This section is from the book "Turning And Mechanical Manipulation", by Charles Holtzapffel. Also available from Amazon: Turning and Mechanical Manipulation.

Number | Diameter of Bore in Hundredths. | Weight of Leadenbullet in Grains. |

5 | •98 | 1400 |

6 | •93 - | 1666 2/3 |

7 | •89 | 1000 |

8 | •85 - | 875 |

9 | •81 - | 777 7/9 |

10 | •79 | 700 |

M 11 P | •77 - | 636 4/11 |

12 | •75 x | 583 1/3 |

13 | .74 - | 538 6/13 |

M l4 S | •72 - | 500 |

Number. | Diameter of Bore in Hundredths. | Weight of Leadenbullet in Grains. |

15 | •70 x | 466 2/3 |

16 | •69 - | 437 1/2 |

C 17 P | •67 x | 411 13/17 |

18 | •66 | 388 5/9 |

19 | •65 x | 368 5/19 |

20 | •63 x | 355 |

21 | •63 | 333 1/3 |

22 | •62 x | 318 2/11 |

23 | •61 x | 304 8/23 |

24 | •61 | 291 2/3 |

Number. | Diameter of Bore in Hundredths. | Weight of Leadenbullet in Grains. |

25 | •60 x | 280 |

26 | •59 x | 269 3/13 |

27 | •59 | 269 7/27 |

28 | •58 x | 250 |

29 | •58 - | 241 11/29 |

30 | •57 | 233 1/3 |

31 | •56 x | 225 25/31 |

32 | •56 - | 218 3/4 |

From the perusal of the foregoing particulars of numerous gages, employed in different branches of mechanical art, it will have been seen that little analogy, on the one hand, but great confusion on the other, exist in such of the gages as have been referred to; and the author will now briefly state the remedy he would suggest to obviate the difficulty in the most simple and inexpensive manner.

The remedy proposed to rem ore the arbitrary incongruous system of gages now used, is simply and in every one of the cases above referred to, and also in all others requiring minute measures, to employ the decimal divisions of the inch, and those under their true appellations.

Thus for most purposes the division of the inch into one hundred parte would be sufficiently minute, and the measures 1. 2. 5.10. 15 or 100 hundredths, would be also sufficiently impressive to the mind; their quantities might be written down as 1. 2.

5.10. 15 or 100 hundredths, as the decimal mode of expression might if preferred be safely abandoned, and the method would be abundantly distinct for common use if the word "Hundredths" were stamped upon the gage, to show that its numerals denoted hundredths of the inch, quantities which could be easily verified by all.

It does not follow that the entire hundred notches should be at all times used, as in many cases it might suffice that below 20 hundredths, every size should be employed; - from 20 to 50 hundredths, every alternate size, - from 50 to 100 hundredths every fifth size. As at present also, the upper or lower part of the series of terms might be omitted to any desired extent, in those cases where they were beyond the particular wants of the artizan or the particular branch of trade, in order to lessen the bulk and expense of the gage.

It may be objected to this scheme, that for the more valuable metals, and the more minute purposes, the quantity of the one hundredth of an inch is too coarse a difference. Two facile modes of remedy may be here applied. The first to make half sizes: thus 8 1/2 or 8.5 would of course denote the medial interval between 8 and 9 hundredths. Or secondly, and preferably, below one tenth of an inch, a finer scale might be substituted for the more minute and delicate purposes, namely a gage based in precisely the same manner, on the thousandth of the inch as the unit, which would give a much finer degree of subdivision than is afforded by any of the arbitrary gages in general use; in this case the intervals being derived from the thousandth of an inch, the word "Thousandths" should be stamped on every such gage.

In practice no difficulty could be seriously felt even without this precaution of marking the gages respectively with the word Hundredth or Thousandths; as we should not more readily mistake 5 thousandths for 5 hundredths, than we should, 5 tenths or half an inch, for 5 whole inches, or 5 entire inches for as many feet

Neither is it to be admitted that no such gages are attainable as may be read off in hundredths or thousandths. The demand would immediately create the supply, and there could be no more difficulty in constructing the gages of the customary forms, with notches made to systematic and defined measures, that may be easily arrived at or tested, than with their present unsystematical and arbitrary measures, which do not admit of verification.

Besides, for those who desire to possess them, several very correct decimal gagc3 already exist, amongst which may be cited the decimal sector gages long since recommended, and published by the Society of Arts, Edinburgh, and various sliding gages with verniers some to read off in hundreds, and finer ones in thousandths, of the inch, all of which have been long and constantly used in the author's manufactory.

To these may be added - La Riviere's gage, modified and enlarged from that used for the balance springs of watches amongst the Geneva watchmakers. - Chater and Hayward's gage for sheet metals and glass. - Walker's gage for sheet iron. - Whitworth's micrometer gage and others - which may be severally read off to the thousandth of the inch, and even more minute quantities, and amongst which kinds sufficient choice exists for almost every purpose.

The advantages offered by this proposed application of decimal measures, appear to be numerous and considerable, the more especially in those cases of small measures, where the ordinary wire gages on the one hand, and the coarse division of ordinary foot rules on the other, are obviously insufficient for accurate purposes. Amongst these advantages may be enumerated the following:

The proposed decimal scheme would introduce one universality of system, intelligible alike to all, instead of the numerous and irregular measures now used, which are but partially and indifferently known and lead to frequent mistakes.

It would giro a superior idea of particular magnitude, and enable the theoretical and practical man to proofed with so much more decision in their respective communications.

In conveying verbal or written instructions, the system would be in every way superior to the usual methods, as being almost free from the chance of misunder standing, more especially as some of the decimal sliding gages are so small as hardly to take-up more room in the pocket than an ordinary penknife, and might be therefore continually within reach for reference.

When certain objects are required to be so proportioned as to constitute a series, the intervals between the decimal measures would be far more easily arranged and appreciated, than those of vulgar fractions; and if calculation were referred to, the decimal figures, especially when divested of the decimal point, and the zeros to the right of the same, would be immediately intelligible to the least informed, from being then no more in fact than simple numerals.

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