Hole machining drilling countersinking reaming
Hole machining drilling countersinking reaming
Drilling holes during assembly is necessary if:
the required accuracy is achieved most easily by machining two or more assembled parts; the place of drilling is hard to reach for machining on the machine, and a small diameter hole can be drilled with a power tool;
the hole was not provided during the manufacture of the part.
When drilling holes with a diameter of up to 10.12 mm, portable drilling devices with different designs of drills or small machines on columns are used. For drilling larger holes, machines are used on the foundation Drilling of holes in places where the use of machines is impossible is carried out with pneumatic and electric machines of different capacities.
The modes of the drilling process, the accuracy of diametrical dimensions and center distances are well known.
Countersinking. processing of pre-drilled, stamped, cast holes in order to give them a more regular geometric shape (elimination of deviations from roundness and other defects), to achieve higher accuracy (9.11 grade) and to reduce the surface roughness to Ra 1.25. 2.5 microns. This processing can be either final or intermediate (semi-final) before deployment. When processing precise holes with a diameter of less than 12 mm, instead of countersinking, immediately reaming is used.
The nature of the work of the countersink is similar to the work of the drill when reaming the hole. By design
and the design of the cutting edges, the countersink differs from the drill and has three to four teeth, which ensure the correct and more stable position of the countersink relative to the axis of the hole being machined. Countersinks are solid and mounted (2.40). To save high-speed steel, they are also made with plug-in knives or with soldered carbide plates.
Countersink and e. processing by countersinks of cylindrical or conical recesses and chamfers for the heads of bolts, screws, rivets. Unlike countersinks, countersinks have cutting teeth at the end and guide pins, with which they are inserted into the drilled hole. This ensures the alignment of the axis of the hole and the recess formed by the countersink for the screw head. Mounting countersinks on drilling machines is no different from mounting drills.
Reaming. Finish holes for high precision
dimensions and surface roughness within Ra 1.25. 0.16 μm. Reaming of holes is performed on drilling and other metal-working machines, as well as manually during locksmith and fitter-assembly processing. Manual reamers are available with straight and helical teeth, plug-in and adjustable. They have a square end on the shank for
rotating them with a crank. The pitch of the teeth (angular pitch) of the reamers is uneven, which reduces the possibility of the formation of a polyhedral hole. Reamers used on machines are called machine reamers and differ from manual reamers in a shorter working part and the presence of a tapered shank. Machine reamers are fixed in floating (swinging) mandrels or chucks, which allows them to self-align along the axis of the drilled hole, and also eliminates hole punching.
To process tapered holes, most often Morse tapers, tapered hand reamers are used in sets of two and three pieces (2.41.0). The first development is rough (rough), the second is intermediate and the third is finishing (final).
Deployment allowance should be no more than 0.05. 0.1 mm per side. A larger allowance can lead to a quick dullness of the intake part of the reamer, an increase in the roughness of the hole surface and a decrease in machining accuracy.
Before starting the deployment, it is necessary to: select the required flat pattern by checking its marking; make sure there are no nicks and chipped places on the cutting edges; fix the workpiece in a vice or install it on a workbench (plate) in a position convenient for work; lubricate the intake part of the reamer with mineral oil and insert it into the hole without skewing; check the position of the reamer relative to the axis of the hole with a square; put the knob on the square of the shank. Then, lightly pressing the reamer with your right hand, slowly rotate the crank clockwise with your left hand. The collar must be rotated slowly, smoothly and without jerks. Reverse rotation of the reamer is unacceptable, as it can cause scoring on the surface of the hole or breakage of the reamer cutting edges. The reamer must be periodically removed from the hole to clean it of chips and lubricate it. Deployment is finished when the 3D working part of the reamer comes out of the hole. For deep holes located in hard-to-reach places, special extensions are used that fit over the square of the reamer shank,
The final (clean) deployment is performed in the same sequence.
On drilling machines, it is better to deploy the deployment immediately after drilling and countersinking with one installation of the workpiece in a vice or fixture. The reamer is fixed using a chuck or adapter sleeves in the cone of the machine spindle. In some cases, to ensure a more accurate coincidence of the axes of the sweep and the hole, the machine reamers are fixed in floating (swinging) chucks. The cutting speed (spindle speed) during reaming should be 2.3 times less than when drilling with a drill of the same diameter. Deployment is carried out with a mechanical feed, which depends on the diameter of the reamer, the material of the workpiece and is taken within 0.5. 2.0 rpm As a cutting fluid for steel and bronze billets, a solution of Zmulsol, mineral oil; for cast iron and aluminum alloys. kerosene, turpentine; for ductile iron and brass. emulsol solution.
