Drilling machine instructions
Performing operations on drilling machines is an uncomplicated process. This can be learned quite quickly. However, certain conditions must be met in order to work effectively and safely on the equipment:
- All rotating, moving machine parts as well as work pieces should be reliably secured to avoid personal injury and conductive parts should not pose a hazard to people nearby.
- To produce high-quality holes, cutting tools of the machine must be properly sharpened, and precisely suited to the material of the workpiece and the type of operation.
- To prevent rapid wear and breakage of cutting tools in case of intensive heating, they should be periodically cooled down by special liquid or water.
- To prevent the cutting tool from jamming when making deep holes, it is necessary to periodically take out the working tool, remove chips accumulated in the hole, and then continue working.
It is appropriate to start the rating description with model “Instar” SSV 63500. This machine has special fixtures for the working surface. clamping is performed as reliably as possible. Basic configuration allows to start working immediately after installation. There is no special noise during the operation of such a machine, which has a solid body.
The work table is relatively small. Technical parameters:
- power. 0.35 kW;
- net weight. 13 kg;
- 5 functional speeds;
- there is no provision for the supply of cooling lubricant;
- spindle cone is of MK-2 type;
- Reverse is not possible;
- The working area is 16×16 cm;
- Asynchronous actuator.
An alternative model is Patriot SD 370. No problem with lowering or raising the spindle, thanks to the cleverly designed handle. The housing perfectly protects the working nodes from mechanical deformation and water penetration. Weighs this machine weighs 12.5 kg. Its base is designed properly and is not subject to vibration.
Overloading is almost no problem. Model is designed for both metal and woodworking. The only problem is difficult to replace accessories. The chuck is of the key-type. It has 5 working speeds and weighs 13.6 kg.
Elitech STS 3 in its characteristics at least as good as the just described models. It confidently works with wood, metal, and plastic. Spindle speed can be varied from 290 to 2580 in 60 seconds. There is an electromagnetic switch. Special illumination system allows to work even in places with insufficient initial illumination.
Table can be tilted up to 45 degrees left and right. No sparks or chips flying around thanks to the light shield. Designers have provided a laser guidance system. Machine requires 220 V voltage for operation. On the whole, you get a reliable and safe product, the only disadvantage of which is a bit weak casing.
You have to pay more for a modern professional device. In this case the Euroboor ECO is a good choice. 60S. Coordinate control panel for easy operation. The motor power is noticeably higher than in the previous case. 1.6 kW. Machine to be moved in original carrying case, hexagonal keys, chain for safety, etc. п.
The Fortezzo SCY-42HD operates from a household electrical outlet in no time at all. This machine can drill a wide range of materials. Its important features are:
- current consumption. 1.7 kW;
- The only speed available;
- The maximum drilling diameter is 5 cm;
- 19-millimeter Weldon-format chuck;
- Speed of operation. from 100 to 730 rpm.
It is quite reasonable to complete the review on the Bosch PBD 40. An advanced manufacturer has provided control with a special display. The quality and accuracy of assembly do not cause criticism even from the most picky consumers. Built-in laser is very useful in practice. Main features:
- current consumption. 0,71 kW;
- 2 working speeds;
- Working with steel workpieces up to 1.3 cm thick;
- work with wooden workpieces up to 4 cm thick;
- quick-action chuck.
Machining with an axial tool
Machining on drilling machines.
Drilling, reaming, countersinking, reaming, countersinking, tapping, threading, and machining of difficult holes are performed on the drilling machines.
For simultaneous machining of several holes, multi-spindle vertical drilling machines are used. Spindles on these machines are installed in the drilling head, depending on the location of holes in the workpiece.
Boring a through hole.
The cutting tool is a twist drill. Depending on the accuracy and batch size of the workpieces to be machined, holes are drilled on the guideway or according to markings.
Reboring is the process of increasing the diameter of a previously drilled hole with a larger diameter drill. The diameter of the bore for reaming is selected in such a way that the transverse cutting edge does not interfere with the work. In this case the axial force is reduced.
Countersinking is the machining of previously obtained holes to give them a more regular geometric shape, increase accuracy and reduce roughness with a multi-blade cutting tool. countersink.
reaming. final machining of a cylindrical or tapered hole with a reamer (usually after countersinking) to obtain high accuracy and low surface finish.
