Wharbo Precision Manufacturing Co.,Ltd

First, drilling and reaming

1. Drilling

Drilling is the first step of making a hole on a solid material when machining, hole diameter generally less than 80mm. Drilling in two ways: one is the rotary drill bit; the other is the workpiece rotation. Both the drilling mode error generated is not the same in the rotating drill bit mode, since the cutting edge asymmetry and lack of rigid drill bit when leaving the lead side, the hole will be processed centerline skew or not straight, but essentially the same pore size; and the rotation of the work in the opposite way to the borehole, the drill bit will cause the primers partial aperture variation, while the axis of the hole is still straight.
Commonly used drilling tool are: twist drill, center drill, deep hole drilling, the most commonly used is the twist, the diameter specifications for Φ0.1-80mm.

Due to restrictions on the structure, bending stiffness and torsional stiffness of the drill were lower, coupled with a bad disposition set lower precision drilling, generally only reach IT13 ~ IT11; surface roughness is larger, Ra is generally 50 ~ 12.5μm; but drilling metal removal rate, high cutting efficiency. Mainly used for processing low-quality drill holes, such as bolt holes, starting hole, the hole and the like. Machining accuracy and surface quality for demanding holes, it should in subsequent processing by reaming, boring or grinding holes to achieve.

2. reaming

Reamer reaming is already drilled, cast or forged out of the hole for further processing, in order to expand and improve processing quality aperture hole, reaming process can be used as a pre-processing finishing holes in the front can also be used as less demanding final hole machining. Reamer with a twist similar, but the knife too many teeth, no chisel edge.

Compared with drilling, reaming has the following characteristics: (1) the number of teeth reamer multiple (3-8 teeth), the guide is good, cutting more stable; (2) there is no chisel edge reamer, good cutting conditions; (3) allowance smaller chip flutes can be made shallow, core drilling can be made thicker, better strength and rigidity cutter body. Reaming precision machining is generally IT11 ~ IT10 level, surface roughness Ra of 12.5 ~ 6.3μm. Reaming commonly used in the processing of a smaller diameter than the hole. Drilling large diameter holes when (D ≥30mm), often first with a small drill (pore diameter 0.5 to 0.7 times) pre-drilled holes, and then use the appropriate size reamer reaming, this can increase the hole processing quality and production efficiency.

In addition to machining cylindrical bore hole expansion, you can also use a variety of special shapes reamer (also known countersink drill) to process a variety of sink holes and countersink flat headstock end face shown. Countersink drill tip often with a guide column with machined hole guide.

Second, reaming

Reaming is one method of finishing the hole, in the production of very wide application. For smaller hole, with respect to the inner circle in terms of grinding and fine boring, reaming is a more economical processing methods.

1. Reamer

Reamer is generally divided into hand reamer and machine reamers two kinds. Hand reamer shank straight shank, longer working portion, the guiding role of good hand reamer with integral and outer adjustable two structures. Machine reamer shank and has two structures jacketed. Reamer can process not only circular holes, can also be processed taper reamer cone.

2. reaming process and application

Reaming reaming margin a significant impact on the quality of the margin is too large, reamer load, cutting edge soon be blunt, is not easy to obtain smooth machined surfaces, dimensional tolerances are difficult to guarantee; margin is too small, indelibly marks left on the step, naturally there will be no improvement hole machining quality. Usually crude hinge margin is taken as 0.35 ~ 0.15mm, precision hinge taken as 01.5 ~ 0.05mm.

To avoid BUE, reaming usually lower cutting speeds (high speed steel reamer machining steel and cast iron, v <8m / min) for processing. Feed rate and the value to be processed concerning aperture, the larger the aperture, the greater the value of the feed rate, feed rate of high speed steel reamer when machining steel and cast iron is often taken to be 0.3 ~ 1mm / r.

Need for cooling, lubrication and cleaning with a suitable coolant when reaming to prevent BUE and timely removal of chips. Compared with grinding and drilling holes, reaming, high productivity, easy to guarantee the accuracy of the hole; but the position error can not be corrected reaming bore axis, the positional accuracy of the hole should be guaranteed before the process. Reaming should machining stepped holes and blind holes.

