Nut and bolt loading curves.

UNCLASSIFIED ORNL-578

AL RESEARCH LIBRARY

UMENT COLLECT-3ON

NUT AND BOLT LOADING CURVES

CENTRAL RESEARCH LIBRARY

DOCUMENT COLLECTION

LIBRARY LOAN COPY

DO NOT TRANSFER TO ANOTHER PERSON

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OAK RIDGE NATIONAL LABORATORYOPERATED BY

CARBIDE AND CARBON CHEMICALS DIVISIONUNION CARBIDE AND CARBON CORPORATION

ITTW

POST OFFICE BOX P

OAK RIDQE, TENNESSEE

UNCLASSIFIED

UNCLASSIFIED

Contract No. W-7^05, eng 26

OBNL-578

This document consista 55pages.m

n"ry__/- of 1fr* Series A.

TECHNICAL DIVISIONBnginoering Development Section

HUT AND BOLT LOADING CURTIS

C. P. Coughlen

DATE ISSUIDsFEB 151950

OAK RIDGE NATIONAL LABORATORYo-o@rated by

CARBIDE AND CARBON CHEMICALS DIVISIONUnion Carbide and Carbon Corporation

Post Office Box P

Oak Ridge, Tennessee

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- 3 -

TABLE OF CONTENTS

1.0 ABSTRACT .....

2.0 INTRODUCTION .

3.0 TEST PROCEDURE

k.O TEST DATA ..r .

5.0 DISCUSSION OF RESULTS

APPENDIX

I TABLE OF OBVIOUS DEFECTS.........................

II SHIFT IN LOADING CURVE ON SECOND RUN-DOWN OF NUT,

III EXCERPT FROM MEMO UNDER DATE OF 23 MARCH, 19^9BIB. VAN WINKLE

ORHL-578

Page

k

k

5

6

*7

*9

50

51

- k - ORNL-578

1.0 ABSTRACT

Tests of nut and bolt sets were made wherein were measured the bolt

loads resulting from controlled torques applied to the nuts. Torques were

applied using calibrated torque wrenches. Loads were measured by a

Tate-Emory Universal Testing Machine in which the specimens were mounted.

Metals of construction, bolt sizes (l/2" to 1 l/8") and thread

surface conditions were varied.

Normalized curves are presented with little comment, the data being

considered too scanty to permit firm conclusions.

As appendices are (I) a table of comments on certain irregularities

noted during the test work, (II) a table listing qualitatively the shift

in the loading curves on the second run-down, and (ill) a reprint of an

analysis of the data (by R. Van Winkle) that was included in a memorandum

of very limited distribution. The analysis includes some additional data

developed by Van Winkle.

2.0 INTRODUCTION

A specific design under consideration specified the use of unlubricated

stainless steel nuts and bolts of sizes within the range of l/2M to 1 l/8w

(standard). Concern was expressed that maintenance operations would be

complicated by the 'freezing' of nuts on bolts and studs.

The subject investigation was undertaken in an effort to develop

information that would serve as a basis of prediction of maintenance

difficulties and aa a basis for specifying bolting materials.

~5 - ORNL-578

2.0 INTRODUCTION (Cont'd)

Time being available at the inception of the work, the decision was

made to expand the tests somewhat, to include the use of some non-stainless

materials and the effect of conditions not called for by the above mentioned

design.

3.0 TEST PROCEDURES

Special holders were constructed for use with a Tate-lmory Universal

Testing Machine. The holders consisted of a shaft about lh inches long

and 3 inches in diameter which attached to a wedge block that locked the

shaft into the bottom movable platten. The bolt head was locked by set

screws into a heavy duty cap that screwed onto the upper end of the shaft.

The bolt extended through the cap and thence through a heavy duty plate which

rested on the upper platten of the machine, A lubricated washer was usually

used. The nut was run down until the nut threads were full, the platten

adjusted to give a nominal load reading on the testing machine, and the

bolts further loaded by hand operated torque wrenches.

The torque wrenches used varied in size from 50 ft-lbs. maximum to 420

ft-lbs. maximum. Each was calibrated by loading th® wench with lead brick

and shot.