Countersinking is face grinding of the bore face with a countersink to achieve perpendicularity of the flat face surface to its axis.
Countersinking makes cylindrical or conical cavities in existing holes for the heads of screws, bolts, rivets and other parts. The following picture shows countersinking a cylindrical countersink (countersink) and a conical countersink with a conical countersink.
Thread cutting is making a helical groove on the inner cylindrical surface using a tap.
Holes with complex profiles are machined with the combined cutting tool.
Drilling of deep holes (hole length exceeding five diameters) is performed on special horizontal drilling machines. When deep holes are drilled with helical drills, drill drift and hole breaking occur, making it difficult to supply coolant and evacuate swarf. Therefore, for drilling deep holes, special drill bits (cannon drill, feather drill, ejector drill, etc.) are used.). Coolant is supplied to the cutting zone and flushes chips through the drill’s inner passage.
Part machining on drilling machines also involves the creation of various threads. Tapping is usually done with wrenches or machine taps. The latter require subsequent ejection from the hole, which must be taken into account during tapping.
When working with nonferrous alloys and ductile steels, self-tapping taps are often used. They can be used for holes up to 36 millimeters in size.
Countersinking is the machining of countersinks necessary for masking the head of fasteners. Countersinking is carried out by means of a centering tool. This is for holding two axes in alignment.
Counterbore tapping refers to the machining of the surfaces of the bosses that support wrenches and screw heads. It is very important that the stem of the fastener does not deform during the tightening process. This involves checking the position of the face, which must be perfectly perpendicular to the axis. A special tool called counterbore is supplemented by a special guide tool.
The process of working on a drill press can be very different. This type of equipment is distinguished by its wide functionality and high precision. That is why the scope of application of a drilling machine is quite considerable. But we have considered only the main areas of use of this metal-cutting equipment.
.10. Drilling and reaming. Drilling machines
Drilling is called making a circular hole in a product or material using a special cutting tool, a drill, which in the process of drilling has both rotational and translational motion along the axis of the drilled hole. Drilling is used primarily when making holes in parts that are connected during assembly.
When working on drilling machine The drill bits perform a rotary and translational movement with the workpiece stationary. Turning, automatic or turret-type lathes turn the workpiece while the tool moves with only a translational motion.
The following machining operations are used, depending on the degree of accuracy required: drilling, reaming, countersinking, reaming, boring, countersinking, centering.
Drilling machines are used for the following processes: drilling, reaming, countersinking, reaming, counterboring, facing, counterboring, countersinking, tapping.
Drills with conical or cylindrical shank, tapered adapter sleeves, drill knockout wedges, two- and three-jaw self-centering drill chucks, drill bit mounting handles in chucks are used for drilling operations, quick-clamp chucks, spring chucks with automatic drill cutoff, machine vices, boxes, prisms, jaws, squares, hand vices, tilting tables, and all kinds of devices, manual and mechanical drilling machines and drills.
A distinction is made between manually and mechanically operated drilling machines. Manual drilling machines include: jigsaws, drills, ratchet drills, and hand-held drilling rigs. Power-driven manual drilling machines include electric and pneumatic drills, which allow drilling in hard-to-reach places by using special shanks.
Power-driven drilling machines include vertical drills, radial drills, horizontal boring drills and special-purpose drills. Vertical drilling machines may have devices for using multi-spindle heads. Special-purpose drilling machines can be unit, multi-position or multi-spindle machines.
The vertical drilling machine differs from other drilling machines in that it has a bed with vertical guideways on which the machine table can move. In addition, it has a feed mechanism, a pump for supplying coolant, as well as a speed box for obtaining different speeds of the drilling spindle of the machine.
Vertical drilling machines (depending on the type) can drill with up to 75 mm diameter holes, workbench drilling machines with up to 15 mm diameter drill bits, table top drilling machines with up to 6 mm diameter drill bits. Manual electric drilling machines (depending on the type) can drill holes with a diameter of up to 25 mm, manual pneumatic drilling machines. with drill bits up to 6 mm in diameter.
Drill ratchets are used for drilling holes in hard-to-reach places in steel structures. The manual drive by the oscillating movement of the ratchet lever generates the rotation of the drill bit and its feed along the hole axis.
The disadvantage of ratchet drilling is the low productivity and high labor intensity of the process.
