asme b1.11 1958

7/23/2019 ASME B1.11 1958

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ERRATA

ANSI B 1 . l l 958 (R1972 )

MICROSCOPE OBJ ECTIVE TH RE A D

JULY

1972)

Page

5,

Section

should

read,

American National Standard ANSI

B1.7-1965 (R1972)

Page 6, Section 4 should read, Angle

Deviation.

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7/23/2019 ASME B1.11 1958


A M E R I C A N

S T A N D A R D

Microscope

S B1.11-1 58

UDC 621.882.082:535.822:681.42

\

Society

of

Aufomotive Engineers

The American Society of Mechanical Engineers

. .

Society

of

Aufomotive Engineers

The American Society of Mechanical Engineers

r

? LSh L e d 6y

T H EA M E R I C A NS 0 C l E T . Y O F M E C H A N I C A L E N G I N E E R S

- ~ .

~ .~

..

~ ~

29 West 39th Street, New

York

18,

N.

Y.

~

.

-

=

__ . . ~ -

.

~ ~~ ~

. _

- r

- ~ .

~ .~

..

~ ~

29

West

39th Street, New

York

18, N. Y.

~

.

-

=

__ . . ~ -

.

~ ~~ ~



7/23/2019 ASME B1.11 1958


A S M E

B L - L Z 5 8

m

0 7 5 7 b 7 0

0037888 T W

Foreword

The standardizationof the microscope objective thread is one of the projects toward unification

of screw thread standards among inch-using countries. In Great Britain, the Royal Microscopical

Society had established standards for microscope objectives in 1858, based on the Whitworthscrew

thread system, which were subsequently used throughout the world. The history of this standard

is n the

Transactions

of the Society: 1858, p. 39; 1859, p. 92; 1896, pp. 389, 487; 1911, p. 175;

1915, p. 230; 1924, p. 266; and 1936, p. 377.

In.practice, American manufacturers of this thread have always employed modifications of the

Whitworth form because of their preference for flat crests, such modified threads being completely

interchangeable with the RMS threads. At the Conference on Unification of Engineering Stand-

ards held in Ottawa, 1945, the American Delegation resented ASA Paper B1/57 and A.O. Drawing

ED-95 giving limits of size for a truncated Whitwort thread. Since a thread form with rounded

crest is preferred in Great Britain for optical instruments, it was recommended that the itle of this

document be amended to read, “Proposed Permitted Truncation andTolerances for RMSThread.”

On the basis of this proposal a draf t of a proposed American Standard, dated April, 1948, was cir-

culated to the B1 Sectional Committee membership for comment. In conformity with comments

received, a revised draft, dated October, 1954, mas approved by Subcommittee No. 4 on Instrument

Screw Threads and subsequently submittedo theSectional Committee for approval. Final approval

as an American Standard was given on January

7,

1958, by ASA.

Any part

o

this standard may be quoted. Credit lines should read: “ Extracted rom America n

Standard Microscope Objective Threa d

(ASA

Bl.11-1958) with the permission of the publisher, The

American Society o Mechanical Engineers, 29 W. 39th St.,

N e w

York 18,

N. Y.’’

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7/23/2019 ASME B1.11 1958


A S M E B L - L L 5 8 m O 7 5 7 6 7 0 0 3 7 8 8 7 L

Officers of Sectional Committee on

Standardization and Unification of Screw Threads,

B1

Frank P. Tisch, Chairman

William H. Gourlie, Vice-Chairman

W.

C. Cadwell, Secretary

Personnel of Subcommittee No. 4

on

Instrument Screw Threads

E. W. Dresher, Chairman, Mgr,, QualityControl, Hathaw ay Instrum ent Division, Hamilton Watch Company,

J. C.

Burgbacher,

Engineer, Bulova Watch Co., Flushing, N. Y.

F. L. Calkins, Commander, W CXPS, Wright Air Development Center, Wr ight-P atterson Air Force Base, Ohio

J.

W. Evans,

Commander, WCLS

J3

Special Prod ucts Branch, Aircraft Labs., W right Air Development C enter

K .

E. Faiver,

Senior Design Engr., Olds Motor Div., General Motors Corp., Lansing, M ich.

