Elric
Well-Known Member
How Gun Barrels Are Straightened
Amateur Mechanics, September 1883, pages 271-272
https://books.google.com/books?id=W...nepage&q=Gun-Barrels Are Straightened&f=false
THE straightening of a gun barrel is a very delicate and difficult mechanical operation, in which no machinery has as yet successfully competed with the human hand and eye. In addition to long experience, a natural adaptation to the work is necessary in order to attain any considerable degree of proficiency. The business is understood by comparatively few; indeed, many who attempt to learn it can make no progress whatever.
A plate of ground glass, size about 12 x 15 inches, and set in a dark frame, hangs against a window, some twenty feet from the workman. Horizontally across this glass is a bar of dark coloured wood, three-eighths of an inch in width. Upon a convenient rest the operator lays a gun barrel, looking through it at the bar, which casts two fine lines or "shades" in the barrel. These join at the farther end, and gradually diverge, a break occurring in them wherever there is a "crook" in the barrel ; the workman thus being enabled to detect the slightest deviation. In order to straighten the barrel it is put on a straightening block, and the mechanic strikes it a blow with a steel hammer (these hammers vary in weight from three and a half to four pounds), the force of which is graduated according to kind of crook, size of barrel, and quality of steel. This alternate sighting and hammering is many times repeated, the barrel being turned slowly around while sighting, in order to locate any inequality which may exist at any point. An inexperienced man may soon learn to tell if the barrel is straight, but it requires much practice to strike in exactly the right spot and with the proper force. The blow must be made in the exact place where the crook occurs, and if too hard, is worse than no blow at all. The barrel is thus treated six or seven times; and is re- bored after each successive straightening.
Towards the last finer crooks, known as "kinks," appear. These are shown by waves, instead of breaks, in the lines, and require light taps rather than blows. The nearer the barrel approaches perfection the more skill is required to manipulate these kinks into unbroken lines. This is but one of many interesting operations through which a gun passes during the process of manufacture, in any of which its shooting qualities may be seriously impaired. A blow too light, or too heavy, too many, or too few; a discrepancy of one-thousandth of an inch in the boring or rifling may transpose into a very poor gun one that would otherwise have been beyond criticism.
Formerly the process of straightening was effected in a very different manner, which, compared with the present mode, is both crude and unsatisfactory. One end of a silk or seaweed thread was attached to a bow a few inches longer than the barrel to be operated upon, the other end to a small lead weight known as a " sinker." This being dropped through the barrel, the bow was sprung, the thread drawn taut, and fastened thereon. The workman then looked through the barrel, observing where the light shone under the thread, thus detecting any imperfections. A barrel straightened in this manner, however, shows numerous defects when subjected to the modern method. In the old way the workman, standing near a window, examines and straightens the half nearest him; in the new he is away from the light, and operates upon the other half, looking through cither end as occasion requires.
The process described never fails to attract the attention of visitors at an armoury, and is always looked upon as an interesting novelty. In view of the fact that the accuracy of a bullet's flight is dependent upon the perfection of less than one yard of barrel, it is wonderful that such good shooting can be done at more than one thousand times that distance.
Amateur Mechanics, September 1883, pages 271-272
https://books.google.com/books?id=W...nepage&q=Gun-Barrels Are Straightened&f=false
THE straightening of a gun barrel is a very delicate and difficult mechanical operation, in which no machinery has as yet successfully competed with the human hand and eye. In addition to long experience, a natural adaptation to the work is necessary in order to attain any considerable degree of proficiency. The business is understood by comparatively few; indeed, many who attempt to learn it can make no progress whatever.
A plate of ground glass, size about 12 x 15 inches, and set in a dark frame, hangs against a window, some twenty feet from the workman. Horizontally across this glass is a bar of dark coloured wood, three-eighths of an inch in width. Upon a convenient rest the operator lays a gun barrel, looking through it at the bar, which casts two fine lines or "shades" in the barrel. These join at the farther end, and gradually diverge, a break occurring in them wherever there is a "crook" in the barrel ; the workman thus being enabled to detect the slightest deviation. In order to straighten the barrel it is put on a straightening block, and the mechanic strikes it a blow with a steel hammer (these hammers vary in weight from three and a half to four pounds), the force of which is graduated according to kind of crook, size of barrel, and quality of steel. This alternate sighting and hammering is many times repeated, the barrel being turned slowly around while sighting, in order to locate any inequality which may exist at any point. An inexperienced man may soon learn to tell if the barrel is straight, but it requires much practice to strike in exactly the right spot and with the proper force. The blow must be made in the exact place where the crook occurs, and if too hard, is worse than no blow at all. The barrel is thus treated six or seven times; and is re- bored after each successive straightening.
Towards the last finer crooks, known as "kinks," appear. These are shown by waves, instead of breaks, in the lines, and require light taps rather than blows. The nearer the barrel approaches perfection the more skill is required to manipulate these kinks into unbroken lines. This is but one of many interesting operations through which a gun passes during the process of manufacture, in any of which its shooting qualities may be seriously impaired. A blow too light, or too heavy, too many, or too few; a discrepancy of one-thousandth of an inch in the boring or rifling may transpose into a very poor gun one that would otherwise have been beyond criticism.
Formerly the process of straightening was effected in a very different manner, which, compared with the present mode, is both crude and unsatisfactory. One end of a silk or seaweed thread was attached to a bow a few inches longer than the barrel to be operated upon, the other end to a small lead weight known as a " sinker." This being dropped through the barrel, the bow was sprung, the thread drawn taut, and fastened thereon. The workman then looked through the barrel, observing where the light shone under the thread, thus detecting any imperfections. A barrel straightened in this manner, however, shows numerous defects when subjected to the modern method. In the old way the workman, standing near a window, examines and straightens the half nearest him; in the new he is away from the light, and operates upon the other half, looking through cither end as occasion requires.
The process described never fails to attract the attention of visitors at an armoury, and is always looked upon as an interesting novelty. In view of the fact that the accuracy of a bullet's flight is dependent upon the perfection of less than one yard of barrel, it is wonderful that such good shooting can be done at more than one thousand times that distance.