Drill bits. these are cutting tools used to make cylindrical holes
a. twist drills; b. feather drills
According to the design of the cutting part of drills are divided into feather drills, with straight grooves, spiral drills with helical grooves, drills for deep drilling, center drills and special drills.
Spiral drill bits depending on their performance are divided into twisted, milled, cast (for large diameters), with plates of metal carbide alloys and welded.
Drills are made from tool carbon steel U10A, U12A, alloy steel 9ÕÑ or high-speed steel R18, R9, РЭМ. Drill bits lined with tungsten carbide and titanium carbide alloy plates are often used.
Spiral drill holes are used for high accuracy requirements, holes for further processing by reaming, boring or broaching, holes for tapping (Tab. 7).
Accuracy of hole machining
Spiral drill bits consist of a shank and a working part, which is divided into a guide part and a cutter part. Between the guiding part and the shank lies the neck.
Shank. is a part of the drill bit of cylindrical or conical shape (wood drill bits have a tetrahedral conical shank), which serves to fix the drill bit in conical form in conical adapter sleeves with Morse cone, and in cylindrical form. in a two- or three-cone drill chuck. The end sleeves and the drill chuck are fastened in the bore of the spindle. Cone shanks end in a foot that is used to knock the drill out of the spindle or tapered adapter. Cylindrical shank ends with a shank guide. Drills with square shanks are most commonly used with ratchet or hand-held rotary tools for drilling holes. Core bits with a cylindrical shank usually have small diameters (up to 20-30 mm).
The working part of the drill bit consists of a guide part and a cutting part.
The guide part of the drill bit. is the part between the neck and the cutting part. It serves to guide the drill along the axis of the hole. The guide part has screw grooves for chip evacuation and a drill stem. There is a ribbon on the outside screw surface of the drill guide part.
Cutting part of the twist drill bit consists of two cutting edges connected by a third edge. the so-called crosspiece.
Ribbon is a narrow band along the helical groove that runs down smoothly to the shank. The purpose of the tape is to absorb some of the friction of the drill bit against the hole wall that occurs when the tool enters the material. The drill bit diameter is measured by the distance between the ribbons.
The value of the helical flank angle depends on the material to be cut (table “Angle of inclination” of the helical flank of the drill bit). 8).
Recommended drill tip angles
The process of cutting metal with a cutting edge is carried out by plunging it into the metal under the influence of the rotation of the drill bit and its axial feed. The size of the cutting edge angle is determined by the angle of the helical line and the back angle of the drill. The required feed force and cutting force are determined by the value of the rake angle and the value of the cutting edge. The feed effort required for drilling can be reduced by sharpening the traverse edge (bridge) and selecting the optimum cutting angle for the material.
If the drill bit is not cutting well, it should be sharpened. Sharpening can be done manually or by machine. Properly sharpened drill bits produce the necessary angles, lengthen the life of the drill bit, reduce effort, and make it possible to produce properly made holes.
Selecting the necessary cutting angles for the material and sharpening on special drill sharpening machines ensures correct cutting angles and the position of the transverse edge in the center of the drill. After sharpening, the sharpening angles can be checked with an angle gauge or a template.
Jet drills (fig. 21, б) are usually made of carbon tool steel U10A or U12A. These drills differ in the following elements: double-sided cutting part with the angle of 116°, single-sided. with the angle of 90-120°, guiding part with the angle of 100-110°, tapered working part, neck and shank.
The double-sided cutting part ensures the working motion with the drill bit rotating in both directions. The one-sided cutter section allows the drill bit to operate in one direction only.
The disadvantage of these drills is the lack of a guide and the change in diameter with each sharpening. Used for holes of small diameter, which do not require high accuracy of execution.
Drill bits with extended guide part ensure better guidance and more accurate size of the hole, make it possible to get the same diameter until the guide part is ground. However, these drills are unproductive.
Before drilling, the material (marking and marking of the drilling locations), the tools and the drilling machine must be prepared accordingly. Once the workpiece has been clamped and checked on the drill table or in another fixture and the drill bit has been clamped in the spindle of the machine, the drills can begin according to the instructions and safety requirements. Not to forget the drill bit cooling.
During drilling various defects can occur: breakage of the drill bit, chipping of the cutting edges, deviation of the drill bit from the hole axis, etc. д.