The bolt loads at a number of applied torques were recorded.

- 6 - ORNL-578

3.0 TEST PROCEDURES (Cont'd)

Test groups normally consisted of nine bolt-nut pairs each. These

were randomly separated into three sub-groups; (1) for testing in the

'as received' condition, (2) for testing in the 'degreased' condition

(2 washes of carbon tetrachloride), and (3) for testing in the 'greased'

condition. For the latter condition the Testing Machine threads were

robbed of a little grease.

k.O TEST DATA

The data are presented as normalized mean curves. No single curve,

with but one exception, was developed from more than three individual run

curves. Anomalies are present and will be discussed briefly later.

In all cases, the abscissa Is 'foot-pounds' of applied torque and the

ordinate is the resulting load in thousands of pounds (kips).

The curves are grouped in three ways. First, the metal pairs and

surface conditions are held constant for each plot with the curve family

representing different sizes. Second the size and surface condition are

specified with the family of curves describing different metal pairs.

Third, the metal pairs and the size are specified resulting in a curve

family of conditions of surface.

The shifts in the loading curves and successive run-downs of the nut

are presented in appendix II.

COI

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a

•&

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o

- 7 -

100 150 200 250

Torque Applied to Nut-Ft,-Lbs,

COi

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id

+»

o

r-Hm

o

8 -

FIGURE 4.1.1.2

303 S. S. Nut303 S. S. Bolt

"IBB 15o—' ' 250' 255"

Torque Applied to Nut-Ft-Lbs.

Condition - Degreased

CO

oHI

M

CD

o

(15

O

20-

- 9

FIGURE 4.1.1,3

303 S. S. Nut

303 S. S. Bolt

100 150 200 250

Torque Applied to Nut-Ft. Lbs.

Condition - Greased

CO

oH

M

CO

hi

i

•d

•P

o

•poE-l

10 -

100 150 200 250


COi

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20

TlJUL —

FIGURE 4.1.2.2

303 S. S. Nut304 S. S. Bolt Condition- Degreased


COi

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<?•d

3

i-4

O

20

- 12 -

'V'"'%/«Si^:SjAl^

FIGURE 4,1,2.3303 S. S. Nut

304 S. S. Bolt Condition - Greased

Torque Applied to Nut-Ft-Lbs,

CO

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•pHIO

•po64

^-M,-

/

//

FIGURE 4 .'1.3 «1

Condition - As Received

Curve 1 - Steel Nut

304 S.S. Bolt

Curve 2 - Steel Nut

303 S.S. Bolt

3/4"

3/4w

50 ioo 150 . 200 250

Torque Applied to Nut-Ft.-Lbs.

300 350

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20

15

14


Curve 1 - Steel Nut" 304 S.S. Bolt - 3/4'

Curve 2 - Steel Nut~ 303 S.S.Bolt - 3/4"

50

Curve 3 - Steel Hut304 S.S. Bolt - 1

3.00 150 200 250Torque Applied to Nut-Ft.-Lbs,

300 350

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J33

hiI

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oPI

o64

50

15

FIGURE 4.1.3.3

Condition - Greased

Curve 1 - Steel Nut~ 304 S.S. Bolt - 3/4"

Steel Nut

303 S.S. Bolt - 3/4B

Curve 3 - Steel Nut~ 304 S.S. Bolt - 1 1/8"

100 150 200 250Torque Applied to Nut-Ft-Lbs.

300 350 400

COI

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a

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+»Q

64

20

16

FIGURE 4.1.4.1

Carbon Steel Bolt Condition- As ReceivedCarbbn Steel Nut

25 50 75 100 150 200Torque Applied to Nut-Ft-Lbs.

300 350

CO1

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M

a

HIO

o64

20

50

17

FIGURE 4.1.4.2

Carbon Steel Bolt Condition - Degreased

Carbon Steel Nut

100 150 200 250


300 350

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so

•po64

- 18

100 150 200 250


co

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M

©

•d.

a

H

•864

To~ 50 b6 TO"


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r-J

£

64

40 50 6jd~ 70Ttarque Applied to Nut- Ft-Lbs.