R. F, Frye, Mgr., Materia ls Stds. Dept., Westinghouse Electric Corp., Eas t Pitts burg h, Pa.

I. H. Fullmer, Chief, Engineering Metrology Sec., National Bureau of Standards, Washington, D. C.

W. H.

Gourlie,

Stand ards Engr., T he Sheffield Corp., Dayton, Ohio

V.

C. Meigs, Engin eering Dept., A utonetics, a division of No rth Am erican Aviation, Inc., Bellflower, Calif.

D. R. Miller, 3521 36th St . , N.W., W ash ingt on, D. C.

J. H. Miller, Vice-Pres., Weston Electrical In stru me nt Corp., Newark, N. J.

D. V. Peroni, Commander, W CXPS , W right Air Development Center, W right-P atterson Air Force Base, Ohio

H.

W. Robb,

Manager, Company Standards, Engineering Services Div., General Electric Co., Schenectady,

N.

Y.

E. H. Schaeffer, Chief Engr., Elgin National Watch Co., Elgin, Ill.

M.

A.

Schultheis, St af f Engr., Systems Development L ab., Hughes Aircraft Co., Culver City, C alif.

C. E. Smart,

Works -Mgr., W, L. E. Gurley, Troy, N.

Y.

C. S.Tallman, Development Physicist, American Optical Co., Ins trum ent Div., Buffalo,

N.

Y.

S . B. Terry, Orient, L. I., N.

Y.

K. T.

Vande,

Chief Draftsman, Bausch Lomb Optical Co., Rochester,

N.

Y

D.

F. Viles,

President, Waltham Screw Co., Waltham, Mass.

P. F. Weber, Asst, to Pres., Kollsman Ins trum ent Corp., Elm hurst, Long Island, N.

Y.

Denver, Colorado

Wright-Patterson Air Force Base, Ohio



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7/23/2019 ASME B1.11 1958


A S M E ~ 1 . 1 1 , 8

m

0 7 5 7 b 7 0

0037870 8 m

American

Standard

MICROSCOPE

QBJECTPVE THREAD

GENERAL AND HISTORICAL

1 This standard covers the screw thread used

for mounting the objective assembly to the body

or lens turret of microscopes.

It

is based on, and

intended to be interchangeable with, the screw

thread introduced and adopted many years ago

by theRoyal Microscopical Society of Great

Britain, generally known as the RMS thread

and now almost universally accepted as the basic

standard for

.microscope

objectwemountings.

Formal recognltlon, however, has been extremely

limited.

2 Because of its British origin, the basic

thread possesses the British Standard Whitworth

form, havingn included angle of 55 and

rounded crests and roots. This same full Whit-

worth form salsoemployed as the design, or

maximum material, form by the British. The

present (American) standard, however, the design

thread form established in ASA1.6-1944,

American WarStandard for TruncatedWhit-

worth Threads, hasbeen adopted.

3 The pitchdiameter allowance and toler-

ances promulgated in June, 1924,for the

RMS

thread were subsequently applied bymost

American manufacturers

to

their truncated ver-

sions and found

to

be acceptable. Uniformity

of practicewith egard o he allowances and

tolerances for the other diameters never material-

ized.

4 Experiencehas established that he prin-

cipal attributes of a good fit for microscope

objective threads are:

a)

Adequate clearance to afford protection

against bin4ing due to the presence of

foreign par td es or minor thread crest

damage.

(b)

Sufficient depth of threadengagement

to assure security in the short lengths

of engagement c?mmonly encountered.

c)

Allowances for llmlted eccentricities

so

that centralization and squareness of

the objective arenot in%uencedby

such errors in manufacture.

5

The need for the above characteristics stems

principally from the inherent longevity of

optical

equipment and the repeated use to which objec-

tive threads are subjected. The measures neces-

sary

to

provide these properties precluded adop-

tion of the allowances and tolerances recom-

mended for threads of this pitch in the American

War Standard or Truncated Whitworth Threads,

ASA31.6-1944 (withdrawn, 1951). The more

significant departures from that standard are:

a)

A larger allowance on the pitchdiameter

of

the external thread.

b)

Smaller tolerances on the major diame-

ter of the external thread ndhe

minor diameter

of

the internal thread.

c)

The provision of allowancesn the

major and minoriameters of the exter-

nal thread.

