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Definition of scientific terms
Chinese name:TapEnglish name:tapDefinition：Standard tools for machining cylindrical and conical internal threads.
A tool for machining internal threads, with grooves along the axis. It's called a screw attack. The tap is divided into straight slot tap, spiral groove tap and tap tap according to its shape. Straight groove taps are easy to process with low precision and large output. It is generally used for thread processing of ordinary lathe, drilling machine and tapping machine, and the cutting speed is slow. Spiral groove taps are usually used in drilling holes of NC machining center. The processing speed is fast, the precision is high, the chip removal is better and the neutral is good. There are grooves in the front of the screw tap, which is used for the machining of the through hole.
Taps are mostly coated taps, and the service life and cutting performance of uncoated taps are greatly improved. The cutting load distribution of taps with unequal diameter design is reasonable, the machining quality is high, but the manufacturing cost is also high. Trapezoidal thread taps are usually designed with unequal diameters.
Machine and hand taps are standard taps for cutting ordinary threads. In China, it is customary to call the high speed steel molar tooth as the machine tap, and the screw (or incisor) tap of carbon tool steel or alloy tool steel is called hand tap
The working principle is basically the same. Usually, the tap is made up of the working part and the shank. The working part is divided into the cutting part and the calibration part. The former has a cutting cone, which is responsible for the cutting work, and the latter is used to calibrate the size and shape of the thread.
For processing or other parts of the ordinary nut internal thread with (i.e. tapping). Machine taps usually refers to high speed steel geared tap on the machine tool, suitable for tapping; hand taps refers to carbon tool steel or alloy tool steel rolling (or incisor) tap, suitable for manual tapping
The tap is a tool for machining various middle and small sizes of internal thread. It is simple in structure and easy to use. It can be operated by hand or on machine tools. It is widely used in production.
The thread of the small size of the fibers, is almost the only tool. The types of fibers: hand taps, machine taps, nut taps, extrusion Taps etc..
To process tapping is difficult, because the tap is almost buried in cutting the workpiece, the processing load of each tooth is larger than the other tool, and contact with the workpiece surface along the screw tap is very large, cutting thread when it must accommodate and remove the chip, therefore, can be said that the tap is working in very harsh conditions. In order to make the tapping smoothly, all possible problems should be considered in advance. Such as the material properties of the workpiece, the choice of what tools and machine tools, the choice of high cutting speed, feed and so on.
Machinability of workpiece material is the key to tapping difficulty. Now taps manufacturers are mainly concerned about the development
Taps for machining special materials. In view of the performance of these materials, the geometry of the cutting part of the tap, especially the front angle and the concave volume (HOOK) - the front concave degree, is changed. The highest processing speed is sometimes limited by machine performance. For smaller spindles, the spindle speed to achieve an ideal speed [rpm= (sfmx3.8) / tap diameter] may exceed the maximum speed of the spindle. On the other hand, the high speed cutting with larger tap will produce greater torque, which may be greater than the power provided by the machine tool. With the 700psi internal cooling tool, the cutting speed may reach 250sfm. In the machine tool without internal cooling, the cutting speed can only reach 150sfm. Silk is different from most metal cutting tools, because it has very large contact area with the workpiece hole wall, so cooling is very important. If the high speed steel cone is overheated, then the wire push will break and burn, and the NORIS company's high performance wire rod has the characteristics of big back angle and reverse cone."
The geometry of the tap and the special coating surface (such as TiN, TiCN, CrN or TiAlN) can greatly improve the life of the tap. These heat resistant, smooth coatings reduce the cutting force and allow tapping at higher cutting speeds. In fact, the development of the new high performance taps greatly promotes the spindle speed and power of the machine tool.
As hard alloy tools gradually replace high speed steel tools in turning, hard alloy taps begin to be more used in thread hole machining. Compared with high speed steel, cemented carbide has high hardness and brittleness. Even so, cemented carbide taps are very effective in processing cast iron and aluminum alloy materials, and the main form of breakage is mechanical wear.
