Slot cutters

Small complex tool steel parts are being made by conventional compaction and sintering in vacuum to near theoretical density. AppHcations include spade drills, knife blades, slotting cutters, insert blades for gear cutters, reamer blades, and cutting tool inserts. 

Milling Staggered-tooth Angle T-slot cutter T-slot... 

T-slot cutter Woodruff keyseat cutter Form milling cutter... 

Designed for milling tee slots in machine tables, this cutter has teeth on its circumference and on both sides. To reduce chatter and provide maximum chip clearance, the teeth are alternately right-hand and left-hand helix, and each alternate side tooth is removed. To produce a tee slot, the groove is first cut using a side-and-face cutter, end mill or slot drill and finally the wide slot at the bottom is cut using a tee-slot cutter. Fig. 11.8(k). The shank is reduced to clear the initial groove. This cutter is available for standard tee slots to suit bolt sizes up to 24 mm. 

By using the theory and method discussed in the literature," the stability charts shown in Fig. 1.19 (rows I) are obtained. It must be stressed that these are valid for a particular machining process specified by the geometry of the tool/workpiece and the material properties, as specified in Table 1.2. Both relate to the bonded machine. Fig. 1.19(a) for machining with a slot cutter and Fig. 1.20(a) when a helix cutter is used. 

Fig. 1.19. Theoretical and experimental stability charts of bonded machine with slot cutter, (a) Theoretical stability chart = 0-63 X 10" N/jum/jum C = 0 0021 Zc = 2). (b) Experimental stability chart.

Results reported so far correspond to the slot cutter specified in Table 1.6, and used in previous work. However, tests performed by machine-tool markers generally follow the recommendations of the Machine Tool Industry Research Association (MTIRA), and these involve the use of a helix cutter. As pointed out, with the slot cutter the limiting factor of machine performance is the onset of chatter, while with the helix cutter it is both the onset of chatter and the available driving horsepower. It is clearly of practical interest to establish whether the theory of chatter allows the prediction of the stability for both types of cutter. 

With these data, and those in Table 1.6, the stability chart was calculated and it is presented in Fig. 1.20(a), row I. Note the very much greatervalueof IFmoi = 24-8 mmandlF o2 = 3-5 mm compared to those obtained in the case of the slot cutter (Fig. 1.19(a)). However, the two stability charts are not comparable since they correspond to different values ofz and d/R (Table 1.6). As far as the d/R ratios are concerned, the very much smaller value of the helix cutter was necessary since otherwise the available drive power would have been exceeded, as will be seen from the experimental results. 

The geometry of the test pieces can be seen from Fig. 1.22. Figure 1.22(a) was for the slot cutter tests, allowing a deep depth of cut but requiring only a small width. Figure 1.22(a) gave a very fast variation for the width of cut which with some tests caused inaccuracies, and therefore in these circumstances the test piece shown in Fig. 1.22(c) was used. 

Fig. 1.22. Specimens for cutting tests, (a) Slot cutter, (b) Helix cutter (large width), (c) Helix cutter (small width).

In Figs 1.19(b) and 1.20(b) the top row shows the variation of the power consumption. Note that, for the slot cutter in the speed range up to zN = 2200 tpm, the range of the first set of unstable lobes, the power consumption varies between 10 and 1-2 hp. For the speed range of the second set of unstable lobes, the power consumption is between 1 and 1-3 hp. Clearly, the slot cutter does not load the drive motor of the machine anywhere near to the maximum capacity of the driving motor. 

Figure 1.17(b) shows the direct and cross receptances of the cast-iron machine. From these the operative receptances are found, presented in Fig. 1.18(c) for the slot cutter and Fig. 1.18(d) for the helix cutter. The particular conditions to which these refer are specified in Table 1.6. 

A wide variety of mechanical devices are now in use and include flow-through cutters, bucket cutters, reciprocating hoppers, augers, slotted belts, fixed-position pipes, and rotating spoons. These systems typically collect the primary increments and perform at least part of the sample preparation by crushing and dividing it down to the 4- or 8-mesh stage of reduction specified (ASTM D-2013). 

Measurements of milled grooves using a coordinate measuring machine clearly show the form deviations of the slot flanks. Figme 3 shows the exaggerated flank forms of slots milled with a 2-teeth cutter and with a 3-teeth cutter. 

Looking at Figs. 2 and 4, it can be clearly seen that the tools do not have a rectangular outline. The slot flanks are machined oidy by short sections of the cutting edges at a time. In the case of a 3-teeth cutter, these short sections are at different heights. This is the reason why a slot milled with a 3-teeth cutter is not symmetric. 

Now the theoretic profile of the slot in a plane is known (without considering forces). As the milling cutter is rotating and moving forward, the points PI, P2, P3, and P4 are moving upward and forward. So the scallops are tilted by the angle a (Fig. 11). 

This cutter has teeth on the periphery or face and on both sides. It is used to produce steps, cutting on the face and side simultaneously. Fig. 11.8(b), or for producing slots. The use of these cutters in pairs with their sides cutting is known as straddle milling. Fig. 11.8(c). The teeth are straight on cutters up to 20 mm wide but are helical above tbis thickness. Side-and-face cutters are available in a variety of sizes up to 200mm diameter and 32 mm wide. 

More often referred to as a shell end mill . Fig. 11.8(h), this cutter has teeth cut on the circumference and on one end. The tooth end is recessed to receive a screwhead for holding the cutter on an arbor. A key slot on the back face provides the drive from two keys in the arbor. The... 

This cutter has helical teeth on the circumference and teeth on one end and is used for light operations such as milling slots, profiling and... 

Usually having two or three helical teeth cut in the circumference and teeth on the end, cut to the centre, this cutter can be fed along its own axis in the same way as a drill. It is used to produce keyways and blind slots with the cutter sunk into the material like a drill and fed longitudinally the length of the key way or slot, cutting on its circumference. Fig. 11.8(j). It is available in a variety of sizes up to 50 mm diameter. 

Cutters which are used close to the spindle, such as shell end mills, are mounted on a stub arbor. Fig. 11.10. This arbor is located, held, and driven in the spindle in the same way as a standard arbor. The cutter is located on a spigot or stub and is held in position by a large flanged screw. Two keys on the arbor provide the drive through key slots in the back face of the cutter. 

Large face mills are mounted directly on the spindle nose. To ensure correct location and concentricity, a centring arbor with the appropriate international taper is held in the spindle by the drawbar. The diameter on the end of the centring arbor locates the cutter, which is driven by the spindle keys through a key slot in the back face of the cutter. The cutter is held in position by four screws direct into the spindle nose. Fig. 11.12. 

FIGURE 8.3 A slotted-belt secondary cutter. (From Meyers, R.A., Ed., Coal Handbook, Marcel Dekker, New York, 1981.)... 

Cutter cutting machine A machine, usually used in coal, that will cut a 10-15 cm slot, which... 

A staggered-tooth side-and-face cutter, also having teeth on the periphery and on both sides, is designed for deep-slotting operations. In order to reduce chatter and provide maximum chip clearance, the teeth are alternately right-hand and... 

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