POj

•aM

a•d

o

HS3•P

//

S"

/

/

*» $°

' j£$•>

FIGURE 4.2.1.3

Comparison of Various Metal Pairsat 1/2w Size

Condition - Greased

J0 1() 2 0 3<3 40 5«5 60 7<5 8 0 90 100


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to

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8hi

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64

22 -

16—

ill

•

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10

c#X

^ 3: ^*r

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^^^ FIGURE 4.2.2.1

Comparison of Various Metal Pairsat 5/8" Size


6

/ &

k-4

2

— /

1 1 1 11', 10 ?ni1 | _L 1 1 I | 1 | , jj i

0 2 0 4(3 £ 0 8<3 1 00 u 20 1*0 L60 180 200

Torque Applied to Nut-Ft.-Lbs

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14

12

10

8

23 -

C onTnArlaon

FIGURE k

nf TTnT"4 mis

-.2.2.2

Ma+.a 1 Pn 1 vq

at 5/8" Size


s

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—

—

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• -

—

^ ^| , ! ^ , _u i 1 1

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40 60 80 100 120 140


20 160 180 200 220

24

00 100 120

Torque Applied to Hut-Ft-Lbs.

220

CO

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(0-po64

25 -

St-St

St-303

St-304

303-303303-304

°fl—

^6FIGURE 4.2.3.1

Comparison of Various Metal Pairs

at 3/4" Size


24

'tHH '

2U

18

—

•

16

14

-"

12

1 0

—

^ — •„ ^

—

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8

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0 >* ff fi& &**"

1 I 1 |_i__l_ | | 1 1 | | 1 1

0 10 20 30 40 50 60 70 80 90 100 120 130 140 150 160 170 180 190 200 210 220


co

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a 20

«

n ltthi

•pHI 16O

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64

12

40

26 -

80 100 120 140


FIGURE 4.2.3.2

Comparison of Various Metal Pairsat 3/4" Size

Condition- Degreased

200 220 240

80 100 120


27 -

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or-4

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ao

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13

12

11

10

9

8

FIGURE 4.2.4.2

Comparison of Various Metal Pairsat 1 1/8" Size

Condition- Degreased

- 28


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29

200 300


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3o

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30 -

CO1

10 -

S ?

m

a1

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3o«

1-4

i

FIGURE 4.3.1.2

Hut- 303 S.S.Bolt- 303 S.S.

Size 5/8"

31

*5o" 80 100


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8

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a)

g

"Bq 120 160 200Torque Applied to Nut-Ft-Lbs.

32 -

FIGURE 4.3.2.1

304 S. S, Nut304 S. S. Bolt

Size 1 1/8"

Curve 1 - As ReceivedCurve f^A - Greased-Shipment 1Curve 2-B - Greased- Shipment 2Curve 3_ - Degreased

- 33 -

150 200 250 300Torque Applied to Nut-Ft-Lbs.

Lll 1 1 I 1.450

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8

opq

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34 -


To

tal

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36 -

80 120 160 200

Torque Applied to Hut-Ft-Lbs,

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10

FIGURE 4.3.3=4

Nut - 303 S.SBolt - 304 S.S

37 -

TSC ISo SOO 240"


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- 38 -

As Racelved

/ Degreased

FIGURE 4.3.4.1'

316S. S. -*-»- Hut304 S. S. -*— Bolt

Conditions as labelled.

Size 5/8'

200

Torque Applied to Mut-Ft-Lbs.

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64

- 39 -

80 120 160 200 240


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10

8

40 -

—

/

I-

—

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fa1 ISi

—

—

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•

—

—

II—

/ /

/ £f JS/

—

—

—

FIGURE 4:3.5.1h

Hut - Carbon Steel

Bolt - 304 S.S.

Size - 3/4"

—

—

—

—

—

— M J

mi

40 80 120 160 200 240Torque Applied to Nut-Ft-Lbs.

