In large power plants, mines, heavy and general machinery sector, many, such as aircraft seats, cylinder, pressure chamber and other parts needed large diameter hole (screw) process, and some large and deep hole, precision is also high, so that to substantially extend the machining cycle. Traditional high-speed steel drilling, reaming tool machining a large diameter hole, often 4 to 6 hours, or even longer, this backward processing methods and tools can easily become a production bottleneck.

To meet the rapid development of the production situation, research and development, application and efficient large-diameter tool it has become extremely urgent, and tool manufacturers at home and abroad and relevant research institutions to speed up processing of large-diameter hole cutting tool of innovation, research and development pace of the past few years have achieved encouraging results .

Currently processing large diameter hole (screw) machine tools are mainly two kinds: one is a large CNC boring, milling machine, lathe processing in such large diameter hole, due to machine power of large, rigid, high precision, general fitness can be used high-speed cutting of high-performance carbide cutting tools (particularly Indexable Carbide Hole Cutter); the other is common large-scale radial drilling machine, such machines while in power, rigidity, machining accuracy and so on can not be with large-scale CNC boring, milling, compared, but its biggest advantage is the low processing costs. At present the majority of heavy machinery factory will remain the main type of machine as a production and thus the development of large radial drilling machine adapted to the use of high-performance processing of large-diameter hole (screw) tool equally important.

A CNC boring, milling on the application of large-diameter hole machining tool

1.1 Drilling Tool

Cemented carbide / high speed steel drill large-diameter composite shows the typical structure of such tools, the tool cutting edge can be transferred from the carbide blade and high-speed steel center drill two parts. HSS center drill in the drill center, cutting speed is low, sharp blade and there is a smaller horizontal edge, so the axial cutting force is small, when cutting to stabilize drilling; drill on both sides of the indexable inserts cross arrangement, hardness and strength can be a better choice of blade and point-carbide chip-breaking groove (usually coated blade blade should choose), so that when the availability of drilling chips smaller C-shaped debris in order to facilitate cuttings the smooth discharge; drill pipe and drill bits are often used within the cooling structure, so that drilling will be well when the drill blade cooling, while cutting fluid under high-pressure injection pump chip can successfully discharge orifice; the tool arbor and Segment between the rings is also equipped with cross insurance, mainly to prevent the arbor in the overload of cutting damage.

Cemented carbide / high speed steel drill large-diameter composite

Using this high-performance large-diameter composite drill, cutting speed Vc of up to 80 ~ 120m/min, feed rate f of up to 0.1 ~ 0.12mm / r, the cutting efficiency and high-speed steel drills, expansion tool than can improve 8 ~ 12 times. The range of processing such drill in general? 80 ~? 170, the machine power permit conditions, or even can be processed? More than 300 big hole. The current drill in the domestic Harbin Steam Turbine Factory, Shanghai Lung Kee Metal Co., Ltd. and other units have been widely used.

1.2 Nesting carbide indexable drill

Nesting drilling structure diagram shown in Figure 2, the tool design, manufacture high precision, there are three groups of knife blocks, each block of two knives symmetrically distributed in the cutter body, the third group with eccentric clamp, first, two groups using the slider eccentric clamping, two blocks of height difference between adjacent group cutter 0.25 ~ 0.30mm, the same set of two blade height are equal, since the role of a good sub-crumbs. 45 # steel cutting, the cutting fluid is oil, oil pressure P is 0.5 ~ 0.7MPa. Present Carbide Indexable-drill holes in Shanghai, Shen Machinery Factory has stabilized applications, and achieved obvious results of processing.

Internal thread cutting tool

Efficient processing of large-diameter internal thread, the tool applications more structural form in two ways.

Whirling large-diameter internal thread cutting head of the milling head is an independent technology and equipment belong to machine tool accessories. It applies to the ordinary screw feeding system with a horizontal boring, milling and other machines on the thread milling process, milling head can be installed 1 to 4 indexable threaded inserts, cutting tools in high-speed rotation circle milling, while also carried out feed and axial feed (ie, spiral feed), the additional cyclone-type internal thread cutting head's structure shown in Figure 3, the device is commonly used rice M30 ~ M120 system and 1.5 "~ 4.5" threaded hole of the British the left and right thread whirlwind milling.