Because the automobile industry processes a large number of cast iron and aluminum alloy parts, the hard alloy tap is used to obtain the long life of the tool. Tungsten carbide taps have longer life span than high speed steel cones in machining these materials. In the automotive industry, the reduction of the tool time is an important factor, while the long life of the hard alloy wire will minimize the tool changing time. The small screw angle cemented carbide tap with surface coating is applied to the aluminum alloy workpiece with silicon content of 8%-12%, and the effect is very good. With fine particles (Submicron-grain) tap hard alloy production, can increase the toughness of the tool without reducing the hardness, the effect on cutting of hardened steel, plastic and hard machining of nickel based alloy is very good. DL15Ni series of nickel alloy special wire pushed by NORIS company, under certain conditions, can continuously tap 200 screw holes on the nickel chromium iron alloy Inconel718, and must be regrinding before reaching.
Taps are usually divided into single or group. Small and medium sized through hole can be attacked by single tap at one time. When machining blind hole or large size screw hole, the group tap is usually used, that is, the processing of one screw hole is completed by more than 2 taps. Group taps have equal diameter and unequal diameter
Two designs. The taps of equal diameter design only have different length of the cutting cone; the thread sizes of the taps designed with unequal diameters are different, and only the last one has a complete tooth shape. The cutting load distribution of taps with unequal diameter design is reasonable, the machining quality is high, but the manufacturing cost is also high. Trapezoidal thread taps are usually designed with unequal diameters.
In order to improve the cutting efficiency of tap, improve the chip and chip removal, reduce tooth breaking and breaking, modern taps have a variety of new structures. (1) screw tip tap: the cutting part is inclined to grind and form a negative edge angle (see cutting tool). When cutting, the chip is discharged forward, which is suitable for machining through hole.
The spiral groove taps: the chip groove is spiral, in processing the blind hole right thread, the tap must make the right spiral chip groove, so that the chip is discharged forward, not scratch the thread.
(3) no slot extrusion tap: the plastic deformation of the metal formed by extruding the hole wall is mainly used for processing aluminum alloy, copper and other plastic materials, and can also process low carbon steel and stainless steel. The taper of the front end of the tap is conical thread. In order to reduce friction and reduce extrusion force, the tap section is made into polygon. The extruding tap has high strength, and is especially suitable for machining small size screw holes with diameters less than 6 millimeters.
The screw tap along the cutter tooth spiral direction and remove a tooth, thus increasing the chip thickness, in favor of chip breaking and chip, used for processing stainless steel workpiece.
Chip tap: the chip is discharged from the inner hole of the tap, and is used for machining large size screw holes.
The automatic contraction tap: tapping tap tooth after automatic inward contraction for quick exit.
The tap is a knife tooth distribution on the spiral line broach, commonly used in the processing of trapezoid and square thread.
The tap: mainly used for processing hard alloy cast iron and nonferrous metals, high cutting efficiency and tool life.
(1) when tapping, insert the nose to tap the center line and the center line of drilling.
(2) rotate the two hands evenly and add a little pressure to the tap to feed. No pressure is needed after the feed. (3) each turn tap is rotated about 45 degrees at once to cut the chip so as not to block.
(4) if the tap is difficult to rotate, the rotation force can not be increased, otherwise the tap will break.
Thread is the most common method of mechanical parts connection, and tap is the most commonly used tool for processing internal thread. The correct selection of tap to process internal thread can ensure the quality of thread connection and improve the service life of tap.
Domestic machine taps are marked with the middle diameter tolerance band code: H1, H2 and H3, respectively, indicating different tolerances, but the tolerance values are equal. The tolerance band code of hand tap is H4, and the tolerance value, pitch angle and angle error are larger than that of machine tap. The material, heat treatment and production process are not as good as that of machine tap. H4 can not be marked according to regulations. The tolerance level of the internal thread that can be machined by the middle diameter tolerance zone of tap is as follows:
Tap tolerance zone code applicable to internal thread tolerance grade
Some enterprises use imported taps, German manufacturers are often marked as ISO14H, ISO26H, ISO36G (international standard ISO1-3 and national standard H1-3 is equivalent), so the taps tolerance zone code and machinable internal thread tolerance zone are marked.
