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है”ह”ह

IS 8733 (1978): Tolerances for single start gear hobs [PGD32: Cutting tools]

UDC 821’914’8 : 621’833: 621’753’1 IS : 9733 - 1978

[s1

Indian Standard

1 I TOLERANCES FOR

SINGLE START GEAR HOBS

I. Scope - Covers the tolerances for single start gear hobs, suitable for modules 1 to 20, conform- ng to IS : 2535-1978 ‘ Basic rack and modules of cylindrical gears for general engineering and heavy 3ngineering ( second revision) ‘. The tolerances specified in the standard apply to all pressure angles.

2. Grades

!.l Gear hobs shall be classified into the following grades of accuracy:

Grade AA High precision ground hobs

Grade A Precision aground hobs

Grade B Commercial ground hobs

Grade C Precision ungiound hobs

Grade D Commercial unground hobs

2.2 Bearing surface length of bore for all grades shall be 66 percent except for Grade AA.

EXPLANATORY NOTE

In the preparation of this standard considerable assistance has been derived from DIN 3968- 1960 ‘ Toleranzen eingangiger Walzfraser fur Stirnrader mit Evolventenverzahnung (Tolerances for single-start hobs for involute spur gears ) ’ issued by Deutsches lnstitut fiir Normung.

Adopted 23 February 1978 Q August 1978, ISI I

~~~~~ ,id

INDIAN STANDARDS INSTITUTION MANAK BHAVAN, 2 BAHADUR SHAH ZAFAR MARG

NEW DELHI llOW2

3. Tolerances All tolerances in miciometres I 1 miciometre = 0’001 mm 1.

SI No.

Element to be

Checked

Illustration Symbol for

Tolerance

Grade Module

For Over Over Over Over Over Over Over 1 1 .

up to “;Yo ,;:o “ito “i3to u;to “lpGt0 1’6 2’5 4 6’3 10 16 20

AA H5t

A R5t Tolerance on

1 bore diameter * - B (d)*

H6t

C R6t

D l-W

2 Form tolerance of bore*

- All grades

One half the bore tolerance

Inteichange- All grades

According to IS : 6285-1971 ‘ Dimensions for interchangeability of milling cutters

3 able tole- and milling arbors with key drive ’ - - rance for keyway

AA 5 5 5 5 5 5 I 6 I 6

A 5 5 5 6 8 10 12 16 Radial 1

I

___ 1 ____ runout of hub

4 diameter with frP B 6 6 6 8 1 IO 12 16 20 respect to

-I..

_~_~~~ _ bore axis

C 10 IO 10 12 1 16 20 25 32

D Not defined

‘Bores with recess are to be treated as a single-diameter tnrough bore with regard to diameter and torm tolerances. For hobs of Grade AA, it is desirable that the bore should not be made with a recess.

TAccording to IS : 919-1963 ‘ Recommendations for limits and fits for engineering (revised) ‘.

( Continued )

All tolerances in miciometres ( 1 micrometie = 0’001 mm ).

-

?

--

_

_

-

-

-

-

-

-

Iti,

-

5

E:sombeen* Checked

Illustration Sw&bol

roleranct

fR8

Grade’

AA

Module

I -

I T Over

“pit0 1’6

3

Over

“;:o 2’5

3

3

4

6

Over 2’5

up to 4

3

5

6

10

Over

U&o 6.3

3

Over 6’3

up to 10

Over

“‘POW 16

Over

“$0 20

4 5

--

-.

--

5

5 8 3 10

6 10

.-

.-

10 12

_-

10 16 16 20

16 25 25 32

For 1

3

40

63

125

250

500

A 3 3

B 4

C 6

D

AA

10

10

fifx~;40yut

both faces with respect to bore axis

IO 12 16

12 16

20 25

___~

40 50

~__

80 100

160 200

10 20

32

25 32

A

B

40 50

--

30 100

12 16

25 32

Radial runotit on tooth tips with respect to bore axis

_-

6 frk 63

~I-

50 63 125 160 200

-1

250 315 400 100 125

P

All tolerances in micidmetres ( 1 miciometie = 0’001 mm 1.

Checked

Illustration Svmbal

Form and positional tolerance of cutting faces

DISTANCE U IS TM AMOUNT

BY WHICH DESIGN LINE

is INSTANT FROM PLANE OF HOB AXIS

(ZERO WHEN RAKE ANGLE IS O”)

I-_- CUTTING oEPTH----s(

TOOTH TIP\

TEST DIAGRAM

FIN

(Continued)

All tolerances in micrometies ( 1 miciometie = 0’001 mm ).

cn

Element to be

Chcrked

Illustration GYftyI Grade Module

Tolerance Foi - Over Ovei Ovrr Over Over Over

1 U;; go . uyo 6; O;83r I U~ot~ $0 . . 16 Ui,.

AA f 10 fl0 *12 zt 16 rt20 *225 f32 f4g

A *in fl6 f20 f25 f32 &40 zt 50 f63

Tolerance on -- 8 z;itlspacing

middle of fm* B =t25 f32 fm =tr5g zt63 &80 f 100 f 125

the tooth height

C f50 f63 *&I fig0 fl25 &NO zt2ocl f250

I

123C56789lfJ1112 D f 100 f 125 fl00 f2W f250 f315 f400 f 500

TEST DIAGRAM

AA 10 10 12 16. 20 25 32 40

Maximum tooth spacing

A 12 16 20 25 32 40 50 63

9 erroi bet- ween two ZERO flat B 25 32 40 50 63 80 100 125 adjacent -- -P teeth