The surface quality of the reamed hole is checked after thorough wiping by external inspection to light to detect scoring, faceting, and traces of crushing. The accuracy of the hole is determined depending on? its size and the required quality of accuracy with plug gauges, indicator bore gauges, and holes with a diameter of more than 50 mm. with bore micrometers.
To mechanize the deployment process, use electric or pneumatic drilling machines with additional gearboxes that reduce the spindle speed to 30.50 rpm.
Locksmith assembly work is carried out using various assembly tools (wrenches, screwdrivers, hammers) and devices.
Locksmith work completes metal machining. Assembly and adjustment of mechanisms and machines are also related to locksmith work.
§ 1. Types of plumbing work. Modern locksmith work has become more versatile and covers various types of production.
Assembly and assembly work consists of working operations that are performed in a specific sequence.
Locksmith and tool work.
When performing assembly and locksmith work, for assembly and disassembly, use double-sided wrenches with an open jaw, one-sided with an open jaw.
Study guides. Metal processing. Plumbing. EAT. Muravyov. Introduction.
§ 27. Detachable connections. § 28. One-piece connections. Section 29. Assembly of parts.
Locksmith and tool works. Section: Construction.
§ 1. Types of plumbing work. § 2. Requirements of NOT for plumbing and tool work.
Installation and assembly work on all types of sanitary devices is performed by complex teams, and for certain types
Locksmith and tool work.
Pneumatic rotary drilling machines of small sizes with an angle attachment are widely used when performing plumbing and tooling and assembly work.
Wood and metal processing
Reaming is the process of finishing the holes, which ensures the accuracy of the 7th-9th grade and the surface roughness of the 7th-8th grade. Deployment Tool. Sweeps.
The reaming of the holes is carried out on drilling and turning machines or manually. Reamers used for manual reaming are called manual, and for machine reaming. machine reamers. Machine reamers have a shorter working section.
According to the shape of the hole being machined, the reamers are subdivided into cylindrical and conical. Manual and machine reamers consist of three main parts: working, neck and shank.
The working part of the reamer, on which there are teeth located around the circumference, is in turn divided into a cutting, or intake, part, a calibrating cylindrical part and an inverse taper.
The cutting, or intake, part at the end has a guide cone (bevel at an angle of 45 °), the purpose of which is to remove the reaming allowance and protect the top of the cutting edges from nicks during reaming.
The cutting edges of the intake part form an angle at the top of 2F with the sweep axis (for manual sweeps 0.5. 1.5 °, and for machine sweeps 3-5 °).
The calibrating part is designed to calibrate the hole and the direction of the reamer during operation. Each tooth of the gauging part along the working part of the reamer ends with a groove, due to which the cutting edges are formed; in addition, the grooves serve to evacuate chips.
The back taper is on the gauge part closer to the shank. It serves to reduce the friction of the reamer on the hole surface and maintain the quality of the machined surface when the reamer exits the hole.
For manual reamers, the value of the reverse cone is from 0.05 to 0.10 mm, and for machine reamers. from 0.04 to 0.3 mm.
The reamer neck is located behind the reverse taper and is intended for the exit of the cutter when milling (cutting) on the reamers of the teeth, as well as the grinding wheel when sharpening.
The hand reamer shank has a square for the driver. The shank of machine reamers with a diameter of 10-12 mm is cylindrical, more cope reamers. conical.
Center holes are used to install the reamer during its manufacture, as well as when sharpening and regrinding teeth.
The cutting elements of the reamer are the teeth.
The teeth of the sweep are determined by the back angle (6-15 °; large values are taken for sweeps of large diameters), the angle of sharpening (3, the front angle y (for rough sweeps from 0 to 10 °. For fine sweeps. 0 °).
The angles of sharpening p and cutting 5 are determined depending on the angles a and Y.
Reamers are made with a uniform and uneven distribution of teeth around the circumference. In manual deployment, teeth with an uneven distribution of teeth around the circumference are used, for example, in a reamer with eight teeth, the angles between the teeth will be: 42, 44, 46 and 48 °. Such a distribution ensures that a cleaner surface is obtained in the hole, and most importantly, it limits the possibility of the formation of the so-called faceting, that is, the formation of holes is not cylindrical, but multifaceted.
If the sweep pitch were uniform, then at each turn of the sweep knob, the teeth would stop in the same place, which would inevitably lead to a waviness (faceted) surface.
Machine reamers are made with a uniform distribution of teeth around the circumference. The number of teeth of reamers is even: 6, 8, 10, etc. The more teeth, the higher the processing quality.
Manual and machine reamers are performed with straight (spur) and helical (spiral) grooves. According to the directions of the helical grooves, they are divided into right and left.
Introduction to Reaming
When working with a reamer with a spiral tooth, the surface is cleaner than when working with a straight tooth. However, the manufacture and especially sharpening of reamers with a spiral tooth is very difficult, and therefore such reamers are used only when reaming holes in which there are grooves or grooves.