Carbide Thread comb knife This is a newly developed in recent years, a highly efficient internal thread processing tool, the knife blade can be a single head, it can be a multi-chip. As the blade pitch is fixed, so the same kinds of specifications of the blade pitch applied to a variety of different diameters with a large screw holes machining. Carbide coated screw comb-type blade in order to choose the better choice of cutting speed is generally 100 ~ 120m/min, application of the tools available to the big thread processing efficiency, high-quality processing results. Deep in the processing thread, it often occurs due to such factors as Arbor vibration chatter and hole deflection, this time with anti-vibration performance can choose arbor to be addressed. At present, the type of tool in Beijing Heavy Electric Machinery Plant, the first heavy plant and Shanghai Hudong Shipyard vehicle applications, and other units. Schematic diagram of the tool can be seen

In the radial drilling machine on the efficient processing of large-diameter hole cutter

2.1 high-speed steel drill large-diameter flat

This is a hole in the most primitive kind of machining tool, because of its manufacturing simple, easy to use, small and medium non-standard in the previous single hole, a small group of part machining has been widely used, but the cutting efficiency is low, tool life is short, hole machining defects and poor quality, limiting the development of such tools. In recent years, due to domestic needs in a large radial drilling large diameter holes on the processing of an increasing number of parts, which require high performance for large radial drilling machine drilling tool is also increasing calls for the development of innovative high-bian can drill further improvement of a highly efficient tool hole processing also mentioned on the agenda. The relevant units at home and abroad through research, improvement, development, now large-diameter flat drill has been successfully applied to domestic and foreign heavy-duty business-to-part machining large diameter holes. Its innovative cover mainly the following: Tools folder structure, using blade type, arbor with coolant holes, cutting the role of high-pressure coolant, the blade may be fully cooled down; blade selection of high-performance materials, high-speed steel (such as the M42, etc.) and the surface coating; reduce the horizontal edge and an appropriate tool increase the tool rake angle, so that the axial cutting force reduced; both sides of the blade to increase cross-sub-flute (with the rake face of the chip-breaking groove and reasonable walk the knife volume), so that chip into a C-chip, to facilitate discharge and reduce the cutting resistance. A typical large-diameter drill hole flat structure diagram shown in Figure 5.

Harbin Electrical Machinery Plant are now many products for all the application components hole processing of this large-diameter flat drill, to achieve an efficient cutting.

2.2 high-speed steel drill large-diameter composite

High Speed Steel Machine folder structure as the large-diameter composite drill within the cooling type, and the carbide / high speed steel composite drill different places are: the original on both sides of the cutter head used in carbide indexable inserts into both sides with a sub - slot 2 chip blades, high-performance high-speed film; pairs of blades were enhanced surface treatment (coating or multicomponent permeation treatment); in the tool geometry is processed materials were made on the basis of different options. At present the types of high-speed steel drill large-diameter composite applications in Harbin Steam Turbine Plant, its processing efficiency than the original high-speed steel drills, reaming tool increased three times more than the same time, there was a marked increase tool life and can significantly shorten the loading and unloading, Grinding tool time.

2.3 The large-diameter internal thread cutting tool

Large diameter and steep helix angle tap machining large diameter threaded hole within the traditional practice is to use tap set into groups to complete, but because of application of multi-vessel tap processing, and spindle runout often easy to cause vibration, easy to screw processing appears corrugated, " double-fold ", thread-pass-side unreasonable only Tuanthong and so on. The large-diameter spiral flute tap tap tapping a single branch is made when the chips tapping smooth continuous discharge, with very little resistance; Also, such a tap there is a large spiral angle (35 ° ~ 40 °), can be to increase the actual capacity of debris before the angle and space, cutting torque, so that cutting is more stable and help to improve processing efficiency and quality assurance, its tool structure diagram shown in Figure 7, usually large helix angle tap the scope of application of M56 ~ M140.

The contents of the contents of chip crumbs Taps Taps is an advanced and efficient processing of tap, both as applied to CNC boring and milling machine for large diameter internal thread hole processing, but also for large radial drill the hole on the processing thread.

The main features of the content of crumbs tap are: the capacity of ordinary tap flute axial grooves, while the content of the capacity of chip flute tap is a tap to open the front there is a large enough storage capacity chip crumb pore space; content crumbs Taps work in part by thread composed of three parts, in the cutting cone of thread from the role of rough-cut, cylindrical thread on the break from the standard role in the integrity of screw thread on the cylindrical guiding role played; the content of crumbs on the opening tap of the cutting cone has brought the left are Cutting edge inclination of the cutting edge, Tapping into the front when the cuttings, so tap back, it will not get stuck due to the phenomenon caused by the chip, when the processing of blind hole, the chips are stored in the capacity of debris hole, chip and being processed thread the surface completely isolated, and therefore the ideal chip disposal, so that thread surface quality can be improved.

Nested content processing chip tap the range of M56 ~ M250, cutting speed Vc is processed according to different materials are often used in 2 ~ 6m/min, general machining accuracy of up to 6H. At present, the content of such high-performance chip TAP has been in the domestic steam turbine, generators, industry and promote the use of heavy machinery manufacturing industry.