COI

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CD

a

•d<aohi

HI

$

150 200 250 300Torque Applied to Hut-Ft-Lbs.

co«

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Mo

CO

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64

42 -

ic

-

FIGURE 4.3.6.1

8Nut - Carbon Steel

Bolt - Carbon Steel

Size - 1/2"7

6

~

4

5

<*>

•

31

*&y

2

1

0 sK J 1 1 | | 1,

j_ • ii 1 , | 1 L

Ci 1 0 2/>'' 3 0 Vc> 5 0 o£) 701 8o


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43 -

T«j "6^ 80


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- 44

-

FIGURE 4.3.6.3 t

20— Nut - Carbon Steel

/

Bolt- Carbon Steel //

Size - 3/4"18

—

/

/

-/

/

1.6 / f

— / /

14 / •*/ /

/

55 /

12w

t/—

4V

in

8

6

4

J

olr\ 1 l I 1 | 1 i 1 \ | ! | I 1 10 4 ) 80 ll20 16 0 2(30 240 2(50


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45

20

18

16

FIGURE 4,3.6.4

Hut - Carbon Steel

Bolt - Carbon Steel

Size - 1"

/

/

/ '

/ j.

/

/14

TO

—

J/i/*v/Jo/

V

//

/

10

^

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7

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8

6

—

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0 5 0 1C0 1 ^o 2C)0 250 3C)0 350 \^00


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Tin6 ! /

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//

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5

—

— i

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k

—

—

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Everdur NutTSvnyAur' Bolt

3

—

Conditions as labelled.

Size 1/2"/

1

12

—

FIGUBE M.7.1

—

J

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1

i

1

1,—

/ /

0 K\ 1 >l 1

1

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, ,4—J—

1*00 10 20 30 ko 50 6o 70 80 90 100 120Torque Applied to Hut-Ft-Lbs.

_ kj - ORNL-578

5.0 DISCUSSION OF RESULTS

The number of data available for each curve are statistically

inadequate to permit any claims that they may be used as design bases

unless a wide uncertainty is allowed. Lack of manpower, economically

spendable, forced the investigation into a suspended category. The

preservation and dissemination of the data obtained to date is the only

excuse for this report at this time. At some later date, additional effort

may be expended to develop sufficient additional data so that the sum total

then available may be statistically adequate for firm conclusions.

The curves may be considered to describe the loading characteristics

of only the test groups.

Qualitatively, considerable can be said. Orders of bolts and nuts,

manufactured supposedly to meet purchase order specifications, were found to

be little better than surprise packages. Material specifications were not

met in over 50$ of the orders. The specified No. 2 fits were often doubtful.

Further, careful examination of a test group usually led to the

conclusion that all members of the group were structurally identical with

comparable thread surfaces. Yet quite divergent results were often obtained.

Re-loading results were often unpredictable. Improvements resulted when

degradations were expected, and vice versa. Further, the entire range of

•degradation through no change to improvement' was found in three-member

test groups in more than one instance.

- 48 - ORNL-578

5.0 DISCUSSION OF RESULTS (Cont'd)

Speculation Is in order as to the effects of various variables, i.e.

the condition of the bolt machine cutters, the disposition of the bolt

machine operator, etc. It is suspected that variables such as these play

Important parts in determining the loading of any given nut-bolt set.

To sum - the data are inadequate but are here presented as a matter

of record to satisfy numerous requests that they be so presented.

- 49 - ORNL-578

APPENDIX I

TABLE OF OBVIOUS DEFECTS

1/2" Hut 303 S. S. ———————— in degreased condition, threads ofBolt 303 S. S. both nut and bolt galled badly.

5/8" Hut 303 S. S. — .—.——__ in degreased condition, two setsBolt 304 S. S, froze after second run-down.