Both conical and cylindrical reamers are made in sets of two or three pieces. In a set of two pieces, one is preliminary and the other is final. In a set of three pieces, the first reamer is rough or rough, the second is semi-finishing and the third is finishing, which gives the hole the final dimensions and the required roughness.
Conical reamers work in more severe conditions than cylindrical reamers, therefore, for conical reamers on straight teeth, transverse slots are made to remove chips not with the entire length of the tooth, which significantly reduces cutting forces. over, since the rough sweep removes a large allowance, it is made stepwise, in the form of individual teeth, which, during operation, crush the chips into small pieces. On the intermediate reamer, which removes significantly less chips, the slots are made smaller and the other profile. A fine reamer does not have any chip grooves.
Manual cylindrical reamers are used for reaming holes with a diameter of 3 to 60 mm. According to the degree of accuracy, they are divided by numbers: 1,2 and 3.
Machine reamers with a cylindrical shank are made of three types: I, II and III. Reamers are used to process holes of the 6th-8th grade. They are manufactured with a diameter of 3. 50 mm. The reamers are fixed in self-centering chucks of machine tools.
Machine reamers with a tapered shank of type II are made with a diameter of 10 to 18 mm and a shorter working part. This reamer is fixed directly in the spindle of the machine.
Machine shell reamers of type III are made with a diameter of 25. 50 mm. These reamers process the hole of the 5th-6th qualifications.
Machine reamers with a square head are made with a diameter of 10. 32 mm, are designed to process holes in 6-7 grades, are fixed in cartridges that allow swinging and self-centering of reamers in the holes.
Reamers with plug-in knives of type I (mounted) have the same purpose as the previous ones, and they are made with a diameter of 25-100 mm.
Machine reamers, equipped with T15K6 hard alloy plates, are used to process holes of large diameters with high speed and high accuracy.
In addition to the considered designs of reamers, other reamers are widely used that increase the accuracy and quality of hole processing.
Sliding (adjustable) reamers are used when reaming holes with a diameter of 24 to 80 mm. They allow an increase in diameter of 0.25. 0.5 mm.
Adjustable sweeps are the most common. They consist of a body that lasts a long time and are made of relatively inexpensive structural steels and simple shaped knives. Knives are made from thin plates, they consume a small amount of expensive metal. They can be rearranged or extended to a larger diameter, adjusting or sharpening to the desired size. When the knives are grinded and no longer provide a secure attachment, they are replaced with new ones.
To deploy through holes, expanding reamers are widely used (Fig. 246.6), in which the knives are fastened either with screws, or in precisely fitted grooves, they are pressed to the bottom of the groove with tapered grooves of end nuts, or with screws that expand the body.
When working with a reamer on a machine, there are often cases when, with a rigidly fixed reamer, its axis does not coincide with the axis of the hole being machined, and therefore the reamed hole turns out to be of an irregular shape. This happens with a faulty machine: the spindle rotation axis does not coincide with the hole axis (spindle runout).
To improve the quality of processing and to avoid rejects when reaming the hole, swing mandrels are used.
The swinging mandrel is fixed in the machine spindle with a tapered shank. In the housing bore, the swinging part of the mandrel is fastened with a pin with a gap, which rests with a ball against the thrust bearing. Thanks to such a device, the swinging mandrel with a reamer can easily take a position coinciding with the axis of the reamer hole.
To obtain high accuracy of the hole, floating reamers are used, which are plates inserted into precisely machined grooves of a cylindrical mandrel. The outer edges of the plate are sharpened in the same way as the reamer tooth. To ensure regulation, the layers are made composite. When working with floating reamers, exact alignment of the hole to be machined and the machine spindle is not needed and, in addition, an accurate hole is obtained even when the spindle beats, since the plate with its ribbons is centered along the walls of the hole, moving in the slot of the mandrel in the transverse direction. The use of a rational design of reamers not only ensures high quality of work, but also significantly increases labor productivity.
In some engineering plants, when reaming the tapered holes, a restricting retaining ring is placed on the tapered part of the reamer, which eliminates the cost. time to measure.
To reduce the load on the sweep during operation, the length of its intake part is doubled. This eliminates the need for a second sweep and improves productivity and processing accuracy.
The combined tool for simultaneous drilling and countersinking of a hole is widely used.
Drill-countersink, drill-countersink, drill-reamer, countersink-reamer allow you to combine two operations and get a hole of a given shape, quality and roughness.
Characteristics of types of blade processing of holes
On drilling and boring machines, different types of blade processing are used to make holes (Fig. 1; Fig. 2): drilling, reaming, countersinking, reaming, countersinking, counterbore, chamfering, boring, threading, etc.
