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Diamond drill iron group characteristics and use

2016-03-05

From Table 5-2, gray cast iron (eg HT20-40) may Drilling rating of 3,4,4,3, which belongs to a class of easier drilling. But in terms of its four indicators, Ⅱ, Ⅲ high indicators that plastic is low, cutting chipping, thermal slow, the heat concentrated in the cutting edge. Thus, the basic strategy is:

(1) drill through the workpiece should be as short as possible from the cutting edge with the workpiece in contact as soon as possible, reducing the chance of drill cutting edge with the workpiece friction. The so-called fast through the workpiece, is to ask drill feed amount as large as possible per minute, that is the speed (n) and feed rate (f) the product of (nf mm / min) to large. On the other hand, when the bit depth per minute drill is the same, namely the feed stroke (nf) per minute is constant, since the cutting edge is along the helix forward, if turn slowly (n small), feeding faster ( f large), the helical pitch of the large number, the cutting edge is shorter total distance traveled, the cutting edge by the friction opportunity reduced. Therefore, we should increase the feed rate as far as possible, and then select the appropriate speed.

(2) to increase the feed rate, the drilling resistance increases, so should the drill bit sharp as possible. Since drilling cast iron axial resistance is a major part of the axial resistance focused on the addition of cross-edge, therefore, reasonable grinding drill chisel, to reduce the axial resistance are important. If the chisel completely removed, the axial resistance can be significantly reduced, but this raises two issues: first, the centering is bad, usually use a jig to locate; the second, when drilling hard cast iron, especially When the little black and white face has casting, chipping drill easily. It should not be completely worn chisel should retain some terrible tip, but drilling group than the drill steel chisel repair worn narrower, sharper some γτ0 front inner edge angle can be larger.

(3) In order to protect the terrible tip, grind sharp crescent arc groove so terrible low down soon after plunging into the workpiece while cutting three sharp, terrible tip easily collapse and wear, but also to facilitate alignment. While cross-edge repair more narrow, but highly drill tip drill steel and basic similar.

(4) double front corner. Due to the outer edge of the drill cutting height, ie the relative friction velocity high, so that the drilling portion generates heat, combined with cast iron heat conduction slow, so the heat is concentrated on the outer edge of the blade at the tip of the drill bit, resulting in the fastest wear it. Typically, grind chamfer, which form a double edge angle (2ψ1), so that the corner widened, improved drill thermal conditions, thus improving the durability. After numerous experiments, it showed double front angle can improve the durability of 2-4 times, as shown in Table 5-5. However, due to grind dual front corner, lengthen the cutting edge, so that the drilling torque increased slightly. However, reducing the axial force drill a lot of cast iron drilling group, torque increase is not much, so the total cutting load is small.

(5) appropriate to increase the posterior horn. Generally larger than the drill steel 3. So, after reducing friction between the drill and the workpiece flank. According to the results, after αfc outer edge angle of 13 to 18. When higher bit durability.

(6) the rational use of cutting fluid. Some people in the drilling of cast iron parts, reluctant to use cutting fluid. There may be some objective factors, such as a large piece, cutting fluids difficult to clean; debris containing graphite water quickly becomes dark and dirty and the like. But for large quantities of drilling processes, better use of cutting fluid, which can greatly improve the durability of the drill bit, drilling to improve quality, and avoid dust flying. But pay special attention to cutting fluid should be added continuously throughout, and flow should be appropriate, or a small amount of water into the hole and intermittent, likely to cause localized hardening hole wall, and the debris reconcile into a grinding paste as increased drill bit wear.

(7) When they find "bar knife" phenomenon, the need to take appropriate measures section.

(8) The amount of the selected group of cutting drill cast iron, you can refer to Table 5-6.

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