22.2 : 22.2 :: 508 : 508.

In forging a ring Ave do not require to measure the two-tenths of a millimetre, and the result would meet the requirement if 22 were stated instead of 22.2. But in the case of bar an inch thick being used it would be necessary to state 25.4 instead of 25 ; twenty-five millimetres being about half a millimetre less than one inch. In millimetres, the proposition relating to bar one inch thick is thus written :

25.4 : 22.2 :: 508 : 444.

To ascertain the number of millimetres contained in any mentioned number of inches or parts of inches, it is only necessary to divide the mentioned number by •03937, always indicating the fractions by decimal symbols; and the quotient or result will indicate the number of millimetres and parts.

And to ascertain the number of inches and parts of inches contained in any mentioned number of millimetres, it is only necessary to multiply the mentioned number by '03937, and the product or result will indicate the number required. For example, 500 millimetres equal half a metre; and 500 x .03937 of an inch = 19.685 inches. And twice this amount of inches is a complete metre of 39.37 inches. A nearer approach to precision is attained by using the fraction indicated by .0393708, instead of .03937.

A few dimensions of rings are indicated by the Tables, as examples of lengths of iron required for the different diameters.

Table 1 contains only the diameters and circumferences of the mean or middle circles of the face-sides, the lengths of bar required being the same as the lengths of the circumferences. These dimensions are only available when the thickness of the bar is the same as that of the ring when forged, whatever the required thickness may be. If a ring is to be 11.5 centimetres in diameter at the mean or mid-circle of the face, the necessary length of bar is 36.12 centimetres, which is pointed to in the Table at line 14. The thickness of the bar may be 1, 2, or 3 centimetres, being the same as that of the ring itself.

But if it is necessary to use remnants of bar which are thicker than the rings intended, the necessary length of bar for making a ring of the mentioned diameter may be seen in Table 2 ; if not in this Table, the length may at any time be ascertained by applying the rule just given.

By reference to line 109 of Table 2 it will be perceived that 91/2 inches of bar 7/8 thick is sufficient for a ring whose mid-circle diameter is to be 41/4 inches, and forged thickness to be 5/8. And if remnants of 7/8 bar are to be used, it may be known what lengths of remnants are required for drawing down to 5/8 thick. Also by referring to line 135 in the same Table, it will be perceived that 49 1/2 inches of bar one inch thick may be drawn down or reduced in order to make a ring which is required to be 3/4 thick, and whose mid-circle diameter is to be 21 inches.

When cutting the lengths of bar, it is not necessary to add any for scarfing, because whatever amount of iron may be upset will be afterwards drawn down in welding; but if the iron is to be heated a number of times, an eighth of an inch should be added for that which may be burnt or taken from the iron by the fire.

The width of a ring is sometimes named its height. No mention is here made of the widths or heights of rings, because their widths are the same as the widths of the bars of which the rings are made; consequently, the widths of rings are independent of the dimensions here given and referred to.

Table 1

Line.

Diameters of mean-circles of face-sides of rings, in centimetres.

Lengths of circumferences of mean-circles of face-sides of rings, in centimetres.

1 . . .

5

15.7

2 . .

5.5

17.27

3 . .

6

1884

4 . .

6.5

20..42

5 . .

7

21.99

6 . .

7.5

23.56

7 . .

8

2513

8 . .

8.5

26.7

9 . .

9

28.27

10 . .

9.5

29.84

11 . .

10

31.41

12 . .

10.5

32.98

13 . .

11

34.55

14 . .

11.5

3612

15 . .

12

37.69

16 . .

12.5

3927

17 . .

13

40..84

18 . .

13.5

42.41

19 . .

14

43.98

20 . .

14.5

45.55

Line.

Diameters of mean-circles of face-sides of rings, in centimetres.

Lengths of circumferences of mean-circles of face-sides of ring», in centimetres.

21. . .

15

47.12

22. . .

15.5

48.69

23. . .

16

50.26

24. . .

16.5

51.83

25. . .

17

53.4

26. . .

175

54.97

27. . .

18

56.54

28. . .

18.5

5811

29. . .

19

59.69

30. . .

19.5

61.26

81.,...

20

62.83

32. . .

20.5

64.4

33. . .

21

65.97

34. . .

21.5

67.54

35. . .

22

6911

36. . .

22.5

70.68

37. . .

23

7225

38. . .

23.5

73.82

39. . .

24

75.39

40. . .

24.5

76.96

Line.

Diameters of mean-circles of face-sides of rings, in centimetres.

Lengths of circumferences of mean-circles of face-sides of rings, in centimetres.

41 . . .

25

78.54

42. . .

25.5

801

43. . .