The common thread has three types: metric, imperial, unified system (also called us). Metric is a thread with a tooth angle of 60 degrees in millimeters. For example, M8X1-6H stands for metric fine tooth threads with a diameter of 8 mm, thread pitch 1 mm, 6H internal thread tolerance zone.
The inch is in inches, and the tooth angle is 55 degrees. For example, BSW1/4-20 stands for 1/4 inches in diameter and 20 teeth per inch in coarse teeth. This thread is rarely used now. Another uniform is in inches, tooth angle 60 degrees thread. Diameter less than 1/4 inch,
Commonly used numbered representations, from 0 to 12, represent diameters of 0.06 inches to 1/4 inches. The United States is still the main use of unified thread.
We often use is: straight fluted tap, spiral tap, screw tap, squeeze tap, the performance of each one has his good points.
Straight slot taps are the most versatile, through holes or holes, non-ferrous metals or ferrous metals can be processed, the cheapest price. But the pertinence is poor, anything can be done, nothing is the best. Spiral groove taps are more suitable for machining non hole threads, and chip is discharged backwards during machining. Because of the screw angle, the actual rake angle of the tap increases with the increase of the helix angle.
Experience tells us: the processing of ferrous metal, spiral angle election of a small point, generally at about 30 degrees, to ensure the strength of spiral teeth. Processing non-ferrous metals, spiral angle election of a larger point, can be about 45 degrees, cutting a bit sharp. When the threaded tap is used to process the thread, the chip is discharged forward. Its core size design is relatively large, the strength is good, can withstand larger cutting force. Machining of non-ferrous metals, stainless steel, ferrous metal effect is very good, through the hole thread should be preferred screw tip tap. Extrusion tap is more suitable for processing non-ferrous metals, and the working principle of the above-mentioned cutting tap is different, it is to squeeze metal, make it deformation, forming internal thread. Internal thread of metal fiber extrusion is continuous, tensile, shear strength high, the processing of the surface roughness is also good, but require a higher extrusion tap hole: too large, base metal less, causing the thread is too large, the strength is not enough. Too small, closed squeeze metal nowhere to go, resulting in broken tap. Calculation formula: diameter = bottom thread diameter -0.5 pitch.
Tap according to its shape is divided into: straight slot spiral fluted tap, tap, tap, screw tap swarf, extrusion tap, the performance of each one has his good points.
It is the most versatile, through holes or through holes, non-ferrous metals or ferrous metals can be processed, the cheapest price. But the pertinence is poor, anything can be done, nothing is the best. The cutting cone can have 2, 4 and 6 teeth, and the short cone is not suitable
Holes and long cones are used for through holes. As long as the bottom hole deep enough, you should try to choose the cutting cone is longer, so to share the load of cutting tooth number, the service life is long.
It is more suitable for machining non hole thread, and the chip is discharged backwards when machining. Because of the screw angle, the actual rake angle of the tap increases with the increase of the helix angle. Experience tells us: the processing of ferrous metal, spiral angle election of a small point, generally at about 30 degrees, to ensure the strength of spiral teeth. Processing non-ferrous metals, spiral angle election of a larger point, can be about 45 degrees, cutting a bit sharp.
Chip tap is a patented product of NORIS company in germany. Its characteristic is that a big enough chip groove is opened at the head, and the special setting is adopted
In order to achieve higher machining quality. Especially in the large thread processing advantages. Widely used in wind power, steam turbine, shipbuilding, mining, oil and other industries.
China began to introduce content taps M56~M90 from West Germany NORIS company during "75" period. It has good application effect in large state-owned enterprises such as Harbin steam turbine factory, Shanghai shipyard, Dalian shipyard, Shaanxi diesel engine factory and so on, and achieved good economic benefits.
When the thread is machined, the chip is discharged forward. Its core size design is relatively large, the strength is good, can withstand
Large cutting force. Machining of non-ferrous metals, stainless steel, ferrous metal effect is very good, through the hole thread should be preferred screw tip tap.