The values established and further details regard-

ing them are given under Specifications.

6

Though utilized principally formicroscope

objective mountings, this screw thread is recom-

mended also for other optical assemblies of micro-

scopes and associated apparatus, such as photo-

micrographicequipment.

TERMINOLOGY

7

The nomenclature, definitions, andetter

symbols used n this standard are n conformance

with American Standard ASA B1.7-1949, Nomen-

clature, Definitions, and LetterSymbols for Screw

Threads.

SPECIFICATIONS

8 Basic Form of Thread.

The basic orm

of the hread for thisstandard is the British

Standard Whitworth form, Basic dimensions are

given in Table

.

9 Design Form of Thread. The design, or

maximum material, forms of both the external and

internal hreads conform

to

the American War

Standard for TruncatedWhitworthThreads,

ASAB1.6-1944 (withdrawn, 1951), The design

dimensions are given in Table

1.


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7/23/2019 ASME B1.11 1958


A S M E BL.33 5 8 m 0 7 5 7 6 7 0 0039893

T

AMERICAN ST ANDAR D.

TABLE 1 DEFINITIONS, FORMULAS, BASIC AND DESIGN DIMENSIONS

Property Symbol Formulaimension

BASIC

H READ

ORM

Half angle of thread” a ... 2 7 9 0 ’

Includedngle of thread” 2 a

e . .

55’00’

n

Pitch

Number of threads perncha 36

Height of fundamentalriangle

O 960491~ 0 .026680

Height of basichread h b

O. 4 0 3 2 7 ~ O 0178

Radius at crest and root of British Standard

Whitworth basic thread (not used) r

O

3 7 3 2 9 ~ 0.0038

DESIGN HREADORM

PH

iil

O 027778

Height

of

truncatedhitworthhread k hb- 0 . 5 6 6 4 1 0 ~. 0 1 5 7

Width of flat at crest F, 0 . 2 4 3 6 2 4 ~ O, 0068

Width of flat at root F, 0.166667p

O

M46

Basic truncation of crest from basicWhit-

worth form U O. 7 3 9 1 7 ~ O. 0205

BASIC

ND

DESIGNIZES

D

...

o

800

D n D

0.800

D - 2 U - G

O

7941

E D - 6 s

O. 822

E n

D-hb

O

7822

D - h b - G O 7804

D

- hb O .7644

K n

D ” 2 k O. 685

Minoriameter of extern al threadb K. D - 2 h s - G O. 626

Allowance at pitch (effective) diamete+ G

...

0.0018

2

All other dimensions are given in inches.

6 An allowance equal to that on the pitch diameter is also provided on the m ajor and minor diameters of the external thread

for additional clearance and centralizing.

c Allowance (minimum clearance) n pitch (effective) diameter is the same as on British RMS thread.

10 Lead

of

Thread.

The hread isof the

single (single-start) type.

11 Classification. There is established

herein only one class of thread which experience

has proved to be adequate to meet the demands

of the applications.

12 Nominal Sizes.

There is only one nomi-

nal size having a basic major diameter of 0.800

inch and a pitch of 0.027778 inch

36

threads per

inch).

13

Allowances.

Positive allowances -(mini-

mum clearances) are provided on the Itch, major,

and minordiameters of the external

t

‘ ead. The

allowanceon the pitch diameter is0.0018 inch,

the value established by the British Royal Micro-

scopical Society in 1924 and now widely regarded

as a basic requirement. The same allowance s

also applied on both the major and minor diame-

ters.

Where interchangeability with product having

full-form Whitworth threads is not required, the

allowances on the major and minor diameters of

the external thread are not necessary, since the

forms

a t

the root and crest

of

the truncated in-

ternal thread provide the desired clearances. In

such cases, either both limits or -only the maxi-

mum limit of the major and minoriameters may

be increased by heamount of the allowance.

Benefits are derived principally from changes in

the major diameter where increasing both limits

improves the depth

of

threadengagement, and

increasing only the maximum limit grants larger

manufacturing tolerance. However, unless such

deviations are specifically covered in purchase

negotiations,it

is

to be assumed that the threads

will be supplied in accordance with the tables in

this standard.

