering Data for Product Design, McGraw-Hill Publishing Company, New York, 1961.

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ROTATING DISKS AND CYLINDERS

A area of cross section, m2(in2)

d diameter of shaft, m (in)

diameter of cylinder, m (in)

E modulus of elasticity, GPa (Mpsi)

Ec modulus of elasticity of cast iron, GPa (Mpsi)

Es modulus of elasticity of steel, GPa (Mpsi)

F force, kN [lbf or tonf (pound force or tonne force)]

length of hub, m (in)

effective length of anchor, m (in)

L original length of slot, m (in)

Mt torque or twisting moment, N m (lbf in)

pc contact pressure MPa (psi)

coefficient of linear expansion, (m/m)/8C [(in/in)/8F]

 total change in diameter (interference), m (in)

d change in diameter, m (in)

s shaft

PRESS AND SHRINK FITS

Change in cylinder diameter due to contact

pressure

The change in diameter

The change in diameter of the inner member when

subjected to contact pressure pc(Fig 11-1)

The change in diameter of the outer member when

subjected to contact pressure pc(Fig 11-1)

The original difference in diameters of the two

cylinders when the material of the members is the

same

The total change in the diameters of hub and hollow

shaft due to contact pressure at their contact surface

when the material of the members is the same

d2

c
d2 i





ð11-2Þ

do¼pcdcE

do2þ d2 c

d2

o
d2 c

do2þ d2 c

d2

o
d2 c

þ 



þpcdcE

dc2þ d2 i

d2

c
d2 i

d2

s
d2 i

d2

o
d2 s

þ h

exactly ð11-5aÞ

 ¼ pcdc

dc2þ d2 i

Esðd2

c
d2

iÞþ

d2þ d2 c

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE

The shrinkage stress in the band

The contact pressure between cylinders at the surface

of contact when the material of both the cylinders is

1þ do24r2

1þdi24r2

do24r2
1

1
di24r2

ð11-12Þ


oi¼ pc

do2þ d2 c

d2

o
d2 c

ð11-14Þ


ii¼
2pcdc2

d2

c
d2 i

ð11-15Þ

The radial stress at inside diameter of outer cylinder

The semiempirical formula for tangential stress for

cast-iron hub on steel shaft

Timoshenko equation for contact pressure in case of

steel shaft on cast-iron hub

The allowable stress for brittle materials

INTERFERENCE FITS

Press

The axial force necessary to press shaft into hub under

an interface pressure pc

The approximate value of axial force to press steel

shaft into cast-iron hub with an interference

The approximate value of axial force to press steel

shaft in steel hub

Ec

¼ 3ð11-21aÞ

all¼su

n ¼ Ec½1 þ ðdc=doÞ2

dc½1:53 þ 0:47ðdc=doÞ2 ð11-21bÞ

where ¼ 0:085 to 0.125 for unlubricated surface

¼ 0:05 with special lubricants

F ¼ 4137  104ðdoþ 0:3dcÞl

doþ 6:33dc SI ð11-23aÞwhere do, dc, l and  in m, and F in N

F ¼ 6000ðdoþ 0:3dcÞl

doþ 6:33dc USCS ð11-23bÞwhere do, dc, l and  in in, and F in tonf

F ¼ 28:41  104ðd2

o
d2

cÞl

d2 o

SI ð11-24aÞwhere do, dc, l and  in m, and F in N

F ¼ 4120ðd2

o
d2

cÞl

d2 o

USCS ð11-24bÞwhere do, dc, l and  in in, and F in tonf

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE

The transmitted torque by a press fit or shrink fit

without slipping between the hub and shaft

The temperature t2in8C to which the shaft or shrink

link must be heated before assembly

Shrink links or anchors (Fig 11-3)

The average compression in the part of rim affected

according to C D Albert

The tensile stress in link

The total load on link

The compressive stress in rim

The original length of link

The necessary linear interference for shrink anchors

The force exerted by an anchor



rE

For letter symbols for tolerances, basic size deviation

and tolerance, clearance fit, transition fit, interference

fit

For press-fit between steel hub and shaft, cast-iron

hub and shaft and tensile stress in cast-iron hub in

press-fit allowance

TOLERANCES AND ALLOWANCES

The tolerance size is defined by its value followed by a

symbol composed of a letter (in some cases by two

letters) and a numerical value as

A fit is indicated by the basic size common to both

components followed by symbols corresponding to

each component, the hole being quoted first, as

For grades 5 to 16 tolerances have been determined in

terms of standard tolerance unit i in micrometers

(Refer to Table 11-l)

Values of standard tolerances corresponding to

grades 01, 0, and 1 are (values inmm for D in mm)

Refer to Figs 11-4 to 11-8

Refer to Figs 11-9 to 11-11

45 g7

45H8g7 or 45H8
g7 or 45

H8g7

Coefficient of friction, (for use between conical metallic surfaces)

Source: Courtesy J Bach, ‘‘Kegelreibungsverbindungen,’’ Zeitschrift Verein Deutscher Ingenieure, Vol 79, 1935.

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE

Upper deviations ( es) Lower deviation ( ei)

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE

TABLE 11-5

Clearance fits (Fig 11-6) (hole basis)

H 11 c 11

H 9 c 9

 normal

H 8 c 8

H 7 c 8

 fine

H 9 e 9



lubricated bearings requiring appreciable clearance; finer grades for high speeds, heavily loaded bearings such as turbogenerator and large electric motor bearings

H 8 e 8

H 7 e 8

 normal

H 7 e 7

H 6 e 7

 fine

H 6 g 6

H 6 g 5

 fine

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE

aStandard Tolerance Unit I (inmm)
0:004D þ 2:1 for D in mm Source: IS: 2101-1962.

TABLE 11-7

Transition and interference fits (hole basis)

Fit averaging virtually no clearance-recommended for location fits where a slight interference can be tolerated, with the object of eliminating vibration; used in clutch member keyed to shaft, gudgeon pin in piston bosses, hand wheel, and index disk on shaft

Fit averages a slight interference suitable for general tight-keying fits where accurate location and freedom from play are necessary; used for the cam holder, fitting bolt in reciprocating slide

Medium drive fit with easy dismantling for ferrous parts and light drive fit with easy dismantling for nonferrous parts assembly; pump impeller on shaft, small-end bush in connecting rod, pressed in bearing bush, sleeves, seating, etc.

H 7 s 6

 normal

Used for permanent or semipermanent assemblies of steel and iron members with considerable gripping force; for light alloys this gives a press fit; used in collars pressed on to shafts, valve seatings, cylinder liner in block, etc.

H 7 t 6



used in valve seat insert in cylinder head, etc.

TABLE 11-8

Preferred basic and design sizes

Linear dimensions (in mm)

Angular dimensions (in deg)

TABLE 11-9

Formulas for shaft and hole deviations (for sizes>500 to 3150 mm)

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METAL FITS, TOLERANCES, AND SURFACE TEXTURE