In Tab. 9 the types of faults, why they occur, and how they can be eliminated.
A drilling jig is a fixture with conductor plate that can be used to machine a large number of identical workpieces with identical hole patterns without the need to pre-digitize the holes. Drill jigs come in a variety of designs. They can be installed on the part and fastened directly to the workpiece, or it can be a fixture with a conductor plate in which the workpiece is placed and fastened. In this case, the conductor plate contains holes with hole sleeves of a specific hole diameter inserted in the holes, through which the drill is guided into the workpiece that is clamped in the drilling fixture. In some cases, the conductor plate has holes without conductor bushings.
Rice. 22. Core drilling fixture with conductor hole plate: 1. drill bit; 2. bushing; 3. conductor plate; 4. bottom of conductor; 5. workpiece; 6. wing nut screw
When drilling, cooling and the coolants used play an important role. Coolant has three main functions: it lubricates the cutting tool, the drill bit, the workpiece metal and the chips, cools the metal, intensively dissipates the heat generated in the cutting zone and facilitates chip removal from this zone.
Coolant is used in all types of metal machining. A good coolant does not corrode the tool, attachment or part, has no harmful effect on human skin, has no unpleasant smell and conducts heat well. When drilling steel holes, emulsion emulsion E-2 or ET-2 in 5% solution of water soap, emulsion E-2 or ET-2 in 5% solution or the following liquid is used: oil “Industrial”. 50%, kerosene. 50%, when drilling aluminum. While drilling shallow holes in cast iron no coolant is used. When drilling deep holes in cast iron, compressed air or a 1.5% solution of emulsion E-2 or ET-2 is used. When drilling copper and copper-based alloys the 5 % emulsion solution E-2, ET-2 or Industrial oil is used.
To get holes with diameter over 30 mm in metal or a workpiece, it is necessary to apply double drilling. The first operation is carried out with a drill diameter of 10-12 mm, the second. with a drill of the required diameter (reaming). Drilling with two reaming or drilling, reaming, and countersinking greatly reduces cutting forces and operating times.
Remove a broken drill bit from the hole being drilled by twisting it backwards with tongs (if there is a protruding part of the drill bit). If a broken drill bit is inside the material, the workpiece to be drilled is heated together with the drill bit until it turns red, and then gradually cooled. The released drill bit can be unscrewed with a special tool or drilled out with another drill bit.
Center drill is a tool used to make center holes in the end faces of shafts. A distinction is made between two types of pilot drill bits: drills for usual center drill holes without pilot taper and drills for center drill holes with pilot taper The normalized angle for usual pilot drill bits is 60°, drill bits with pilot taper are 60 and 120°.
Fig. 23. Center drills: a. ordinary drills without safety cone; b. drills with safety cone
On large and heavy shafts, centring countersinking at the ends is achieved in three steps: drilling, countersinking at 60° and countersinking of the safety cone at 120°.
Countersinking. is to increase the diameter of a previously drilled hole or to create additional surfaces. The machines used for this operation are countersinks, with a cylindrical, tapered, end face or shaped surface
The purpose of countersinking is to create appropriate fits in holes for rivet, screw, or bolt heads, or to align end surfaces.
a. cylindrical for countersinking of through or deep holes; b. conical for chamfering and forming conical recesses; c. end drills for countersinking of end surfaces (facing); d. shaped drills for countersinking of shaped surfaces
Countersinks are made from carbon tool steel U10A, U12A, alloy steel 9ÕÑ or high-speed steel R9, R12. They can have brazed hard alloy cutting plates. Countersink shanks and tool bodies are made of 45 or 40X steel.
Countersinks can be solid cylindrical, conical, shaped, welded with a welded-on shank, solid on the head, prefabricated on the head. Countersinks of small diameters are usually solid, while countersinks of larger diameters are welded or are fitted. Cone countersinks have apex angles of 60, 75, 90 or 120°.
Counterbore. is a multi-blade cutting tool used for finish machining of holes to get a hole with high accuracy and roughness of the surface.
Reamers are subdivided into roughing and finishing tools. Final reaming ensures the accuracy of 2 to 3 classes (qualification 10-7), and when executed particularly thoroughly. 1st class (qualification 6-5) with surface roughness 7-8 of the purity class (roughness height of 1.25-0.32 microns).