C 50 63 30 100 125 130 200 250

1 2 3 1 5 6 7 3 9 10 1112 D

I 100 125 130 2M) 250

I 315 400 500

VN is the difference between the actual value and designed value of the gash spacing.

tTooth spacing error fuN is the actual difference in the spacing of two adjacent gashes.

( Continued )

All tolerances In miciometres f 1 micrometre = 0’001 mm 1.

SI No.

Element to be

Checked

Maximum cumulative tooth spac- ing error measured at half tooth height

--

11

Lead orror of gash over 100 mm hob length

illustration

1 2 3 L 5 6 7 8 9 10 1112

TEST DIAGRAM

roe mmI

f HN

S~~rbol

Tolerance

--

h*

fIiN

I Grade Module

Foi * Ovei Over Ovef OY’

Over Over Over 1 d; ul,!o . 6’3 10

2’6 ui:o usp; . Ur0to Upe’” ito

AA 20 20 25 32 40 50 63 80

A 25 32 40 50 63 80 100 125

B 50 63 80 100 125 160 200 210

C 100 125 160 260 250 315 400 500

D 2w 250 315 400 500 630 800 1000

AA

A

B

C

D

I

fW

f 70

f 100

f140

fnao

*The tolerance Ft~ is referred to the total pitch eiror, that is to say that the krgest Cumulative pitch error measured on the hob tested.

( COntifWsd J

All tolerances in miciometres ( 1 micrometre = 0’001 mm 1.

Element to be

Checked

-

1 -

s,,y1

Tolerance

Module Illustration drade

T

For a Over Over 1 Oit’ Over Over Over

up to u;to $0 4 6’3 16

Over

u;to

18

32

63

125

- 50

-50

-160

- 320

-320

f12

*20

f40

f60

6 6

10 12

20 25 --

40 50

. .

_

~ _

-

__

AA _-

_-

.-

.-

A ,-

Permissible error over the straight flank from ;z;iesign

B FfS

fi

_‘_

I - C

D

AA

Not defined

-20 - 25 -32 - 40

-36 -40 - 50 - 63

- 71 -60 - 100 - 125

-146 - 160 -200 -250

- 140 - 160 - 200 - 250

f5 f6 &6 f 10

f9 *lo f12 f 16

fl6 lt2o 525 rt 32

f36 rt40 f50 . +63

- 16

-25

-56

-106

- 100

f4

f6

f12

f25

f50

- 16 - 16

-28 - 32

-56 -63

- 112 - 125

-112 - 125

f4 f4

&I7 f8

fl4 ft6

f28 f 32

556 f63

A Tolerance on tooth thick- ness on the pitch cylinder

B

C

D

=fHF

AA

A

Hob lead from cutting edge to cutt- ing edge in Lyh”,i;ction

fHF B

where HN = lead of gashes, H = hob lead ( helix), and i = number of gashes or tooth rows. The sign in the parentheses is plus ( +) if gash lead and the hob lead are in the opposite direction, and negative ( - ) If they are in the same direction

C

I -IpI I ! f)

f71 1 zt60 1 fl60 / f125 / &I60 D

( Continuea

Ipa- . .

All tolerances in micrometres ( 1. micrometre = 0’001 mm ).

IE!. Element to be

Chebked

Grade Module Symbol for

rolerance

Illustration -

For 1

Over Over

&to L&s,0 1’6 2’5

AA 6 6 6

10 11

22

12

20

40

25

45 50

D 80 90 100 112 125

AA f4 *4

.-

_ *4

-

_.

-

_ -

--

-

--

--

--

-

-

Over

U&o 6’3

Over

u6p3t 0 10

10 12

16 20

28 32 40

56 63 80

160

*5 f6

ItI9

*20

f 49

-.

_-

-_

-

zt:25 f32 f40

* 50 f 63 rt80

-

_.

-_

-

Over

u;to

Over 16

up to 20

14 18

25 32

50

190

200

-

-_

- .

__

- _

. -

-i

63

125

250

f IO f12

3116 f20

__

Over

“;5to 4

8

14

f9

518

f 36

n.HN.H

ilHN=H) =FHF

t-l

Hob lead in ;yhf;rtion

between any two cutting edges on the same thread

15 FHP where

HN = Lead of gashes,

H = hob lead ( helix ), i = number of gashes or tooth rows, and n = number of cutting edges on which the

measurement is made. The sign in the parentheses is plus (+ ) if gash lead and the hob lead are in the opposite direction, and negative ( - ) if they are in the same direction

rt6 &7 f8

fl2 f 14 f ‘6

f25 f 28 d.132

A

B Individual base pitch error

16 fe

C where

te = base pitch, ahd

i = number of gashes

D Not defined

( Continued)

All toleiances in micrometres ( 1 micromktre = 0’001 mm ).

Element to be

Checked

Illustration Grade Module SytT,bol

Tolerance

For 1

Over 1

up to 1’6

Over

“iat 2’5

Over .

u’,:o 4

Over

u;io

Over

“ito

Over

u;io

Over

uyo

16

Cumulative base pitch error within the contact region

AA 8 8 8 10 12 25

14 16 25 32 40

80

160

18

36 17

TEST DIAGRAM -

18

Diametei tolerance over hob length

-

28 32 63

125

25

50 56 63 II 80 100

D Not defined

--

20

-

_-

.-

.-

-

25 32 AA 8 8

___~

i0 12

20 25

40 50

12

20

40

80

Not defined

10

16

32

63

16

25

50

100

A 50

100

32

63

40

80

C 125

---

160 200

D