Jewels That Wear Out In Service

Sun (Auckland), Volume 1, Issue 47, 18 May 1927, Page 1

Jewels That Wear Out In Service

Diamonds Help to Build War Museum STONE-MASONS' CRAFT Introducing the diamond which works -for its living by helping to shape Portland stone for the ne w War Memorial Museum. In the stone yard at the back of the Museum building, which is now comD lete to the cornice, circular saws are ripping into th,i hard Portland blocks, .shaping them for their specified places in the scheme. The teeth of the saws are not steel, which would wear out very quickly, but diamonds, black Brazilian ones, costing about £2 5s each. They eat in at the rate of three to six inches a minute, streams of water being forced into the cuts in the stone. If it were not for this cooling influence the jewels would simply melt away. Each diamond wears itself out in about twelve months of service, and has to be replaced. The large single-blade machine carries 120 jewelled teeth and the smaller twin-bladed one has a total of ICO. HANDLING 15-TON BLOCKS Blocks of stone weighing up to 15 tons are swung into position in the yard, which contains probably the iargest stone-working plant in Australasia, by electric conveyors, one of which can lift '2O tons. The first breaking down is done by one of the older type of 3teel saws. This works on the cross-cut idea, long steel blades working backward and forward over tine steel shot and cutting through the stone at the rate of from six to ten inches an hour. It has the advantage that up to 12 cuts may be made at one time in a block. The blades would wear themselves to shreds in an hour if they did net work on the shot and if water did rot run on them. POLISHING THE STONE Like a gramophone turn-table is the polishing machine, in which an iron disc 12 feet in diameter turns underneath the fixed blocks of stone. Finer polishing is done by a machine which holds a disc of carborundum on the surface and the moulding and shaping of corners is also carried out by means of curiously shaped blocks of carborundum. Twenty-three masons and machine men are at work, under Mr. J. Tweedie, in the stone yard of the Hansford Mills Construction Co., the contractors for the museum. One of the blocks of Portland stone in the yard has a history and it will be placed in the museum proper. It was quarried at the order oi Sir Christopher Wren, when he was building St. Paul’s, after the Great Fire of London, 250 years ago. It still bears the quarry mark.