14

Tolerances.

In accordancewith tand-

ard practice, tolerances on the nternal hread

are applied in a plus direction from the basic

(also design) size and tolerances on the external

thread are applied in a minus direction from its

design (maximum material) size.

The pitch diameter tolerances for the external

and internal thread are the same andnclude both

lead and angle errors. They are derived from the

RMS “standard” of 1924 and are the sameas €or

the current British

RMS

hread.

The tolerance on themajordiameter

of

the

external thread and the tolerance on the minor

diameter of the internal thread are theminimum

values which experience has demonstrated to be

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7/23/2019 ASME B1.11 1958


MICROSCOPE

OBJECTIVE THREAD

practicable, Adequatedepth of thread engage-

ment is thereby assured.

All tolerances are given in Table 2

15 Lengths fEngagement.

The toler-

ances specified herein are applic?ble to lengths of

engagement anging from

/S

Inch to

a/8

inch

(approximately 15 to 50 per cent of the basic

diameter). Lengths of engagement exceeding

these limits are seldom employed and, conse-

quently, are not proyided or in thls s tandard.

For microscope objective assemblies the length

of engagementmost generally employed is /S

inch.

16 Limits of Size.

The limits of size for

both the external and internal thread are given

in Table 2 Their application is illustrated in

Fig. 1.

17 Thread Designation. This screw thread

shall be designated

on

engineering drawings, n

specifications, and

on

tools and gages by thesym-

bol AMO preceded by he basic major diameter

in inches and the number of threads per inch, as

given below:

O 800-36

AMO

TABLE

2

LIMITS

OF

SIZE AND TOLERANCESa

O

800- 36 AMO

Major Diameter Pitch Diameter Minor Diameter

Element

Max Min To1 Max Min To1 Max Min

To1

.External thread

0.7941.7911.0036

0.7804

0.7774.0030.7626

0.7552b

Internal thread

O

80% O.

000

: .7852.7822 0.0050 0.7715.7685.0030

a AU dimensions are given in inches.

Extreme minimum minor diameter produced by a new threading tool having

a

minimum flat of p/12 E 0,0023 nch).

C Extreme maximum major diameter produced by a new threading tool having

a

minimum flat of

p/20

E

0.0014

nch).

This minimum diameter is not con trolled by gages bu t by the form of the threading tool.

This

maximum diameter is not controlled by gagesbut by the form of the threading tool.



7/23/2019 ASME B1.11 1958


AMERICAN STANDARD

T

L

EXTERNA L THREAD

( RE

W

The Doff ed Line /ndicates

fheFu

o r m

Brjf ish Whjfworfh Threud on Which fhe

Royal Microscop icu/ Society Th read

s

Based

I N T E R N A L THREAD

NU

T

'/z

Major

Diameter

Af/owance

on Exitferna/ th re ad

FIG.

DISPOSITION

F

TOLBRANCBS,LLOWANCES,

ND

CREST LEARANCES

OR

AMO THRBAD



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7/23/2019 ASME B1.11 1958


M I C R O S C O P E O B J E C T I V E T H R E A D

Appendix

Recommended Gage D imensions of M icroscope bjective Thread

0 .800- 36 AMO

Dimension

Symbol Description Formula Dimension

“Go SETTING”THREADLUGAGE A-Go)

D,, ax Major diameter, maximum

D,Max O,

941

D,,

in Major diameter, minimum

’

D ag

0.0004

O. 937

E,, Max Pitch (effective) diameter, maximum

E. Max O

7804

E,, Min Pitch (effective) diameter, minimum

E,,

Max

.0002 O 7802

“NOT Go SETTING” HREADLUGAG E A-NOT GO )

D

in Major diameter, minimum D.Max

O

7941

D,, ax Major diameter, maximum

D

in

0.0004 O. 945

E,, Min Pitch (effective) diameter, minimum E. Min O, 774

Eo Max Pitch (effective) diameter, maximum

E,,

Min O

O002

O

7776

“Go”

THREAD

ING GA GE G-Go)

Eo

Max Pitch effective diameter, maximum

E,,

Max “Go” A Plug O. 804

E,, Min Pit ch effective] diame ter, minimum E,, Min “Go”

A

Plug O

7802

Kg Max Minor diameter, maximum D Min

hs O. 644

KOMin Minor diameter, minimum

KO

Max 0.0004

O.