Drilling. They are used to obtain through and blind holes in a solid workpiece material with a twist drill. In this case, the diameter of the holes to be machined usually does not exceed 15 mm. The shaping of surfaces during drilling (Fig. 1, a) is carried out by two movements, which are communicated to the tool: rotational and translational. The rotation of the tool is the main cutting movement Dr and kinematically reproduces the guide circle 2. The continuous rectilinear movement of the tool in the vertical plane is the feed motion BSD and reproduces the generatrix 1.
For the speed of the main cutting movement during drilling, the peripheral speed of the point of the cutting edge of the tool farthest from the axis of the drill is taken:
v = πdn /(60.1000) m / s,
where d is the diameter of the twist drill, mm; n. frequency of rotation of the cutting tool, min. 1.
Feed SB, mm / rev, when drilling is called the movement of the drill in the vertical plane in one revolution.
When drilling a hole in a solid material, the depth of cut t, mm, is equal to half the diameter of the drill. It is measured in a plane perpendicular to the direction of feed: t = d / 2.
The drilled holes have a roughness parameter Ra = 5.16 µm and an accuracy corresponding to 12.14 grade. Large cutting force, crushing (and not cutting) during drilling due to the transverse cutting edge of the drill, as well as not the rigidity of the drill, its cantilever clamping lead to the fact that even small inaccuracies in sharpening, deviations from the symmetry of the cutting part design can cause axis drift drills (with a drilling depth L ≥ 5d) and “breakout” of the hole (increase in its diameter compared to the diameter of the drill). For twist drills, the “breakdown” is 1% of the drill diameter. Therefore, holes obtained by drilling, as a rule, have deviations in shape in longitudinal and cross sections, as well as deviations in the location of the hole axis from the reference surfaces of the product. Drilled holes are usually used for bolting or for subsequent threading.
Reaming. A type of processing designed to increase the diameter of a previously drilled hole (Fig. 2 a), with a twist drill of a larger diameter (more than 15 mm). The parameters of roughness and accuracy are the same as for drilling. Depth of cut for reaming:
where D is the tool diameter, mm; d. diameter of the hole to be machined, mm.
Countersinking. They are used for processing blind and through holes, previously prepared by drilling or obtained in workpieces by casting, forging or stamping (Fig. 2 b). Distinguish between rough and finish countersinking. Processing is performed with a multi-edge tool. a countersink. Compared to a drill, a countersink has a greater number of cutting blades and greater rigidity. The shallower depth and lower cutting force allows you to get a hole more accurate in geometric shape and dimensions (8.12 grade of accuracy) and the roughness of the machined surface Ra = 3.2. 10 microns.
Deployment. They are used for finishing cylindrical and tapered holes (Fig. 2 c), usually after countersinking or boring. There are the following types of unfolding: rough (normal), fine (fine) and fine. When deploying, an accuracy corresponding to 6.9 grade is achieved, and a roughness Ra = 0.32. 1.25 microns. Reaming is carried out with reamers, which are a multi-edge tool with an even number of cutting blades. Standard one-piece machine reamers, depending on their diameter, have 6.14 cutting blades. For example, if the diameter of a reamer does not exceed 10 mm, the number of blades is 6, for reamers with a diameter of 11.19 mm, the number of blades is 8, etc. A large number of cutting blades, small cut thickness (depth of cut t = 0.1-0.4 mm) and the presence of a gauging part ensure high processing accuracy.
When reaming and reaming, the depth of cut t = (D d) / 2.
Countersinking. They are used to obtain conical and cylindrical recesses for the heads of screws and bolts, in pre-machined holes (Fig. 2 d, e). Processing is performed with countersinks and countersinks.
Bowing. Used for processing flat surfaces from the end of the hole, which serve as support surfaces for fasteners. This type of machining ensures that the axis of the hole is perpendicular to the bearing surface. Processing is carried out by countersink-trimming, counterbore (Fig. 2 e).
Thread cutting. The machine method (on machines) is used to cut triangular threads of all sizes in through and blind holes. Processing is carried out by machine or machine-hand taps (Fig. 2 g).
Boring. As a rule, they are used for processing large holes (more than 40 mm), previously prepared by drilling or obtained in workpieces by casting, forging or stamping, as well as holes of non-standard sizes for which there is no axial tool. Most often boring is used for machining holes in body parts. Processing is performed with boring cutters with one blade or a multi-blade tool (blade cutters, etc.). Boring is used as preliminary processing of workpieces (roughness parameter Ra = 6.3. 12.5 microns and accuracy according to 10.13 grade) and as final (roughness parameter Ra = 0.2. 0.8 microns and accuracy according to 5.7 mu quality).
Boring shaping is carried out according to the method of traces: the guide circle 2 is reproduced by the rotary movement of the tool, which is the main cutting movement and determines the cutting speed v. The translational movement of the tool (feed movement) reproduces the straight line. generating 1.