Reaming dimensional accuracy is generally IT9 ~ IT7 level, the surface roughness Ra is generally 3.2 ~ 0.8 μm. For medium-size, high precision holes (for example IT7 level precision hole), drill - expanding - hinges used in the production process is the typical processing scheme.

Third, boring

Boring holes in the pre-cutting tool so as to expand a processing method, boring work either on a boring machine, can also be carried out in a lathe.

1. boring way

Boring There are three different processing methods.

(1) rotating the workpiece, the tool feed movement as lathe boring most boring part of this approach. Process characteristics are: consistent with the axis of rotation axis of the workpiece machined hole, roundness of the hole depends on the accuracy of rotation of the spindle, the axial hole geometry error depends on the tool feed direction with respect to the rotation axis of the workpiece positional accuracy. This boring manner suitable for processing with the cylindrical surface of the bore concentricity requirements.
(2) rotation of the tool, the workpiece spindle for feed movement driven boring boring tool rotates the workpiece table drive for feed movement.

(3) for rotation of the tool and feed movement with this boring way boring, boring bar overhang length is varied by deformation of the boring bar also varies, close to the headstock at large aperture, away from the headstock at a small aperture to form a tapered bore. In addition, the boring bar overhang length increases, the spindle due to bending deformation caused by the weight increases, the hole axis machining will produce a corresponding bending. This drilling method is only suitable for processing short holes.

2. Diamond Boring

Compared with the general Boring, boring Diamond is characterized by a small knife to eat the amount of the back, a small amount of feed, cutting speed is high, it can get very high precision (IT7 ~ IT6) and a very smooth surface (Ra 0.4 ~ 0.05 μm). King Kong boring first boring tool with diamond processing, it is now widely used carbide, CBN and synthetic diamond tooling. Mainly used for processing non-ferrous metal workpieces can also be used for machining cast iron and steel.

Diamond boring conventional cutting amount: knife back to eat the amount of pre-boring is 0.2 ~ 0.6mm, the final boring of 0.1mm; feed rate is 0.01 ~ 0.14mm / r; cutting speed when machining cast iron 100 ~ 250m / min, machining when the steel is 150 ~ 300m / min, the processing of non-ferrous metals is 300 ~ 2000m / min.

In order to ensure the diamond drilling can achieve high machining accuracy and surface quality, the use of machine tools (diamond boring) must have high geometric accuracy and rigidity, precision machine tool spindle bearing common angular contact ball bearings or hydrostatic slide bearings, high-speed rotating parts subject to precise balance; in addition, the feed mechanism must be very smooth motion, to ensure smooth low table do feed movement.

Processing quality of diamond drilling, high production efficiency, a large number of mass production is widely used for the final machining of precision holes, such as engine cylinder bore, the piston pin hole spindle bore spindle box and so on. But attention is required: the processing of ferrous metal products with a diamond drilling, the use of carbide and CBN only made boring tool can not be made using a diamond knife boring, because the affinity of carbon atoms in diamond and iron group elements large tool life is low.

3. Boring Tool

Boring tool can be divided into single-and double-edged knife blade boring boring tool.

4. Boring process characteristics and application scope

Boring and drilling - expanding - hinges process compared to the size of the tool unrestricted aperture size, and bore a strong error correction capability, can pass through several amendments to the original bore axis skew errors and allows the bore and locating surface maintain high positional accuracy.

Car cylindrical bore and compared the difference between the system due to the rigidity Arbor, deformation, cooling chip bad conditions, thermal deformation of the workpiece and the tool is relatively large, processing quality and productivity are not as boring car cylindrical high .

The foregoing analysis shows that processing a wide range of boring, can process a variety of different sizes and different levels of precision holes, for larger pore size and location of high precision holes and holes, bore almost the only processing method. Precision boring of IT9 ~ IT7 level. Boring can be on boring machines, lathes, milling machines and other machine tools, has the advantage of flexible, production is widely used. In a large number of mass production, to improve the efficiency of drilling, boring mode is often used.

Fourth, the hole honing

1. Principles and honing honing head

Honing honing head with the use of the bars (Whetstone) method of finishing holes. When honing, the workpiece fixed and honing head spindle and rotated by a reciprocating linear motion. Honing process, the bars with a certain pressure is applied to the surface, a very thin layer of material removed from the workpiece surface, which is cross-cutting path textured. To make abrasive sand bar trajectory will not be repeated, the number of revolutions per minute honing head rotary motion and reciprocating stroke honing head per minute into each other should be a prime number.

