File:Canadian forest industries 1897-1899 (1899) (20517788712).jpg

Title: Canadian forest industries 1897-1899
Identifier: canadianforest189799donm (find matches)
Year: 1899 (1890s)
Authors:
Subjects: Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries
Publisher: Don Mills, Ont. : Southam Business Publications
Contributing Library: Fisher - University of Toronto
Digitizing Sponsor: University of Toronto

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14 THE GJL1XJLIDJL LUMBERMAH April, 1899 of the thickness of the fibres, and is difficult to remove from the wet machine, as the sheet will not hold together. When a stone has been over-sharpened by carelessness or otherwise, it may be restored by simply rubbing the surface with a brick. Some pulp makers prefer to sharp- en this way, i.e., by over-sharpening at first and then re- ducing the cuts on the stone, by means of a brick, until the right degree is reached. " A very good point in the construction of a grinder is to have the stone accessible while in operation. Some machines have to be stopped and certain alterations made before the stone can be sharpened. While this is being attended to, the opportunity is generally taken to clean them out, and in this way the disadvantage of not being able to sharpen while running is in some manner counter- acted. The sharpening jig is a cylinder of steel, about 3^ of steel, one on each side of it. These flanges are turned true on their face and are threaded right and left hand on the shaft. By this method the torsional strain on the stone due to the grinding tends to make the flanges grip tighter. There are two principal methods of securing the stone to the shaft, one being an improvementon the other. The first method is to screw the flanges up as tight as possible, taking care that the stone is centered, and then to pour in cement around the shaft and flanges, through a small channel which had been previously cut in the stone. This method is in use in the majority of cases and seems to answer the purpose very well. The second method is very much like the first, butjn addition to the cement and threaded flanges, the flanges are bolted toge- ther by i-inch bolts, running through the stone from side to side, which are tightened up before the(cement has be-
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turned down to the required size, and made true on its face. It is best in turning off a stone to make the face slightly crowned or else to turn down near the edges more than at the centre. This prevents to some extent the spauling of the stone from the pressure of the wood. Great care must be taken that in turning down the stones no cracks are made in it, for, if any exist, the piece will very likely fly out when the pressure is applied. This, of course, will ruin the stone eventually, even if it is a small piece, as when one piece is broken out, others quickly follow. It is bad practice to run a stone after it has been spauled. In handling the stone when bringing it into the mill, it should, if possible, be slung from a carrier by ropes passing through its centre hole. As this is not provided for in many mills, the next best thing is to roll it on strong palnking, taking care that it is only bearing in the middle of the face and not near the sides. It should, in all cases, be eased by ropes and blocks, so as to have it at all times under control. If care is taken, a stone can be mounted without the edges becoming spauled more than will be completely removed by turning down and trueing. Description of Screens.—When the pulp and water leave the grinder, it flows along the troughs placed un- derneath the floor of the grinder room to the large trough, into which every grinder discharges. In this large trough are sprays, which supply sufficient water for the pulp to flow along it. At the end of this trough is placed a large tank covered over with iron plates, which are perforated Fig. 10.—Vibrating Diaphragm Pulp Screen (Manufactured by Jenckes Machine Co.) inches long by 3 inches in diameter. It is cut on its sur- face by a heavy V thread, and also milled paralled to its axis by an equally heavy V cut. The resulting surface consists of a number of square, sharp-pointed pyramids. The jig is drilled throughout its length with a i-inch drill, and mounted in a frame by a bolt passing loosely through this hole, so allowing it to revolve freely thereon. The frame also has on it a forged ring, which is made to en- gage a bolt on the grinder frame. This bolt passes across the face of the stone, and a few inches from it. The frame has also a suitable handle, by means of which it is guided by the workman. In operation, the bolt is passed through the ring and secured in the grinder frame. The workman can now girdle the jig across the face of the stone, against which it revolves. By bearing on the handle the pressure is applied, which causes the points of the jig to cut the face of the stone, making on it a rough pitted surface. Method of Changing and Mounting Stones.—The stone is secured to the shaft by means of large flanges come hard. When the cement has set perfectly hard the stone can be turned off and trued up. The addition of the bolts in the second method adds considerably to the strength and solidity of the whole machine as well as pro- viding a safe-guard against bursting. For this purpose alone, it would almost be advisable to introduce them. Setting Stones.—When the stone is set in, it is very irregular on its surface, and must be turned off true before using. For this purpose an attachment is used which in its motions resembles the slide rest of a screw cutting lathe. It consists-of a frame, which is placed on the grinder base, where it is bolted down firmly. On this frame there runs a carriage which is moved laterally across the face of the stone by means of a screw and hand wheel. Mounted on this carriage is a similar one, which moves at right angles to the surface of the stone, and is actuated also by a similar screw and hand wheel. On this top carriage is fitted a jig, similar to that used in sharpening, though generally a dull one is selected for turning off a stone. With this machine a stone can be

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