Types of holes and their purpose
On vertical drilling and jig boring machines, cylindrical, conical, threaded and stepped holes are obtained and processed (as a rule, in workpieces that are not bodies of revolution). The holes in the parts have a different service purpose. They are used to connect parts into units, install fasteners (bolts, screws, pins, studs, washers), etc.
Technological equipment and its purpose
On a vertical drilling machine, holes of low accuracy are processed by drilling, reaming, countersinking, reaming, countersinking, counterbore and threading.
On a jig boring machine, as a rule, boring of high-precision holes is performed, the centers of which are strictly coordinated with respect to the base surfaces of the workpieces, as well as processing with an axial tool: countersinking, reaming, countersinking, counterbore, etc. In addition, the machine can perform marking, control of linear dimensions of the processed surfaces and center-to-center distances. Jig boring machine allows you to machine body parts.
The main units of the vertical drilling machine model 2H125.
Column 3 is fixed on the foundation slab 1 (Fig. 3), on the vertical guides of which there are table 2 and drilling head 6. The table and drilling head can move along the guides of the column. A spindle is located in the drill head, in which the cutting tool is installed. Feed box 4 and speed box 5, change the vertical feed and the spindle speed, respectively.
The main units of the jig boring machine model 2B440A.
On the machine bed 1 (Fig. 4) there is rigidly fixed a rack 2 with a boring head 3. Along the bed guides in the longitudinal direction slide 6 move, along the top of which the table 5 moves in the transverse direction. The table and slide are equipped with rolling guides. The machine has an optical reference system for the movements of the table and slide, which ensures the guaranteed accuracy of setting their coordinates (0.004 mm). The boring head contains a gearbox and a spindle vertical feed drive 4.
Installation of workpieces and cutting tools on machine tools
When machining on vertical drilling and jig boring machines, workpieces are installed and fixed on the machine table using universal or special devices (Fig. 5). The method of fixing the workpiece is chosen depending on its shape and size.
Clamping strips are used when fixing workpieces of complex shapes or large overall dimensions in the conditions of single-piece manufacturing of parts (Fig. 5 a). When processing through holes, the workpiece is placed on shims, which provides free exit of the tool from the hole.
Installation on a prism and fastening with a clamp (or clamping bars) is used when machining holes on the cylindrical surface of a workpiece such as a shaft (Fig. 5 b). Long workpieces (eg shafts) are mounted on two prisms. A machine vise is used to set and secure small-sized workpieces with flat ends (Figure 5 c). When processing through holes, the workpiece is placed in a machine vise on shims.
Fastening in a three-jaw chuck is used when machining holes in the ends of workpieces having a cylindrical shape (Fig. 5 d). The chuck is attached to the machine table.
On a vertical drilling machine, when installing a workpiece, it is necessary to ensure that the axis of rotation of the spindle coincides with the axis of the hole being machined. This is achieved by aligning the tip of the drill with the marked and punched center of the hole by moving the workpiece along the machine table.
On a jig boring machine, to set the table with a fixed workpiece in a position at which the base starting point coincides with the spindle axis, a center finder is used, as well as optical devices for counting the coordinates of the table and slide movement. This ensures the production of holes with a high accuracy of center distances (up to 0.004 mm) and high accuracy of their shape.
The way of mounting the cutting tool on a vertical drilling machine depends on the shape of the shank and the working conditions. Tools with a taper shank 1 are installed directly into the spindle 2 of the machine (Fig. 6 a) or with the help of reducing taper bushings 3 (Fig. 6 b) if the size of the taper of the tool shank is less than the size of the tapered bore of the spindle. A tool with a cylindrical shank 4 is installed in a collet 5 (Fig. 6 c) or a cam 6 (Fig. 6 d) drill chucks. If a sequential change of tools is required, quick-change chucks 7 are used (Fig. 6 d).
The reamer is fixed in swinging, floating or self-aligning chucks, which, during operation, allow the tool to be freely positioned along the hole and have an accurate direction. When threading in through holes, taps are fixed in quick-change, swinging and floating chucks, and in blind holes. in a safety chuck.
On a jig boring machine, a cutting tool (drill, countersink, etc.) with a tapered shank 1 (Fig. 7) is installed in the machine spindle 2 in adapter sleeves 3 (Fig. 7 a, b), and with a cylindrical shank 4. in a holder with a collet 5 (Fig. 7 c).
Boring cutters 1 (Fig. 8) on a jig boring machine are installed in cantilever holders 3, fixed in the spindle 2, with an inclined (Fig. 8 a) or straight (Fig. 8 b) installation of the cutter, as well as in a universal tool holder, design which allows for mechanical feed in the radial direction while the spindle is rotating.