26

81.68

44. . .

26.5

83.25

45. . .

27

84.82

46. . .

27.5

86.39

47. . .

28

87.96

48. . .

28.5

89.53

49. . .

29

911

50. . .

29.5

92.67

51. . .

30

94.24

52. . .

30.5

95.81

53. . .

31

97.38

54. . .

31.5

98.96

55. . .

32

100.53

5G. . .

325

102.1

57. . .

33

103.67

58. . .

33.5

105.24

Table 2

Required forged thickness of rings' face-sides ; or distances from the inner circumferences to the outer.

Diameters of mean-circles of rings' face-sides.

Lengths of circumferences of the mean-circles of rings' face-sides.

Lengths of bar required.

Thickness of bar from which the rings are made

Line.

Inches.

Inches.

Inches.

1 . . .

l/4

1

3 1/8

3 1/8

1/4

2 . . .

1/4

1 1/8

3 1/2

3 1/2

1/4

3 . . .

1/4

1 1/4

3 15/16

3 15/16

1/4

4 . . .

1/4

1 3/8

4 5/16

4 5/16

1/4

5 . . .

1/4

1 1/2

4 11/16

4 11/16

1/4

6 . . .

1/4

1 5/8

5 1/8

5 1/8

1/4

7 . . .

1/4

1 3/4

5 1/2

5 1/2

1/4

8 . . .

1/4

17/8

5 7/8

5 7/8

1/4

9 . . .

1/4

2

6 5/16

6 5/16

1/4

10 . . .

1/4

2 1/8

6 11/16

6 11/16

1/4

11 . . .

1/4

2 1/4

7

7

1/4

12 . . .

1/4

23/8

7 7/16

7 7/16

1/4

13 . . .

1/4

2 1/2

7 7/8

7 7/8

1/4

14 . . .

1/4

2 5/8

8 1/4

8 1/4

1/4

15 . . .

1/4

2 3/4

8 5/8

8 5/8

1/4

16 . . .

1/4

2 7/8

9

9

1/4

17 . . .

1/4

3

9 7/16

9 7/16

1/4

18 . . .

1/4

3 1/8

9 13/16

9 13/16

1/4

19 . . .

1/4

3 1/4

10 1/4

10 1/4

1/4

20 . . .

3/8

3

9 7/16

9 7/16

3/8

21 . . .

3/8

3 1/8

9 13//16

9 13/16

3/8

22 . . .

3/8

3 1/4

10 1/4

10 1/4

3/8

Required forged thickness of rings' face-sides; or distances from the inner circumferences to the outer.

Diameters of mean-circles of rings' face-sides.

Lengths of circumferences of the mean-circles of rings' face-sides.

Lengths of bar required.

Thickness of bar from which the rings are made.

Line.

Inches.

Inches.

Inches.

Inches.

23 . . .

3/8

3 3/8

10 9/16

10 9/16

3/8

24 . . .

3/8

3 1/2

11

11

25 . . .

3/8

3 5/8

11 3/8

11 3/8

3/8

26 . . .

3/8

3 3/4

11 3/4

11 3/4

3/8

27 . . .

3/8

3 7/8

12 3/16

12 3/16

3/8

28 . . .

3/8

4

12 9/16

129/16

3/8

29 . . .

3/8

4 1/8

12 5/16

12 15/16

3/8

30 . . .

3/8

4 1/4

13 3/8

13 3/8

3/8

31 . . .

3/8

4 3/8

13 3/4

13 3/4

3/8

32 . . .

3/8

4 1/2

14 1/8

14 1/8

3/8

33 . . .

3/8

4 5/8

14 1/2

14 1/2

3/8

34 . . .

3/8

4 3/4

14 15/16

14 15/16

3/8

35 . . .

3/8

4 7/8

15 5/16

15 5/16

3/8

36 . . .

3/8

5

15 11/16

15 11/16

3/8

37 . . .

3/8

5 1/8

16 1/16

16 1/16

3/8

38 . . .

3/8

5 1/4

16 1/2

16 1/2

3/8

39 . . .

3/8

5 3/8

16 7/8

16 7/8

3/8

40 . . .

3/8

5 1/2

17 1/4

17 1/4

3/8

41 . . .

3/8

5 5/8

17 11/16

17 11/16

3/8

42 . . .

3/8

5 3/4

18

18

3/8

43 . . .

3/8

5 7/8

18 1/2

18 1/2

3/8

44 . . .

3/8

6

18 13/16

18 13/16

3/8

Table 2 - Continued

Required forged thickness of rings' face-sides; or distances from the inner circumferences to the outer.

Diameters of mean-circles of rings' face-sides.