It is more suitable for machining non-ferrous metal. It is different from the working principle of the cutting tap, it is to squeeze the metal, make it deformation, forming internal thread. Internal thread of metal fiber extrusion is continuous, tensile, shear strength high, the processing of the surface roughness is also good, but require a higher extrusion tap hole: too large, base metal less, causing the thread is too large, the strength is not enough. Too small, closed squeeze metal nowhere to go, resulting in broken tap. Calculation formula: diameter = bottom thread diameter -0.5 pitch.
According to the method of use, it is often divided into hand tap, machine tap, nut tap (used in nut processing machine)
The bed cut thread), die tap (used for cutting and correcting die thread), pipe thread tap and taper thread tap.
It is a standard tap for cutting ordinary thread. In China, it is customary to call the high speed steel molar tooth as the machine tap, and the screw (or incisor) tap of carbon tool steel or alloy tool steel is called hand tap, in fact, the structure and working principle of the two are basically the same. Usually, the tap is made up of the working part and the shank. The working part is divided into the cutting part and the calibration part. The former has a cutting cone, which is responsible for the cutting work, and the latter is used to calibrate the size and shape of the thread.
1, tapping the end of the hole should be chamfered; tap with the workpiece hole coaxial; tapping start should be applied to the axial pressure, so that tap into the cut, cut into a few laps after the axial force no longer need to be applied.
2, when the tap calibration part into the screw hole, each positive half turns to a circle to return 1/4, 1/2 ring, the chip broken down again after school; take the through hole, often exit tap chip.
In 3, the steel workpiece tapping on to cutting fluid tapping in cast iron workpiece, can add a little kerosene; with a taper, and then two attack and three attack, must be screwed in the screw tap.
4, the end of the workpiece should be chamfered, the end of the tooth should be perpendicular to the axis of the workpiece; when the thread starts, the axial pressure should be applied; the rotation pressure should be larger; when the screw thread is cut on the workpiece, no pressure should be added.
5, in order to make the chip broken, timely discharge, should often reverse the tooth.
6, the work should be firmly fixed in the clamp, a clamping device; when the tap is broken, a hand to touch off don't clamp, chisel or punching out, broken wires must wear protective glasses.
Tap the threaded hole machining, hole diameter is small, chip is not good due to clogging of the blind hole; thread when the drilling depth is not enough; tapping taper screw speed is too high too fast; the diameter of tap and the tap tapping tapping taper thread with different axis; tap sharpening parameters is not suitable workpiece hardness; instability; tap used for a long time, excessive wear.
The diameter of the bottom thread correctly; grinding edge inclination or selection of spiral fluted taps; drilling bottom hole depth to meet the prescribed standards; appropriate to reduce the cutting speed, according to the selection criteria; correction of taper thread tap and bottom tapping, ensure the coaxiality requirements, and selection of floating cone thread tapping chuck increases; the corner tap, shorten the length of the cutting cone; ensure the workpiece hardness to meet the requirements, the insurance holder; found the tap wear should be replaced.
The tap angle is too large; the cutting thickness of each tap is too large; the quenching hardness of tap is too high; the tap is worn seriously.
Properly reduce the rake angle of the tap, increase the length of the cutting cone properly, reduce the hardness and replace the tap in time.
When tapping thread, the speed is too high; the selection of grinding parameters is not suitable; the improper choice of cutting fluid; inadequate use; the material hardness of workpiece is too high; when the tap is grinding, the phenomenon of burning occurs.
The cutting speed should be reduced; the front angle of the tap should be reduced; the length of the cutting cone should be lengthened; the lubricating cutting fluid should be selected; the proper heat treatment for the workpiece to be processed; and the correct grinding tap.
Tap in size precision improper selection of cutting fluid; unreasonable selection; tapping taper screw speed is too high; tap tap tapping and workpiece coaxiality deviation; grinding parameters are not appropriate tap edge grinding burrs; tap; tap cutting cone length too short.
Select the appropriate levels of precision tap diameter; and reducing the cutting speed selection of cutting fluid suitable; tapping taper thread taps and correcting the tap thread bottom hole coaxiality; floating chuck; reduce the rake angle and cutting cone angle; eliminate burr grinding taps generated, and to appropriately increase the length of the cutting cone.