Reaming holes. types and features of the operation
Deployment, which is a fairly common technological operation, is performed in cases where a previously prepared hole in a metal product must be brought to meet the required parameters. These parameters, in particular, include the shape and size of the hole, the roughness of the surface that forms it.
Connecting rod bore machining with a sliding reamer
The tool with which the deployment is performed manually or using a drilling machine is called “reamer”. Such a tool could be:
- manual and machine. depending on how it is used;
- cylindrical and conical. depending on its own configuration and shape of the hole being machined;
- tail and mounted. by the method of fixation;
- with a uniform and uneven arrangement of cutting teeth around its circumference for the formation of machined surfaces with varying degrees of roughness.
Types of metal reamers
The hand and machine tools used for deployment have certain differences in their design. Thus, a hand-held reamer is distinguished by elongated cutting edges on its working part and a square shank, with which the reamer is installed in the wrench. The design of the machine tool, which allows reaming of holes of considerable depth, has a shorter working part and a longer neck.
When choosing a reamer for hole machining, the following technical parameters are relevant:
As a rule, for a rough reaming, an allowance of one tenth to fifteen hundredths of a millimeter is required, and for a finishing one. from five hundredths to one tenth of a millimeter.
In order to understand in more detail how the deployment is carried out, you can consider the procedure for carrying out such a technological operation using a specific example. To obtain a hole with a diameter of 30 mm, first use a drill with a diameter of 15 mm, then ream the resulting hole to a diameter of 29.8 mm. It is processed with a rough reamer with a diameter of 29.95 mm, and after that, finishing is performed using a tool with a diameter of 30 mm, with which an allowance of 0.05 mm is removed.
Hole machining sequence
How high the accuracy of the hole obtained during reaming, as well as the degree of roughness of its surface, is significantly influenced not only by the geometric parameters of the tool used, but also by the type of cutting fluid used during processing. When reaming holes in steel parts, special emulsions mixed with mineral oil are used as such a liquid. When processing bronze and brass parts, mineral oils are not added to the coolant.
Conical hole machining
With the help of the technological operation of reaming, conical holes can also be processed, which previously had a cylindrical shape or were drilled with shoulders, for which drills of different diameters were used. Making a preliminary hole with shoulders in such cases allows you to leave a smaller allowance for further reaming.
The implementation of the deployment of tapered holes is practically no different from the technological scheme for processing cylindrical holes. To perform such a technological operation, as a rule, a roughing, intermediate and finishing tool is used.
Tapered hole machining sequence
A special taper gauge is used to check the results of this deployment. In this case, the check is carried out both along the plane of contact of the surfaces of the formed hole and caliber, and along the depth of passage of the control tool.
Gauge tapered center holes (KKTsO)
Such a check is carried out according to the following scheme.
- Several pencil lines (usually 3-4) are applied to the lateral surface of the cone gauge along its axis, placing them at approximately the same distance from each other.
- Using slight pressure, the gauge is inserted into the tapered hole in the part.
- Then the gauge is turned 1/3 turn.
- Having taken out the caliber, they control the condition of the pencil lines applied to its surface.
The fact that the deployment operation was performed efficiently is evidenced by the uniform erasure of pencil lines on all sections of the lateral surface of the caliber.
When reaming holes in workpieces made from different materials, you can use the following recommendations for choosing a coolant:
- steels belonging to the category of carbonaceous, structural and instrumental. water solution of soap, emulsion, sulfurized oil, mixture of oils;
- cast iron. can be processed without coolant or using kerosene;
- copper. emulsion;
- aluminum. emulsion, mixture of oils, pure kerosene, mixture of kerosene with turpentine oil, rapeseed oil.
- bronze. processed without using coolant.
Coolant compositions used for reaming holes in various materials
How Machine Deployment Works
You can use special tables to select the modes for performing machine deployment. The initial parameters in this case are the diameter of the hole being formed, the grade of the material to be processed, and also the material from which the reamer is made. The main modes of reaming performed by a machine are the cutting speed and the frequency with which the equipment spindle should rotate.
The maximum cutting speed, as a rule, is used when processing normalized steels, the minimum. when reaming holes in viscous materials.
Use of hand tools
Manual countersinking and deployment is carried out according to a similar scheme, which implies the following technological operations.
- Based on the parameters of the starting and ending hole, a tool is selected for performing a rough and fine reaming.
- The workpiece is securely fixed in a vice, if its dimensions allow it to be done. If it is significant in size, then it is not fixed before deployment.
- A tool for rough reaming is inserted into the hole in the part, which was previously obtained during the casting of the workpiece or its drilling.
- On the shank of the tool, which has a square cross-sectional shape, a wrench is put on.
- The outer surface of the reamer and the inner surface of the hole are lubricated with a special liquid.