Reaming gives the final size of the hole, required by the drawing. Diameter of the bore for reaming should be less than the final size of the allowance for reaming (Tab. 10).
Diameter allowance for reaming after a drill, cutter, or countersink, mm
There are the following types of reamers: by the method of use. manual and machine, by shape. with a cylindrical or conical working part, by the accuracy of processing. roughing and finishing, by design. with a cylindrical shank, with a conical (Morse cone) shank and attachable. Bearing reamers can be one-piece, with a replaceable bobbin, or floating. Hand reamers can be one-piece or split. Reamers can be designed with a simple serrated or helical pattern. In fig. 25 manual reamers are shown.
a. conical roughing; b. conical intermediate; c. conical finishing; d. cylindrical with straight teeth; e. cylindrical adjustable; f. cylindrical expanding
The number of teeth in a reamer depends on its diameter and purpose. Manual and powered reamers with straight teeth usually have an even number of teeth (e.g., 8, 10, 12, 14). Spiral toothed reamers have left-hand and right-hand cutting pieces.
14 Awesome Life Hacks for Drill Machine
Unclamped and adjustable reamers are used for repair work to reamer holes that have different tolerances, and for minimizing enlargement of an already-finished hole.
Three tapered reamers are included with Morse tapered sockets: a roughing reamer, an intermediate reamer, and a finishing (tapered) reamer.
Boiler reamers are used in boiler work to enlarge rivet holes.
The reamer has the following elements: a working part, a neck, and a shank (conical or cylindrical).
Hand-operated three-pen reamer shanks are fastened in fixed or adjustable jigs.
Reamers have non-uniform spacing of cutting edges: in order to improve the quality of the hole and to prevent its bevelling, the teeth are placed on the circumference at different distance from each other.
Coolant is used to cool the tool, reduce friction, and increase life of the cutting part of the tool. Table 11 shows the coolant compositions used for reaming in different materials. 11 shows compositions of coolants used for reaming holes in different materials.
Coolant used for reaming holes in different materials
Carbon tool steels U10A and U12A, alloy tool steels 9ÕÑ, ÕÂ, ÊÕÑÂÔ, high-speed steel Ð9 and Ð18, and also hard alloys T15Ê6 for treatment of steel, copper and other ductile metals and BK8 for treatment of cast iron and other brittle metals are used for reamers production. HSS reamers are made with welded shanks of 45 steel. Collecting, adjustable, and on-tool reamer bodies are made from structural steel.
Puncher. is a locksmith’s tool made of carbon tool steel U7 or U8, which is used for punching holes in sheet or strip metal or nonmetal materials not more than 4 mm thick.
b. hollow for leather and plastic
The working part of the punch can be round, rectangular, square, oval or other shapes. The leather and tin plate punch has a blind hole in the working part, which is connected to a longitudinal side hole that runs through the wall of the lower part of the punch. Waste is ejected through this hole.
Hole punching is carried out when some surface damage is allowed in the hole area and cleanliness and accuracy of execution of the hole is not required.
The following safety requirements must be observed when working on drilling machines.
Before starting work check technical condition of drilling machine and tools. The machine should be switched on and off with dry hands.
Work on the machine must be carried out in accordance with the operating instructions of the equipment as well as in accordance with the work safety instructions. Special work clothing must be worn and hair must be worn under the headdress.
Workpieces must be properly and securely clamped in a vice or fixture in good technical condition. When drilling small holes, the left hand holding the workpiece must oppose the direction of rotation of the spindle. Do not hold or brake the spindle, change speed and feed rate, or remove shavings from the table or workpiece while the spindle is in motion.
The drill should be cooled with coolant using a brush or watering. Do not cool with wet rags or cloths.
All breakages that can be repaired must be repaired by a trained worker.
If you use it a lot, it’s better to choose a machine with at least 0.6 kW. This is important even if you plan to work on thick hard metal or stone, or hardwood, at least occasionally. Normal household drilling machines are designed for a maximum of 1.6 cm. Semi-professional and professional equipment can make cuts up to 6 cm.
Do not think that only heavy machines develop considerable power. Relatively lightweight models with several working modes are also quite productive. You must pay attention to the level of safety.
If a machine does not have a protective screen, that is too bad. The prevention of unintentional start-up is considered a useful option.