Lengths of circumferences of the mean-circles of rings' face-sides.

Lengths of bar required.

Thickness of bar from which the rings are made.

Line.

Inches.

Inches.

Inches.

Inches.

Inches,

45 . . .

3/8

6 1/8

19 1/4

19 1/4

3/8

46 . . .

3/8

6 1/4

19 5/8

19 5/8

3/8

47 . . .

3/8

6 3/8

20

20

3/8

48 . . .

1/2

3

9 7/16

9 7/16

1/2

49 . . .

1/2

3 1/8

9 13/16

9 13/16

1/2

50 . . .

1/2

3 1/4

10 1/4

10 1/4

1/2

51 . . .

1/2

3 3/8

10 9/16

10 9/16

1/2

52 . . .

1/2

3 1/2

11

11

1/2

53 . . .

1/2

3 5/8

11 3/8

11 3/8

1/2

54 . . .

1/2

3 3/4

11 3/4

11 3/4

1/2

55 . . .

1/2

3 7/8

12 3/16

12 3/16

1/2

56 . . .

1/2

4

12 9/6

12 9/1 6

1/2

57 . . .

1/2

4 1/8

12 15/16

12 15/16

1/2

58 . . .

1/2

4 1/4

13 3/8

13 3/8

1/2

59 . . .

1/2

4 3/8

13 3/4

13 3/4

1/2

60 . . .

1/2

4 1/2

14 1/8

14 1/8

1/2

61 . . .

1/2

4 5/8

14 1/2

14 1/2

1/2

62 . . .

1/2

4 3/4

14 15/16

14 15/16

1/2

63 . . .

1/2

4 7/8

15 5/16

15 5/16

1/2

64 . . .

1/2

5

15 11/16

15 11/16

1/2

65 . . .

1/2

5 1/8

l6 1/16

16 1/1

1/2

66 . . .

1/2

5 1/4

16 1/2

16 1/2

1/2

67 . . .

1/2

5 3/8

16 7/8

l6 7/8

1/2

68 . . .

1/2

5 1/2

17 1/4

17 1/4

1/2

69 . . .

1/2

5 5/8

17 11/16

17 11/16

1/2

70 . . .

1/2

5 3/4

18

18

1/2

71 . . .

1/2

5 7/8

18 1/2

18 1/2

1/2

72 . . .

1/2

6

18 13/16

18 13/16

1/2

73 . . .

1/2

6 1/8

19 1/4

19 1/4

1/2

74 . . .

1/2

6 1/4

19 5/8

19 5/6

1/2

75 . . .

1/2

6 3/8

20

20

1/2

76 . . .

1/2

6 1/2

20 7/16

20 7/16

1/2

77 . . .

1/2

6 5/8

20 13/16

20 13/16

1/2

78 . . .

1/2

6 3/4

21 3/16

21 3/16

1/2

79 . . .

1/2

6 7/8

21 9/16

219/16

1/2

80 . . .

1/2

7

22

22

1/2

81 . . .

1/2

7 1/8

22 3/8

22 3/8

1/2

82 . . .

1/2

7 1/4

22 3/4

22 3/4

1/2

83 . . .

1/2

7 3/8

23 3/16

23 3/16

1/2

84 . . .

1/2.

7 1/2

23 9/16

23 9/16

1/2

85 . . .

1/2

7 5/8

23 15/16

23 15/16

1/2

86 . . .

1/2

7 3/4

24 3/8

24 3/8

1/2

87 . . .

1/2

7 7/8

243/4

24 3/4

1/2

88 . . .

1/2

8

25 1/8

25 1/8

1/2

89 . . .

1/2

8 1/8

25 1/2

25 1/2

1/2

90 . . .

1/2

8 1/4

25 15/16

25 15/16

1/2

91 . . .

1/2

8 3/8

26 5/16

26 5/16

1/2

92 . . .

1/2

8 1/2

26 11/16

26 11/16

1/2

93 . . .

1/2

8 5/8

27

27

1/2

94 . . .

1/2

8 3/4

27 1/2

27 1/2

1/2

95 . . .

1/2

8 7/8

27 7/8

27 7/8

1/2

96 . . .

1/2

9

28 1/4

28 1/4

1/2

Required forged thickness of rings' face-sides ; or distances from the inner circumferences to the outer.

Diameters of mean-circles of rings' face-sides.

Lengths of circumferences of the mean-circles of rings' face-sides.

Lengths of bar required.

Thickness of bar from which the rings are made.

Line.

Inches.

Inches.

Inches.

Inches.

Inches.

97 . .

5/8

3 1/2

11

11

5/8

98 . .

5/8

3 3/4

11 3/4

11 3/4

5/8

99 . .