Honing track crossing angle and speed and the peripheral speed of the reciprocating honing head is related to the size of the impact angle of honing processing quality and efficiency, and generally ° when coarse honing, fine honing take time. In order to facilitate the discharge of broken grains and chips, reduce the cutting temperature and improve processing quality, honing should use plenty of cutting fluid.

In order to be processed cell walls can get a uniform processing, sand bars at both ends of the hole must travel beyond the period of overtravel. In order to ensure uniform honing margin, reduce the impact of errors on the rotary spindle machining precision, mostly using between honing spindle head and floating connection.

Radial grinding honing head of the telescopic adjustment of a variety of structural forms manual, pneumatic and hydraulic pressure and the like.
2. Process characteristics and application range of honing

1) honing obtain a higher dimensional accuracy and shape accuracy, precision of IT7 ~ IT6 level, roundness and cylindrical hole error can be controlled within the range, but can not improve the position of honing precision machined hole.
2) honing obtain a higher surface quality, surface roughness Ra of 0.2 ~ 0.25μm, deterioration of the surface of the metal defect depth minimal 2.5 ~ 25μm.
3) Compared to grinding speed, the peripheral speed of the honing head is not high (vc = 16 ~ 60m / min), but due to the contact strip of sand with the workpiece area, the reciprocating relatively high speed (va = 8 ~ 20m / min), so there is still honing higher productivity.

Honing in a large number of mass production is widely used in the manufacture of engine cylinder bores and various hydraulic devices precision hole or pore size range is generally greater, and processing aspect ratio greater than 10 deep. Honing but does not apply to non-ferrous metal processing of plastic large hole on the workpiece, the hole can not be processed with keyway, spline hole and the like.


Fifth, broaching

1. broaching and broach

Pull finishing hole is a method of high productivity, it is with a special broach pull the bed made. Horizontal and vertical broaching broaching broaching points are two, with horizontal broaching the most common.

Broach only for low-speed linear motion (main motion) when broaching. While the number of teeth Broach work should generally be less than three, otherwise broach work is not smooth, easy to produce cyclic ripples in the surface. In order to avoid excessive broaching force of the broach breaking, broaches work, knife work while the number of teeth should not exceed 6 to 8.

Broaching broaching There are three different ways, as described below:

1) hierarchical broaching broaching this way is characterized broach the workpiece allowance sequentially removed layer by layer. In order to facilitate breaker, teeth grinding have staggered on the sub-flutes. By way of broaching hierarchical design called common broach broach.

2) sub-block broaching broaching this way each layer is characterized by a metal working surface is formed by a set of substantially the same size, but teeth interdigitated teeth (usually made each consisting of 2-3 teeth) resection. Each tooth is only part of the layer of metal is cut. By way of broaching block design broach called round-cut broaches.

3) Integrated type broaching this way the advantages of centralized and hierarchical sub-block broaching, gear cutting rough part of the block-type broaching, gear cutting part layered fine broaching. This will not only shorten the length of the broach, increase productivity, but also to obtain a better surface quality. Comprehensive design by way of broaching the broach called integrated type broaches.

2. Pull hole process features and applications

1) Broach multi-point tool, a broaching stroke in order to complete the hole can be rough, finishing and finishing work, high production efficiency.

2) broaching accuracy depends on the accuracy of broaches, under normal conditions, broaching accuracy up to IT9 ~ IT7, surface roughness Ra of up to 6.3 ~ 1.6 μm.

3) When broaching the workpiece to be machined hole positioning itself (broaches the preamble portion of the workpiece is positioned element), broaching difficult to guarantee mutual position accuracy of holes and other surface; for those who have the inner and outer peripheral surface of the rotary concentricity requirements processed body parts are often the first to pull the hole, then positioning reference hole machining other surfaces.
4) Broach be processed not only circular, but also the hole forming process, the spline hole.

5) is sized broach tool, shape complex, expensive, not suitable for processing large holes.

Broaching commonly used in a large number of mass production and processing pore diameter Ф10 ~ 80mm, through-hole aperture hole depth does not exceed five times the small part.