The superior quality of the work done by the machine would alone make its use advantageous; but to this is added greatly increased amount of work done.
The difference in favor of the riveting machine over hand riveting is at least ten to one.
In a large establishment a record of the number of rivets driven by the hand-driving gang, also by the gang at the steam-riveting machine for a long period of time, in both cases making no allowances of any kind of delays, the rivets driven per month by each was—for the hand driven rivets at the rate of twelve rivets per hour, and for the machine driven rivets, 120 per hour. In the case of the hand driven rivets the boiler remains stationary and the men move about it, while the machine driven rivets require the whole boiler to be hoisted and moved about at the riveting machine to bring each hole to the position required for the dies. Notwithstanding the trouble involved in handling and moving the boiler, it shows that it is possible to do ten times as much work, and with less skilled labor, by the employment of the riveting machine.
Calking.—One great source of danger in boiler making is excessive joint calking—both inside and out—where a sharp nosed tool is employed, and for the reason that it must be used so close to the inner edge of plate as to indent, and in many cases actually cut through the skin of the lower plate. This style of calking puts a positive strain upon the rivets, commencing distortion and putting excessive stress upon rivets—already in high tension before the boiler is put in actual use. It is, I hope, rapidly becoming a thing of the past.
With a proper proportion of diameter and pitch of rivet, all that is required is the use of a light "fuller tool" or the round-nosed tool used in what is known to the trade as the "Connery system."
There is but little need of calking if means are taken to secure a clean metal-to-metal face at the joint surfaces. When the plates are put together in ordinary course of manufacture, a portion of the mill scale is left on, and this is reduced to powder or shaken loose in the course of riveting and left between the plates, thus offering a tempting opening for the steam to work through, and is really cause of the heavy calking that puts so unnecessary a pressure on both plate and rivet. A clean metallic joint can be secured by passing over the two surfaces a sponge wet with a weak solution of sal-ammoniac and hot water, an operation certainly cheap enough both as to materials and labor required.
FIG. 19.
The above cut, Fig. 19, gives an illustration of calking done by sharp-nosed and round nosed tools, respectively. It will be seen by Fig. 20 that the effect of a round-nosed tool is to divide the plate calked, and as the part divided is well driven toward the rivets, a bearing is formed at a, from one-half to three-fourths of an inch, which increases the strength of joint, and will in no way cut or injure the surface of the under plate. A perfect joint is thus secured.