You should always consider whether a particular model can fit in a certain room. Sometimes it is the size discrepancy that makes you give up on the purchase. And also it is necessary to consider whether the machine will be used permanently or periodically. Professional equipment is worth buying only if you work frequently and for a long time, at high rotation speed and with complex workpieces.
Reverser and backlighting almost always needed. Tilting the work table and laser sight are useful for experienced users who know how to use these options. The more speeds are available, the more practical the machine will be. A vise is considered a very useful addition, thanks to which you can drill particularly precise holes. And, of course, you have to consider the actual reviews.
The design of a drilling machine
The equipment can be domestic or professional. The first type is a desktop machine of compact size, which is installed on the surface of a workbench or other elevation. The basic design of a drilling machine consists of the following elements:
- Spindle headstock. Mounts the work chuck for securing the cutting tool.
- Drilling head. The design includes a spindle headstock, electric motor and belt drive.
- Columnar support leg. The drill head is mounted on it.
- Massive base plate. It is made by casting from steel or cast iron. Used as the base of the machine and to secure the vertical stand of the equipment.
- Drilling operation is performed by the movement of the spindle.
Algorithm of manufacturing
Given that by the type of processing home machines will be interchangeable, and the decisive role will be played by the attachment installed in the drill, let’s consider two basic options for homemade units. horizontal and vertical.
The order of assembling a vertical machine tool is as follows.
- Cut out a square foot from a piece of metal or wood, 50 cm by 50 cm, 10 to 20 mm thick.
- Exactly in the center, 1-2 cm from the edge, drill a hole to install the rack. The diameter of the stand must be at least 5 cm.
- Install the rack, center it with a level and weld with a welding electrode. If you make a wooden machine and the stand will be wooden, then fix it rigidly with self-tapping screws.
- Fasten the drill by means of metal clamps to the movable element, which will be put on the rack, forming the lowering/raising spindle.
- Put a spring on the table. Its length should be at least 2/3 of the stand.
- Having put the drill on the stand, mark the place where the drill will hit when the spindle is lowered.
- According to this place, cut out two through holes crosswise in the frame.
- Place the table on which the workpiece will be clamped is placed in the groove on the threaded pin. From the bottom side, a nut is screwed on the pin. It will fix the table in the required position. On the outer side, you can also fasten the table to the pin with a nut by sinking it into the surface of the table so that it does not interfere with the laying of the workpieces.
- It is important that after fixation with a nut the length of the outer part of a pin should be flush with the upper surface of the table.
Workpiece is placed on the table (if necessary, fixed with clamps) and moved along the rabbets in the required direction. The drill is lowered manually and raised again by the spring. To convert the machine into a milling or grinding machine, just replace the drill with the appropriate attachment. a cutter or a sanding block.
The assembly algorithm for the horizontal machine looks like this.
- Cut out a rectangular bed. the dimensions are determined individually.
- On one edge of the machine it must be fixed with a cavity in the upper part corresponding to the size of the instrument.
- Fix the drill on it with a clamp.
- Along the bed, cut a through hole for the pin, and along the edges set two metal corners, which will move the clamping sleeve.
- The width of the clamping sleeve must exactly match the distance between the guide angles (slides). The threaded pin is screwed into it from below. It will move inside the cavity.
- Having moved the bushing closely to the drill chuck, determine the place where the special headstock for workpieces fixing will be set.
- Attach a headstock to the sleeve with a tapered metal pin in the center.
- Hub is fixed in position (for workpiece clamping) by nut screwed on pin from below.
Just like the previous one, this machine can be used not only as a lathe, but also as a milling or grinding machine. Simply clamp the required work item. cutter, grinder, drill bit. into the drill chuck.
For both variants, special adjustable feet must be provided for the base.
If the bed rests flat on a workbench or table, the adjustment and locking of the clamping sleeve on a horizontal machine or of the workpiece table on a vertical one becomes impossible.
