Assessments - 5, GPA: 4.2
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Cutting beads quickly and accurately with the small skew is one of the most difficult lathe operations. Various working methods can be used . The first cut is a vertical incision at the point where the two curved surfaces will eventually come together. Make this cut with either heel or toe of skew. Fig. 47 shows the use of the toe. Place the skew at right angles to the work . The chisel is flat on its side at the start, and is evenly rotated through the successive stages of the cut (Figs. 48, 49 and 50). At the same time, the chisel is pulled slightly backward to maintain the cutting point. The entire cut is made with the heel of chisel. The opposite side of the bead is cut in the same manner, one cut serving to produce the full shape in each instance. This action produces beads that are beautifully smooth and polished, and the technique is well worth mastering. Fig. 43 Fig. 45A Fig. 46 Fig. 47 Fig. 49 Fig. 50 Fig. 44 Fig. 45B Fig. 48 17 VEE GROOVES Cutting the vee groove demands much the same technique as the bead, except the skew is hinged straight into the work without rotation (Fig. 51). Only one-half of the vee is made at a time, and one, two, or more cuts may be needed on each side to obtain the desired shape. As in all cutting with the skew, the bevel next to the cut must be used as a fulcrum. Be careful not to allow full edge of the chisel to catch and cause a run. Vee grooves can also be made with the toe of the skew, in the same manner as squaring an end. Fig. 51 Fig. 52 Fig. 53 Fig. 54 LONG CUTS Long cuts are usually either convex or straight-tapered surfaces. With a convex surface, the method used in making the finishing cut is shown in Figs. 52. The gouge is turned on the tool rest so that it will be inclined in the direction that it will move. The grind is tangent to the work, and the center point of the cutting edge is the contact point with the wood. As the cut progresses toward and around the end of the curve, the handle is gradually raised and swiveled to the right (Fig. 53) in order to maintain the tangency between the grind and the surface being cut . Figs. 54 and 55 show the cutting of a long taper with a skew. The operation differs from smoothing a cylinder only at the start of the cut. The starting cut should be made with the heel (Fig. 54) to prevent the tool from digging into the work. As the tool moves down the work, the chisel can be pulled back to allow the center point of the cutting edge to cut. However, the full taper can be made with the heel. Be careful not to cut too deeply at the center of the taper. The direction of cutting is always downhill. Fig. 55 COVE CUTS Second to forming a perfect bead, the cove or concave cut is the most difficult to master. This cut is made with the gouge, where the size of the tool depends on the size of the cut. Push the gouge directly into the work to remove the surplus stock (Fig.56). Fig. 56 18 The gouge is placed on edge on the tool rest so that the grind of the chisel forms an approximate right angle with the work (Figs. 57). The chisel contacts the work at the center of the cutting edge. Hold the tool so that the centerline of the gouge is pointing directly toward the center of the revolving stock. This starting position is important to prevent the gouge from running along the surface of the work. From the starting position, push the gouge into the revolving stock, and roll the tool on the rest. A triple action takes place here. (1) The chisel will roll to follow the shape of the cut, (2) the handle will drop slightly so that the portion already cut will force the lip of the chisel sideways and, (3) the chisel will be pushed forward so that at the end of the cut, Fig. 58, it will be well up on the work and tangent with the cut surface. Make only one-half of the cut at a time, then reverse the chisel to cut the other half. The occasional turner should make cove cuts with a scraping technique, using either the small gouge or round nose chisel. SQUARE SECTIONS When the turning has a square section, joint the stock before turning. Good centering is essential since any error will show at the shoulder where the round meets the square. Turning of the shoulder from square to round can be done in various ways. If the parting tool is sharp, the nicking cut with skew (Fig. 59) can be omitted. The final trimming operation (Fig. 62) can be done with either the skew, spear chisel, or gouge, and is a scraping operation. While the shoulder can be cut with the same technique used for cutting a bead, the simpler scraping method pictured does clean work and is easier to do. Fig. 57 Fig. 58 Fig. 59 Fig. 60 Fig. 61 19 Fig. 62 FACEPLATE TURNING Mount turnings that cannot be worked between centers on a faceplate. The greater part of this type of turning is done with the faceplate mounting, although there are a number of jobs which require special chucks. All cutting in faceplate work is done by scraping. Any attempt to use a cutting technique on the edge grain...
Este manual também é adequado para os modelos :Máquinas - 46-746 (1.42 mb)
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