- The reamer, using a wrench, begins to rotate in the direction of the location of its cutting edges. During the rotation of the tool, which should be performed slowly, without sudden movements, lubricant is constantly applied to its working surface. Rotating the reamer, it is necessary to carefully feed it in the direction of the processing, which ends after the metal layer left on the allowance is completely removed from the inner surface of the hole.
- After the rough reaming is completed, the tool is carefully removed, and it is not allowed to perform its reverse rotation.
- A finishing tool is placed in the hole machined with a rough reamer, on the square shank of which a knob is also inserted.
- The reamer for finishing is rotated clockwise, while this rotation is carried out very smoothly and accurately, constantly using lubricant. The amount of feed of the tool, in order to obtain a hole with the required parameters of the roughness of the inner surface, must be minimal.
- After finishing finishing, the reamer is removed from the hole and its geometric parameters are checked using a smooth limit plug gauge.
Manual deployment techniques
Some nuances of machine deployment
It is very important to properly prepare the hardware before machine deployment. Such preparation consists in the following.
- The taper of the tool shank and the bore in the machine spindle are thoroughly wiped.
- The reamer is inserted into the spindle in the same way as a taper shank drill.
- The workpiece is fixed on the equipment work table so that the axis of the hole exactly coincides with the axis of the tool used.
Machining a hole on a machine with a carbide reamer
The deployment process itself, for which a roughing and finishing tool is used, is performed in the following sequence:
- After completing drilling of the workpiece to be processed, the drill in the spindle of the drilling equipment is replaced with a rough reamer.
- Conducting a rough rollout.
- The roughing tool is replaced with a finishing one and the hole pattern is repeated.
- After final deployment, the tool is taken out of the processing area, the machine’s electric motor is turned off and the result of the work is checked using a plug gauge.
In some cases, for fine reaming, floating chucks or articulated mandrels can be used, in which the cutting tool is fixed.
Drilling, countersinking and reaming
Drilling. this is the process of obtaining by cutting deaf and through-
cylindrical holes in solid material, carried out on drilling and turning machines. If the diameter of the hole that you want to get during the processing is 30 mm, then two drills are used to make it. First, for drilling. and the second, for reaming.
Drilling (reaming) is rough machining of holes, during which accuracy is ensured within 12. 14 grades and roughness microns.
In our country, a unified gradation of drill diameters is adopted, regulated by GOST 885-77 and covering almost all hole sizes up to 80 mm found in machine parts and devices.
The following types of drills are produced: spiral, feather, single-sided cutting (gun), annular and combined [11, 13].
Spiral or twist drills are most widespread when machining holes with a depth of up to (5. 10) d. The design of a twist drill with a taper shank is shown in Fig. 40.
Fig. 40. Taper Shank Twist Drill Design
The twist drill consists of a working part and a shank. On the working part, in turn, the cutting part and the guiding part can be distinguished. A foot is provided for knocking out drills with a taper shank from the spindle bore.
Between the working part and the taper shank of the drill, there is
often has a neck-like transitional part of the drill.
Twist drills can have a cylindrical shank (at a diameter of mm) or a taper shank (at a mm).
Date added: 2016-12-16; views: 2584; ORDER WRITING WORK
“Drilling, countersinking, countersinking and reaming holes
In the work of a locksmith for the manufacture, repair or assembly of parts of mechanisms and machines, it is often necessary to obtain a variety of holes in these parts. For this, the operations of drilling, countersinking, countersinking and reaming of holes are performed.
The essence of these operations lies in the fact that the process of cutting (removing a layer of material) is carried out by rotational and translational movements of the cutting tool (drill, countersink, etc.) relative to its axis. These movements are created using manual (brace, drill) or mechanized (electric drill) devices, as well as machine tools (drilling, turning, etc.).
Drilling is one of the types of making and machining holes by cutting using a special tool. a drill.
Like any other cutting tool, the drill works like a wedge. By design and purpose, drills are divided into feather, spiral, centering, etc. In modern production, mainly twist drills are used and, less often, special types of drills.
On the guide part there are 2 screw grooves, along which the chips are removed during the drilling process. The direction of the helical grooves is usually right-handed. Left hand drills are rarely used. The narrow stripes on the barrel of the drill are called ribbons. They serve to reduce the friction of the drill on the hole wall (drills with a diameter of 0.25-0.5 mm are made without ribbons).
The cutting part of the drill is formed by 2 edges located at a certain angle to each other (corner at the top). The size of the angle depends on the properties of the material being processed. For steel and cast iron of medium hardness, it is 116-118 °.
The shank serves to fix the drill in the machine spindle or drill chuck and can be tapered or cylindrical. The tapered shank has a foot at the end, which serves as a stop when pushing the drill out of the socket.
