Table 7. Numbers Of Steps In Bolts' And Taps' Screws Having Short Steps

Extreme diameters of taps or rods.

Numbers of steps per inch of length.

Inches.

1/4

20

5/16

18

3/8

16

7/16

14

1/2

12

9/16

12

5/8

11

11/16

11

3/4

10

13/6

10

7/8

10

1 5/1 6

10

1

9

1 1/16

9

1 1/8

9

1 3/16

9

1 1/4

8

1 5/16

8

Extreme diameters of taps or rods.

Numbers of steps per inch of length.

Inches.

1 3/8

8

1 7/16

8

1 1/2

7

1 9/16

7

1 5/8

7

1 11/16

7

1 3/4

6 1/2

1 13/16

6 1/2

1 7/8

6 1/2

1 15/16

6 1/2

2

6

2 1/16

6

2 1/8

6

2 3/16

6

2 1/4

5 1/2

2 5/16

5 1/2

2 3/8

5 1/2

2 7/16

5 1/2

Extreme diameters of taps or rods.

Numbers of steps per inch of length.

Inches.

2 1/2

5

2 9/16

5

2 5/8

5

2 11/16

5

2 3/4

4 3/4

2 13/16

4 3/4

2 7/8

4 3/4

2 15/16

4 3/4

3

4 1/2

3 1/4

4 1/2

3 1/2

4 1/2

3 3/4

4 1/2

4

4 1/4

4 1/4

4 1/4

4 1/2

4 1/4

4 3/4

4 1/4

5

4

5 1/4

4

Extreme diameters of taps or rods.

Numbers of steps per inch of length.

Inches.

5 /12

4

5 3/4

4

6

3 3/4

6 1/4

3 3/4

6 1/2

3 3/4

6 3/4

3 3/4

7

3 1/2

7 1/4

3 1/2

7 1/2

3 1/2

7 3/4

3 1/4

8

3 1/4

8 1/2

3 1/4

9

3 1/4

9 1/2

3 1/4

10

3

10 1/2

3

11

3

11 1/2

3

12

3

In order to screw taps or rods with thin threads, the teeth of the screw-tools employed are shaped with the same hobs as those for thick threads, except those having 4 3/4 steps, 61/2 steps, or other similar fractional quantity per inch; tools for such threads are shaped with special hobs. The objection to a fraction on paper amounts to nothing in practice, because the same lathes, wheels, and tables of wheels, are used to produce threads of all classes, and are employed with equal facility for either sort of work. Taps having short steps have comparatively short screw-portions, the lengths and diameters of their stems being about the same as those of taps having longer steps. In Table 8 the length of each screw-part is shown opposite the tap's extreme diameter or thickness.

Table 8. Screw-Portions Of Long Taper Taps Having Short-Step Screws

Extreme diameters.

Lengths of screw-portions.

Inches.

Inches.

3/4

5 1/6

13/16

5 1/2

7/8

5 3/4

15/16

6

1

6 1/4

l 1/16

6 3/5

1 1/5

6 1/2

1 3/16

6 5/8

1 1/4

7

1 5/16

7 1/8

1 5/6

7 1/4

1 7/16

7 3/8

Extreme diameters.

lengths of screw-portions.

Inches.

Inches.

1 1/2

7 1/2

1 9/16

7 3/4

15/8

8 1/8

1 11/6

8 1/4

1 3/4

8 3/4

1 13/16

9 1/8

1 7/8

9 3/8

1 15/16

9 5/8

2

10

2 1/16

10 1/4

2 1/5

10 3/8

2 /16

10 5/8

Extreme diameters.

Lengths of screw-portions.

Inches.

Inches.

2 1/4

11

2 5/18

11 1/4

2 3/8

113/8

2 7/16

11 5/8

2 1/2

12

2 9/16

12 1/4

2 5/8

12 3/8

2 11/16

12 3/4

2 3/4

13 1/4

2 13/16

13 1/2

2 7/8

13 3/4

2 15/16

14

3

14 1/4