5/8

4

12 9/16

12 9/16

5/8

100 . .

5/8

4 1/4

18 3/8

13 3/8

5/8

101 . .

5/8

4 1/2

141/8

14 1/8

5/8

102 . .

5/8

4 3/4

l4 15/16

14 15/16

5/8

103 . .

5/8

5

15 11/16

15 11/16

5/8

104 . .

5/8

5 1/4

16 1/2

16 1/2

5/8

105 . .

5/8

5 1/2

17 1/4

17 1/4

5/8

106 . .

5/8

5 3/4

18

18

5/8

107 . .

5/8

6

18 13/16

18 13/16

5/8

108 . .

5/8

4

12 9/16

8 15/16

7/8

109 . .

5/8

4 1/4

13 3/8

9 1/2

7/8

110 . .

5/8

4 1/2

14 1/8

10 1/16

7/8

1ll . .

5/8

4 3/4

l4 13/16

109/16

7/8

112 . .

5/8

6 1/4

19 5/8

19 5/8

5/8

113 . .

5/8

6 1/2

20 7/16

20 7/16

5/8

114 . .

5/8

6 3/4

21 3/16

21 3/16

5/8

115 . .

5/8

7

22

22

5/8

116 . .

5/8

8

25 1/8

25 1/8

5/8

117 . .

5/8

9

28 1/4

28 1/4

5/8

118 . .

5/8

10

31 7/16

31 7/16

5/8

119 . .

5/8

11

34 9/16

34 9/16

5/8

120 . .

5/8

12

37 11/16

37 11/16

5/8

121 . .

3/4

7 1/2

23 9/16

23 9/16

3/4

122 . .

3/4

8 1/2

26 11/16

26 11/16

3/4

123 . .

3/4

9 1/2

29 7/8

29 7/8

3/4

124 . .

3/4

10 1/2

33

33

3/4

125 . .

3/4

11 1/2

36 1/8

36 1/8

3/4

126 . .

3/4

12 1/2

39 1/4

39 1/4

3/4

127 . .

3/4

13 1/2

42 7/16

42 7/16

3/4

128 . .

3/4

14 1/2

45 9/16

45 9/16

3/4

129 . .

3/4

15 1/2

48 11/16

48 11/16

3/4

130 . .

3/4

16 1/2

51 16/16

51 13/16

3/4

131 . .

3/4

17 1/2

55

55

3/4

132 . .

3/4

18 1/2

58 1/8

58 1/8

3/4

133 . .

3/4

19 1/2

61 1/4

61 1/4

3/4

134 . .

3/4

20

62 13/16

47 1/8

10

135 . .

3/4

21

66

49 1/2

10

136 . .

3/4

22

69 1/8

51 13/16

1.0

137 . .

3/4

23

72 1/4

54 3/16

10

138 . .

3/4

24

75 3/8

56 9/16

1.0

139 . .

3/4

25

78 9/16

78 9/16

3/4

140 . .

3/4

26

81 11/16

81 11/16

3/4

141 . .

3/4

27

84 13/16

84 13/16

3/4

142 . .

3/4

28

87 15/16

87 15/16

3/4

143 . .

3/4

29

91 1/16

91 1/16

3/4

144 . .

7/8

30

94 1/4

94 1/4

7/8

145 . .

7/8

31

97 3/8

97 3/8

7/8

146 . .

7/8

32

100 1/2

100 1/2

7/8

147 . .

7/8

33

103 11/16

103 11/16

7/8

148 . .

7/8

34

106 13/16

106 13/16

7/8

To prevent burning of the rings, and to promote an easy welding, sand, loam, or powdered glass is applied to the iron at the time it commences to melt. The sand is placed upon the iron, while it is in the fire, by means of a ladle or spoon having a long handle; the blast being gently administered at the moment. Large rings require a fire which is open in front, but closely built on the opposite side, and having a strong, thick arch, to cause the flame to whirl around the joint instead of being blown upon one side only. While the rings are being curved upon the beak of the anvil, or while being welded, stretched, flattened, or smoothed, a tongs, represented by Fig. 98, is required, by which to grip the rings in a convenient and safe manner.

When it is necessary to weld together the two scarfs of a ring so that the joint may be almost as solid and strong as any other part of the ring, great care must be exercised in selecting a tough, fibrous iron, and in having a weld free from burnt iron, slag, or other foreign matter. To prevent the slag adhering to the joint, a large supply of sand is given, and, by the sand becoming liquid while upon the surface of the iron, whatever slag may be formed upon the joint is washed off. This slag is produced by the fusion of the impurities in the coal or iron, and constitutes part of the clinker which accumulates at the bottom of the fire.