1 1/8" Nut 304 S. S. — -- In degreased condition, two setsBolt 304 S. S, froze after second run-down. In

all conditions, threads were badlygalled,

- 50

APPENDIX II

SHIFT IN LOADING CURVE ON SECOND HUH-DOHH OF HUT

ORNL-578

Result of Second Run-Down

Hut Bolt As

Condition

Material Material Size Received Degreased Greased

303 S. S.303 S. S.303 S. S.303 S. S.

304 S. S.304 S. S.304 S. S.304 S. S.

1/2"5/8"3/4"7/8"

AD

AD

AI

SD

AD

AD

WV

SD

V

LC

LC

303 S. S.303 S. S.303 S. S.

303 S. S.303 S. S.303 S. S.

1/2"5/8"3/4"

SD

AD

AD to LC

SD

AD

V

SD

SI

LC

304 S. S. 304 S. S, 1 1/8" AD to V WV AI to LC

C. Steel

C. Steel

0. Steel

C. Steel

C. Steel

C. Steel

C. Steel

C. Steel

1/2"5/8"3/4"

1"

AD

SI

LC

WV

AD

AD

AD

AD

AI

AI

V

SD

316 S, S. 304 S. S. 5/8" AD LC AI

Everdur Everdur 1/2" SD AD V

Steel

Steel

304 S. S.304 S. S.

3/4"1 1/8"

AD SD

SD

AI

LC

Steel

Legend

AD

SD

LC

SI

AI

V

WV

303 S. S. 3/4" SI

Appreciable degradation of loading curve.Slight degradation of loading curve.Little change in loading curve.Slight improvement of loading curve.Appreciable improvement of loading curve.Variable change.Widely variable change.

SI

- 51 -

APPENDIX III

Excerpt from memorandum under date of 23 March, 1949, by R. Van Winkle.

"According to the piping handbook, an initial bolt stress of 30,000

to 60,000 psi to set the gasket in place is common practice. The initial

tension secured in bolting depends on the method of control, if any, used

in tightening the bolts. Experienced pipe fitters usually tighten the bolts

in high pressure flanges to give a bolt tension of approximately 60,000 pel

with raised-face Joints. In the case of ring-type Joints, a bolt tension

of 30,000 psi has been found adequate. Bolt tension may be controlled to

some extent by use of torque wrenches adjusted to permit application of only

sufficient turning effort to secure the desired bolt stress.

The turning required to secure bolt stresses of 30,000 and 60,000 pel

with different size alloy-steel bolts threaded in accordance with the

American Standard Screw Threads is given in Table I.

TABLE I

Nominal

Diameter

of Bolt,

Number of

Threads

per

Area at root

of

Thread

STRESS

30,000 Ib/sq.in. 60,000 lb/sq.in.Torque Force per Torque Force per

Inches Inch Sq„ Inches ft-lbs. bolt,lbs. ft^lbs. bolt,lbs.

1/2 13 0.126 30 3780 60 75605/8 11 0.202 60 6060 120 12,320

3/4 10 0.302 100 9060 200 18,1207/8 9 0.419 160 12,570 320 25,1401 8 0.551 245 16,530 490 33,060

1-1/8 8 0,728 355 21,840 710 43,6801-1/4 8 0.929 500 37,870 1000 55,740

- 52 - ORNL-578

APPirogjEII (Cont'd)

This table is based on tests conducted by Crane Company and represents

results obtained with well-lubricated thread® and bearing surfaces. Tests

with no lubricant on threads aad bearing surfaces showed an increase of

almost 100$ in the torque required to secure a given bolt stress.

The use of stainless steel bolts and nuts for bolting components

together presents the problem of obtaining adequate bolt tension without

galling the threads.

Careful tests conducted by C» P, Coughlen"s group indicate that in no

case could stainless steel bolts and nuts fe® tightened sufficiently to give

bolt stresses as high as 60,000 psi without serious galling of the threads.

Table 2 shows a summary of the torques that war® required to produce a stress

of 30,000 psi in 1/2", 5/8% 3/4", 7/8'B and l-l/8w stainless steel bolts and

nuts. Comparison of Table 2 with Table 1 shows that stainless steel bolts

and nuts require almost 100$ more torque for a given bolt stress than do

the alloy steel nuts and bolts tested by the Gran© Company,

In order to circumvent the problem of tte"@a& galling by the use of 303

stainless steel nut® on 303 stainless steel bolts, it has been proposed to

use hardened chrome steel nuts on 303 bolts, which are two dissimilar

metals.

