In  such  a  thread  the  pitch,  the
depth,  and  the.  radius  are  found
by  the  following  formulas :

1"


WHITWORTH    STANDARD
THREAD

(7,  depth;  p,  pitch;  r,  radius  of
curvature


Pitch    =


Depth  =


Radius  =


number  of  threads  to  1"

0.6403"

number  of  threads  to  1"

0.1373"
number  of  threads  to  1"


=  0.6403  x  pitch


=  0.1373  x  pitch


The  following  table  shows  the  standard  number  of  threads
per  inch  for  Whitworth  threads  of  the  following  diameters:


Do

T

DO

T

D9

T

A,

r

A"

60

A"

12

u"

7

111"

U

£

48

f

11

1A

7

2

*J

i

40

H

11

if

6

2i

*1

A

32

3
?

10

i*

6

2J

4

A

24

«

10

H

6

2i

4

&

24

I

9

1A

6

2|

3^

i

20

if

9

if

5

3

»i

A

18

1

8

itt

5

»i

3i

1

16

1A

8

if

5

3^

31

A

14

H

7

iH

5

3^

3

*

12

iA

7

ii

H

4

3

In  this  table  D0  stands  for  the  diameter  of  the  screw  and  T  for
the  number  of  threads  per  inch.
WHITWOETH  STANDARD  THREADS  43

Exercises.   Whit  worth  Threads

1.  Find  the  depth  of  a  Whitworth  thread  of  ^-inch  pitch.
2.  Find  the  double  depth  of  a  Whitworth  thread  with
7  threads  to  the  inch.
Find  the  radius  for  the  point  of  the  tool  for  cutting  a  Whit-
worth thread  of  which  the  pitch  in  each  case  is  as  follows :

3.  0.4".        4.    i".        5.    i".        6.    i".        7.  -s\"'        8.  &"•

9.  Find  the  tap-drill  size  for  a  Whitworth  thread  of  which
the  outside  diameter  is  4".