640

“ N O T GO”

THREAD

ING GAGE %NOT GO)

Eo Min Pitc h (effective) diameter, minimum

Eo

Min “Not Go”

A

Plug o

7774

E,,

Max Pitch (effective) diameter, maximum

E,,

Max “Not Go” A Plug

O. 776

. K,Min

Minor diameter, minimum

E. Min /3.7681

K,, ax

Minor diameter, maximum

K O

Min 4- O o004 0.7685

“Go” THREAD

LUG

AGE C-Go)

D

in Major diameter, minimum

D

Min 0.8000

D,,

ax MaJor diameter, maximum D,, in 0.0004

0.8004

E,, Min Pitc h (effective) diameter, minimum E , Min O. 822

E,,

Max Pitch (effective) diameter, maximum Eo Min

0.0002

O.

824

“NOT Go” THREADLUGAG E C-NOT Go)

D

ax E , Max + p / 3

O.

945

Do

in

Do

ax O.OOO4 O 7941

E,, Max E,, Max 0.7852

E,, Min Eo Max

0.0002

O 7850

Tolerance in lea d.. ..........................................................

.0002

n.

Tolerance on half-angle of thread. ........................................... deg

20

min.

the rounded roots

of

which mill not pass

the

flat crest truncations of the gages. However, British gages, which are made to

NOTE : Ring and plug gages m ade in accordance with th e above dimensions are not suitable for checking British product,

check the full Whitworth form

of

thread, will accept American product.

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7/23/2019 ASME B1.11 1958


American Standard or Screw Threads and Threaded Parts

TITLE O F STANDARD

Microscope Objective Thread (B1.11-1958).

.............................................

Unified and American ScrewThreads for Screws, Bolts,Nuts, and Other Threaded PartsBl.1-

-1949) (Third Edition, published

in

1951).

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Screw Thread Gages and Gaging (B1.2-1951). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Aune Screw Threads (B1.5-1952).

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nomenclature, Definitions, andLetter Symbols for Screw Threads (B1.7--1949; reaffirmed

1953). . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . .

Stub Acme ScrewThreads (B1.8-1952) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Buttress ScrewThreads B1.9-1953). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Small Solid Rivets (B18.1-1955).

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Square and Hexagon olts and Nuts and Lagolts (B18.2-1955).

..........................

Socket HeadCap Screws and Socket Set Screws (B18.5-1954). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Large Rivets-1/2 In. Diameter and Larger (B18.4-1950; Reaffirmed 1957). . . . . . . . . . . . . . . . . .

Slotted and Recessed Head Wood Screws (B18.6.1-1956). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hexagon and Slotted Head Cap Screws, Square Head Set Screws, Slotted Headless Set Screws

(B18.6.2-1956) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pipe Threads B2.1-1945). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Round Unslotted Head olts (B18.5-1952). .............................................

Plow Bolts (B18.9-1950). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Track Bolts and Nuts B18.10-1952). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fire-Hose Coupling Screw Threads (B26-1925; reaffirmed 1953).

...........................

Hose CouplingScrew Threads (B33.1-1935; reaffirmed 1947).

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preferred Limits and Fits or Cylindrical Parts (B4.1-1955). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Quantity discounts as ollows:

In

lots of lO,ZO% of list;

50, 2.5 ;

100,30 .

PRICE

$1.OO

3.50

4.00

2.25

1.50

1.50

1.50

2.50

1

so

2.00

1.50

1

S O

1.50

1.00

1 O

1.50

1

S O

1.o0

1 o0

1.50

A binder is available or holding these standards. It holds tweenty- ve (2.5)pamphlets and gives every ad-

vantage

o

a bound book together with the added convenience which comes rom the ability to instant4 insert,

remove,

or

transpose sections of th e contents. Price 3.25Postpaid.

A

complete list

o

American Standards published

by

the American Society

of

Mechanical Engineers

06-

tainable u pon request.

A S M E members are entitled o a 20 per cent discount o a single copyo an y standard.


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asme b1.11 1958

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