The neck of the drill connects the working part and the shank and serves to exit the abrasive wheel during the grinding of the drill during its manufacture. Drill grade is usually affixed to the neck.
Drills are made mainly of high-speed steel or hard sintered alloys of grades VK6, VK8 and T15K6. Only the working (cutting) part of the tool is made of such alloys.
In the process of work, the cutting edge of the drill becomes dull, so the drills are periodically sharpened.
Drills produce not only blind (pre-drilling) and through holes, i.e. obtaining these holes in solid material, but also reaming. increasing the size (diameter) of the holes already obtained. Pen drills are the simplest in design. They are used in the processing of hard forgings, as well as stepped and shaped holes.
A special group of drills is made up of center drills designed for machining center holes. They are simple, combined, combined with a safety cone. Simple twist drills differ from conventional twist drills only in the shorter length of their working part, since they drill small holes. They are used when machining high-strength materials, while combination drills often break.
Countersinking is the treatment of the top of the holes in order to obtain chamfers or cylindrical recesses, for example, for a countersunk screw or rivet.
Countersinking is performed using countersinks or a larger diameter drill;
Countersinking is the processing of holes received; by casting, punching or drilling, to give them a cylindrical shape, improve accuracy and surface quality. Countersinking is performed with special tools. countersinks.
Countersinks can be with cutting edges on a cylindrical or conical surface (cylindrical and conical countersinks), as well as with cutting edges located at the end (end countersinks). To ensure the integrity of the hole being machined and the countersink, a smooth cylindrical guide part is sometimes made at the end of the countersink.
Countersinking can be a finishing or pre-deployment process. In the latter case, when countersinking, leave an allowance for further processing.
Reaming is the finishing of holes. In essence, it is similar to countersinking, but provides higher accuracy and low roughness of the surface of the holes.
Hole reaming tool. reamer. Hand reamers have a square end on their tail for rotating them with a knob. On machine reamers, the shank is tapered.
For the processing of tapered holes, a set of conical reamers of three pieces is used: roughing (roughing), intermediate and finishing. Smooth cylindrical holes are processed with reamers with straight grooves. If there is a keyway in the hole, then tools with spiral grooves are used to deploy it.
When working on drilling machines, various devices are used to secure workpieces and cutting tools.
Machine vise. a device for fixing workpieces of different profiles. They can have replaceable jaws for clamping complex parts.
Prisms are used to fix cylindrical workpieces.
Drill chucks are used to fix cutting tools with cylindrical shanks.
Using adapter sleeves, cutting tools are installed in which the size of the shank taper is less than the size of the machine spindle taper.
On drilling machines, all basic operations for receiving and processing holes by drilling, countersinking, countersinking and reaming can be performed.
Vertical drilling machines are used for drilling holes up to 75 mm in diameter. They can provide reaming, countersinking, reaming and tapping operations.
Bench drilling machines are used for drilling small parts of holes up to 12 mm in diameter.
Safety precautions when drilling metal:
Technological methods of processing holes
Holes can be machined with or without chip removal. Consider the methods of making holes with a razor tool. They are drilling, countersinking, reaming, boring, broaching.
This is a technological process of obtaining through or blind holes in a workpiece with a blade tool (drill) with a rotary main cutting movement at a constant radius of its path and feed only along the axis of the main cutting movement (Fig. 11.32, and).
Fig. 11.32. Hole processing methods using:
and. drill; b. countersink; in. sweeps
Drilling is also used for reaming to a larger diameter of existing ones and obtaining centering holes. The drilled holes do not have the correct shape: their cross-sections are oval, and the longitudinal ones are conical.
Drilling provides 11-12th grade of accuracy and roughness of the machined surface Rz = 80 ÷ 20 μm. The range of used drill diameters is in the range from 0.15 mm to 250 mm (for plate).
Drilling, turning and boring machines are used for drilling.
The drilling method in a drilling machine is characterized by a stationary position of the workpiece and a rotational-translational movement of the tool (see Fig. 11.32, and). When working on lathes, the rotary (main) movement is made by the workpiece, and translational along the axis of the hole (feed movement). by the drill (see Fig. 11.5, e). When drilling, use both standard drills with two cutting edges (Figure 11.33) and special (Figure 11.34).
Fig. 11.33. Standard drill parameters
Fig. 11.34. Types of special drills:
and. first; b. for deep drilling; in. for core drilling
To obtain holes of higher accuracy and surface finish, after drilling, countersinking and reaming are performed on the same machine.
It is a technological method for machining pre-drilled or cast or stamped holes to give them a more regular geometric shape, improve accuracy and reduce roughness. Countersinking is carried out with a blade tool. a countersink (Figure 11.32, b), which has a harder working part than a drill. Countersinks have three to eight teeth. The accuracy of the holes is within the 10-11th grade and roughness Ra = 10 ÷ 15 μm.