Évaluations - 5, GPA: 4
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Facilité d'utilisation
This tool is used for smoothing cylinders, for cutting shoulders, beads, vee-grooves, etc. The spear or diamond-point chisel and the round-nose chisel are scraping tools which are used where their shape fits the contour of the work. The parting tool is a double-ground chisel, and is used for cutting-off and for making straight incisions or sizing cuts to any required diameter. Cl Î w GOUGË ; SKEW SPEAR; GOUGE PARTING RP.NÔSE GOUGE SKEW Fig. 27 Fig. 28 13 Fig. 29 CENTERING THE WORK Wood stock for any spindle turning should be approximately square, and the ends should be square with the sides. Two common methods of determining the center are shown in Fig. 30 and 31. In Fig. 30 a distance a little more or a little less than one-half the width of the stock is set off from each of the four sides. The small square thus set off in the center can then be used in marking the true center. The diagonal method, Fig. 31, consists of drawing lines from corner to corner, the intersection marking the center of the work. After marking each end, the true center should be definitely marked with a punch awl or dividers, as shown in Fig. 32. If the stock is hardwood, the centers should be drilled to a depth of about 1/8”, as shown in Fig. 33. The spur or live center is then placed against one end of the work and seated by striking with a mallet, as shown in Fig. 34. In hardwood, it is advisable to make a starting seat for the spur center, this being done by sawing on the diagonal lines, as shown in Fig. 35, and drilling a small hole at the intersection. After driving the center, it is best to hold center and work together and fit immediately to headstock spindle. If you are not using a ball bearing center, the end of work at tailstock center should be oiled, placing the lubricant on the wood either before or after it is put in the lathe, see Fig. 36. Many turners use beeswax, tallow, or a wax-and-oil mixture as a lubricant, The ideal method is to use a ball bearing center, which eliminates lubricating entirely. If the work is to be removed from the lathe before completion, an index mark should be made as a guide for recentering, as shown in Fig. 37. A permanent indexer can be made by grinding off one corner of one of the spurs. Fig. 30 Fig. 31 Fig. 32 Fig. 33 MOUNTING THE WORK Mounting the work is done by moving the tailstock up to a position about 1 or 11/2” from the end of the stock, and locking it in this position. Advance the tailstock center by turning the feed handle until the center makes contact with the work. Continue to advance the center while slowly rotating the work by hand. After it becomes difficult to turn the work, slack off on the feed about one-quarter turn and lock the tailstock spindle. 14 TOOL REST POSITION The tool rest is now mounted, in place, about 1/8” away from the work and 1/8” above the work centerline, as shown in Fig. 38. This position may be varied to suit the work and the operator. A guide mark to show the most suitable working position can be placed on the tool rest shank as an aid to quick and accurate re-setting. Once some experience has been obtained, the setting of the tool rest will become almost second-nature. ROUGHING A CYLINDER The large gouge is used in the first turning operation of roughing-off the sharp corners of the work. Run the lathe at low speed and hold the gouge in the manner shown in Fig. 39. The cut starts about 2 inches from the tailstock end, and continues from this point towards and off the tailstock end. A second bite is then taken about 2 or 3” to the left of the first cut, advancing again towards the tailstock to merge with the cut previously made. The procedure continues until a point about 2” from the live center is reached where the gouge is rolled in the opposite direction to carry the final cut off the live center end of the work. The roughing cut should not be carried out with one continuous movement as this tends to tear long slivers from the corners of the work; neither should the cut be started directly at the end of the stock for the same reason. The cut can be safely carried from the center of the stock towards and off either end once the first roughing cut has been made. The position of the gouge in relation to the work involves two or three important angles. First of all, the tool may be advanced along the work either from right to left or from left to right. From left to right or from headstock towards tailstock is preferable, since this throws the chips clear of the operator. The gouge is rolled over slightly in the same direction it is advancing, as shown in Fig. 40. The tool is held well up on the work, with the bevel or grind tangent to the revolving surface, as shown in Fig. 41. In this position it will make a clean, shearing cut. When pushed straight into the work, like Fig. 42, the gouge has a scraping action, which is normally poor practice in spindle turning. The roughing cut is continued until the work approaches 1/8” o...
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