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316 lake service is concerned, it is doubtful if the device woud find any very ex- tended use, inasmuch as the question is materially complicated by the hand- ling of water ballast. As is well known, the bulk carriers seldom have all their water ballast out before beginning to load, and, conversely, they almost in- variably have run in a_ considerable THE MarRINE REVIEW amount before the unloading is com- pieted, so that when the last bushel of grain or the last ton of coal or ore is out, the ship is immediately ready to leave port. Thus, either the handling of cargoes or handling of water ballast would have to be temporarily suspended while the other was going on, in order to make use of the porhydrometer. Lake Shipyard Methods of Steel Ship Construction By Rosert Curr. Reaming and Countersinking. HIS article deals with the work | on the ship after the plates and shapes are bolted up. On the great lakes after the plates and shapes have been properly bolted together a gang of men follow up and examine the holes, and those ae 66. unfair are reamed out so that a rivet fits into the hole, as shown by Figs. 66 and 67. Fig. 68 shows what might be termed a perfect piece of work ready for riveting and Fig. 69 same riveted up. Work of this kind is not always ob- tained which makes the perfecting of the work on the vessel by reaming and countersinking an important matter. Fig. 70 shows sections of plates punched and countersunk as they leave the shop. A, CG, E, G and I are the counter- sunk places, and B, D, F, H and-K are the punched plates. These plates when put together, if a perfect fit, will look like Fig. 67. The dotted line "a" shows the diameter of the holé of the drilled plates which is smal'er on the underside "a" than the actual rivet hole when punched as shown by the heavy lines. The hole when punched is larger on the under-. side of the plate because of the die being larger than the punch. This is governed by the style of rivets used. li they ate of the thick neck: type September, 1909 shown by Fig. 67 the die in the punch machine is made to correspond to same. The larger side of the hole is termed the burr side because it leaves a rough edge on the plate and makes it impos- sible to leave a close fit of the a4. terial when laid together. The putting together of the materials must be done by having the smooth surfaces laid to- gether. The materials which are _ counter- sunk may be punched with a very P76. GT large die thus making the countersink- ing much easier. Fig. 71 shows two p'ates riveted to- gether where the plates have been reamed out one-sixteenth of an inch and the rivet driven to fill the hole. The shaded part "A" shows a vacancy left because of the hole being punched with a die one-eighth of an inch larger than the punch. In order to have perfect work the hole should be reamed out a size larger and a larger rivet used as shown by dotied' lines C, D, E.. 1f the hole is a 12 | ut i} '© | ia 68.