53

APPEHDH III (Cont'd]

TABLE 2

COUGHLEH DATA

ORHL-578

Bolt

Diameter

Bolt

Material

Hut

Material Treatment

30,000 psi Stress 60,000 psi Stress

Torqueft .lb.

Force perbolt,lb.

Torqueft.lb.

Force perbolt,lb.

1/2--l/2«l/2M

303303303

303303303

As Rec"d

DegreasedGreased

48-6052-62

62

378037803780 -

756075607560

1/2"1/2"

.1/2"

304304 ,304

303303303

As Rec'dGreased

Degreased

40-4-743-4755-58

378037803780 -

756075607560

5/8-5/8-5/8"

303303303

303303303

As Rec'dDegreasedOreased

106-118115-143115-119

606060606060

- 12,120w

It

5/8"5/8"5/8"

304304304

303303303

As Rec'd

DegreasedCreased

118-134166-210

92-93

606060606060 -

»

It

w

3/4"3/4"3/4"

303303303

303303303

As Rec'd

DegreasedGreased

191-202200-223169-183

906090609060

- 18,120

18,120

3/4"3/4"3/4"

304304304

303303303

As Rec'dDegreasedGreased

200-220*

2l8-230f172-175

906090609060

- 18,120«

n

3/4"3/4"3/4"

303303303

Steel

Steel

Steel

As Rec'd

DegreasedGreased

134-140205135-131

906090609060

-

18,120n

M

7/8"7/8"

304304

303303

As Rec'd

Degreased(240)1(240 )X

12,57012,570 -

25,140

1-1/8"1-1/8"

304304

Steel

Steel

DegreasedGreased

440440

21,84021,840 -

- 54 -

APPEHDH III (Cont'd)

ORHL-578

Tests were performed with a torque wrench to determine the effect of

heavy torques on the 303 stainless steel bolt threads using hardened chrome

steel nuts. Ho thread damage was observed in any of the tests. Table 3 is

a summary of the tests.

TABLE 3

Bolt

Diameter

1/2"*1/2"7/8"7/8"

1"

Torqueft-lb.

100-140120

240-340305-400450-500

Estimated

Bolt Load

9000-12,00011^,00014,000-20,00018,000-23,00022,000-25,000

Estimated

Stress

70,000-95,00067,00033,000-48,00043,000-55,00040,000-45,000

* Twisted bolt in two using a torque of 175 ft-lbs. Threadswere undamaged and the nut ran freely on and off the threads.

In Table 3, the bolt loads were estimated by combining Coughlen's

experience with the results given in Table 1. For instance, in Table 2,

using a steel nut on a 303 stainless steel 3/4" bolt (as received condition),

a torque of approximately 134-140 ft-lbs. was required to give a bolt load

of 9060 pounds, while in Table 1, for the same bolt size, a torque of only

100 ft-lbs. was required. Thus, about 1.35 times as much torque needs to be

applied to a steel nut on a stainless steel bolt than on the materials used

in the test of Table 1.

Estimated bolt load = Force per bolt (Table 1) x ^1^1 Torque x1735Estimated stress =

Estimated bolt load

- 55 - 6RHL-578

APPEHDIX III (Cont'd)

According to these assumptions, then, the required torques to produce

30,000 psi and 60,000 psi are given in Table 4.

TABLE 4

ESTIMATED TORQUES FOR VARIOUS BOLT DIAMETERS

Bolt

Diameter Bolt Hut

STRjess

30,000 psi. 60,000 psi.Torque Bolt Torque Bolt

Inch Material Material ft.lbs. Load ft.lbs. Load

1/2 303 S.S. Hardened 40 3780 80 75605/8 n

Chrome 81 6060 162 12,1203/4 it

Steel 135 9060 270 18,1207/8 « « 216 12,570 432 25,140

1it « 330 16,530 660 33,060

'Date

/gd

Nut and bolt loading curves.

Documents

Transcript of Nut and bolt loading curves.