The selection of the middle diameter accuracy of tap is improper; the grinding parameters of tap are not suitable; the tap is worn; the choice of cutting fluid is not suitable.
The middle diameter of tap suitable for accuracy grade should be selected; the front angle and taper of tap should be increased; the worn tap should be replaced; and the cutting fluid with good lubrication should be selected.
The grinding parameters of tap are not suitable; the material hardness of workpiece is too low; the quality of tap grinding is poor; the choice of cutting fluid is improper; the tapping speed of tapping cone thread is too high; the tap wear is large.
Properly increase the rake angle of the tap, reduce the cutting taper; heat treatment, appropriately improve the hardness of the workpiece; ensure the lower surface roughness of the tap rake surface; select good lubrication cutting fluid; properly reduce the cutting speed; replace worn taps.
(1) the workpiece orifice to the threaded hole chamfering, screw through holes at both ends chamfering.
(2) the position of the workpiece clamp should be correct, and the center line of the thread hole should be placed in the horizontal or vertical position, so that it is easy to judge whether the thread of the tap is perpendicular to the plane of the workpiece.
(3) in tapping at the beginning, we should try to put it on the tap, then tap the pressure and rotate the holder, when starting 1-2 circle, carefully check and correction of tap position. The tap position should be correct when the thread is cut into 3-4 circles. Later, only by rotating the holder, and add pressure to the tap should not, otherwise the thread form will be damaged.
(4) when tapping, each turn holder 1/2-1 circle, it should be back about 1/2 ring, the chip broken off easily discharged, and can reduce the cutting edge for crumbs to tap jam phenomenon.
(5) when tapping the hole, always tap out the tap and eliminate the chip in the hole.
(6) when tapping the screw holes of the plastic material, the lubricating coolant should be added. For steel materials, oil or molybdenum disulfide, which requires higher oil or larger concentration of emulsion, is available. For stainless steel, 30 oil or vulcanized oil can be used.
(7) for use after a tap tapping process, must first with the hand screw has been tapping, to no precession, and then use the tapping head turn. At the end of the cone end exit, but also to avoid the fast rotating holder, the best hand spin out, to ensure good quality of the thread is not affected.
(8) when machine attack, tap and screw hole to keep coaxial.
(9) when the machine attack, the calibration part of the tap can not all head, otherwise in the anti car exit tap will produce messy teeth.
Oxidation treatment is a kind of surface treatment method to make high-speed steel wire into 500-550 degrees of water vapor and make its surface form Fe3O4 film. Oxidation treatment is also called high pressure steam treatment.
Iron oxide, FeO, Fe2O3, Fe3O4 three FeO, which can only be generated at 570 DEG C, so it is in the surface layer of high speed steel tap does not exist, there is Fe3O4 in the surface layer (iron) and tap Fe2O3 (Hong Tie) two, the latter cutting of tap no benefit, after high quality surface treatment, processing layer is Fe3O4 film taps, installed surface appearance, with blue black, the top layer is 1-3um.
1. oxidation characteristics
Oxidation treatment can improve the performance of taps because the surface layer is porous, and the adsorption of coolant is good, can play a role in reducing friction. Meanwhile, the bond between the tap and the cutting material can be prevented. In addition, the grinding stress remaining on the surface of the tap is removed.
However, it is important to note that the film formed by oxidation treatment can not improve the hardness of the surface layer of the tap, i.e., the film itself has no wear resistance.
2. scope of application
Taps after oxidation treatment of stainless steel, cast steel, carbon steel, nickel steel, chrome steel, easy to produce the cut material bonding effect is very good, almost can be applicable to the processing of all steel parts.
But it should be noted that the oxidation treatment of aluminum alloy, die casting aluminum alloy, brass and other non-metallic materials have not particularly good effect, and may even reduce the cutting performance of taps.
Oxidation treatment is widely used in various types of taps (refer to NORIS taps).
3. cutting performance
When the stainless steel (austenitic system) workpiece is easy to be bonded with the edge angle tap, the life of taps can be increased by more than 10 times by oxidation treatment. This is also evident from the experimental example of NORIS universal tap for carbon steel. Oxidation treatment significantly improves the tap life.