| No. of Gauge. | Diameter of Bore. | No. of Gauge. | Diameter of Bore. | ||||||
| 4 | varies from | 1.052 | to | 1.000 | 14 | varies from | .693 | to | .680 |
| 6 | „ | .919 | „ | .900 | 16 | „ | .662 | „ | .650 |
| 8 | „ | .835 | „ | .820 | 20 | „ | .615 | „ | .610 |
| 10 | „ | .775 | „ | .760 | 24 | „ | .579 | „ | .577 |
| 12 | „ | .729 | „ | .750 | 28 | „ | .550 | „ | .548 |
The following table gives the result of some recent experiments made by Mr. David Kirkaldy, of London, to ascertain the tensile strength and resistance to torsion of wire made of various materials:
| Kind of wire tested. | Pulling stress per sq. in. | ||
| Unannealed. | Annealed. | ||
| Pounds. | Pounds. | ||
| Copper | 63,122 | 37,002 | |
| Brass | 81,156 | 51,550 | |
| Charcoal iron | 65,834 | 46,160 | |
| Coke iron | 64,321 | 61,294 | |
| Steel | 120,976 | 74,637 | |
| Phosphor bronze, | No. 1 | 159,515 | 58,853 |
| „ | No. 2 | 151,119 | 64,569 |
| „ | No. 3 | 139,141 | 54,111 |
| „ | No. 4 | 120,900 | 53,381 |
| Kind of wire tested. | Ultimate extension in per cent. Annealed. | No. of twists in 5 inches. | ||||
| Unannealed. | Annealed. | |||||
| Copper | 34 | .1 | 86 | .8 | 96 | |
| Brass | 36 | .5 | 14 | .7 | 57 | |
| Charcoal iron | 28 | 48 | 87 | |||
| Coke iron | 17 | 26 | 44 | |||
| Steel | 10 | .9 | [28] | 79 | ||
| Phosphor bronze, | No. 1 | 46 | .6 | 13 | .3 | 66 |
| „ | No. 2 | 42 | .8 | 15 | .8 | 60 |
| „ | No. 3 | 44 | .9 | 17 | .3 | 53 |
| „ | No. 4 | 42 | .4 | 13 | 124 | |
[28] Of the eight pieces of steel tested, three stood from forty to forty-five twists, and five stood one and a half to four twists.
The following, on some experiments upon the elasticity of wires, is from the report of a committee read before the British Association at Sheffield, England.
“The most important of these experiments form a series that have been made on the elastic properties of very soft iron wire. The wire used was drawn for the purpose, and is extremely soft and very uniform. It is about No. 20 B.W.G., and its breaking weight, tested in the ordinary way, is about 45 lbs. This wire has been hung up in lengths of about 20 ft., and broken by weights applied, the breaking being performed more or less slowly.
“In the first place some experiments have been tried as to the smallest weight which, applied very cautiously and with precautions against letting the weight run down with sensible velocity, will break the wire. These experiments have not yet been very satisfactorily carried out, but it is intended to complete them.
“The other experiments have been carried out in the following way: It was found that a weight of 28 lbs. does not give permanent elongation to the wire taken as it was supplied by the wire drawer. Each length of the wire, therefore, as soon as it was hung up for experiment, was weighted with 28 lbs., and this weight was left hanging on the wire for 24 hours. Weights were then added till the wire broke, measurements as to elongation being taken at the same time. A large number of wires were broken with equal additions of weight, a pound at a time, at intervals of from three to five minutes—care being taken in all cases, however, not to add fresh weight if the wire could be seen to be running down under the effect of the weight last added. Some were broken with weights added at the rate of 1 lb. per day, some with 3⁄4 lb. per day, and some with 1⁄2 lb. per day. One experiment was commenced in which it was intended to break the wire at a very much slower rate than any of these. It was carried on for some months, but the wire unfortunately rusted, and broke at a place which was seen to be very much eaten away by rust, and with a very low breaking weight. A fresh wire has been suspended, and is now being tested. It has been painted with oil, and has now been under experiment for several months.
“The following tables will show the general results of these experiments. It will be seen, in the first place, that the prolonged application of stress has a very remarkable effect in increasing the strength of soft iron wire. Comparing the breaking weights for the wire quickly broken with those for the same wire slowly broken, it will be seen that in the latter case the strength of the wire is from two to ten per cent. higher than in the former, and is on the average about five or six per cent. higher. The result as to elongation is even more remarkable, and was certainly more unexpected. It will be seen from the tables that, in the case of the wire quickly drawn out, the elongation is on the average more than three times as great as in the case of the wire drawn out slowly. There are two wires for which the breaking weights and elongations are given in the tables, both of them ‘bright’ wires, which showed this difference very remarkably. They broke without showing any special peculiarity as to breaking weight, and without known difference as to treatment, except in the time during which the application of the breaking weight was made. One of them broke with 441⁄4 lbs., the experiment lasting one hour and a half; the other with 47 lbs., the time occupied in applying the weight being 39 days. The former was drawn out by 28.5 per cent. on its original length, the latter by only 4.79 per cent.