Drilling technology and tooling
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Not only can drilling be performed on the drilling machines, but also other technological operations of further processing of the holes. The following operations are carried out on modern drilling machines:
- drilling of through holes and blind holes (fig. 6.9, а);
- boring of holes to a larger diameter (Fig. 6, b); c); d); e); f); g); h). 6.9, б);
- countersinking, performed to obtain a hole with high qualification and roughness parameter of the surface (fig. 6.9, в);
- countersinking, performed to create flat-bottomed holes in the base of the drilled hole for screw and bolt heads (Fig. 6.9, г);
- reaming of cylindrical and conical bores, which provide high accuracy and roughness of processed surface (fig. 6.9, д);
- rolling out the holes with special mandrels with steel hardened rollers or balls to obtain a dense and smooth hole surface, and roughness Ra 0,63. 0.08 μm (Fig. 6.9, е);
- Tapping internal threads with taps (Fig. 6.9, ж);
- Undercutting (countersinking) ends of external and internal flanges to obtain smooth surface perpendicular to the hole axis (fig. 6.9, з).
Technological possibilities of drilling machines are not limited to the listed works. They can be used to flatten hollow rivets, process multi-faceted holes, and perform other operations.
Drilling holes are processed on drilling machines by various cutting tools: drills, countersinks, reamers, cutters, and taps.
To fix drill bits, reamers, countersinks and other cutting tools in the spindle of the drilling machine the following auxiliary tools are used: adapter drill sleeves, drill chucks, mandrels, etc.д.
Transitional tapered sleeves are used for fixing cutting tools with a tapered shank, when the cone number of the tool shank does not correspond to the cone number in the machine tool spindle, for example on lathe screw-cutting machines.
Outer and inner surfaces of the adapter sleeves are made with Morse cone with seven numbers from (0 to 6) according to GOST 8522-70. The sleeve together with the drill bit is inserted into a tapered seat of the machine spindle. If one sleeve is not enough, several adapter sleeves are used, inserting one into the other.
Drill chucks are used for fastening of cutting tools with a cylindrical shank with diameter up to 20 mm.
Tools are fastened in the three-claw drill chuck with a wrench (fig. 6.10, а). Inside the chuck housing (Fig. 6.10, b) three cams 1 with threads, united by a nut 2, are inclined. Sleeve 3 is rotated by a special wrench 4 inserted into the opening of the chuck body. When rotating the cage in clockwise direction the nut rotates simultaneously with it.
Clamping jaws, descending down, gradually converge and clamp the cylindrical shank of the drill bit or other cutting tool. When the cage rotates counterclockwise, the cams move upward and release the clamped tool.
Two cams in the double-drive drill chuck clamp the tool shank by moving two cams in the T-slots of the chuck. These jaws are brought together and apart with a wrench using a right- and left-hand threaded screw.
To clamp small diameter drill bits with cylindrical shanks collet chucks are often used.
Quick-change drill chucks are used to reduce the auxiliary time for drilling machines. They allow fast change of cutting tool without switching off the machine tool. One of such chucks designed for mounting of cutting tools with conic shanks is shown in fig. 6.11, я. For fixing drills with cylindrical shanks in the conical hole 6 of the chuck insert the adapter conical cut bushing (fig. 6.11, б). Recently in serial and mass production such sleeves are widely used for fixing drills with cylindrical shanks with a diameter up to 10 mm. This sleeve, inserted into the spindle of the drilling machine, provides a firm hold on the drill bit.
Self-aligning drill chucks are used for pre-drilled holes. Chucks allow centering a cutting tool along the axis of a machined hole.
Safety chucks are used to hold taps when tapping threads on drilling machines. Application of such chucks improves quality of tapped threads and protects the tap from breakage (fig. 6.12). The leading cam half-coupling 5 is pressed by the spring 6 to the driven coupling halves 2 and 4, which are free sitting on the mandrel 7. In this case the cams 3 located at the end of the coupling half 4 enter the hollows of coupling halves 2 and 5 and set them in motion. On completion of thread cutting in the hole, coupling halves 2 and 4 together with the tap stop rotating, and coupling half 5, having disengaged from coupling halves 2 and 4 and continuing to rotate, begins to slip (click). Tap out of the tapped hole unscrew the reverse rotation of the spindle of the machine tool. Ring 1 holds the tap in the chuck.
Reversible chucks are used when tapping threads on a drilling machine, which does not have reverse rotation (device for switching to reverse spindle rotation). They are used to unscrew the taps from the tapped hole.
For reamers, which are fixed in the spindle of the drilling machine, rocking mandrels are used to allow the tool to occupy the position coinciding with the axis of the machined hole.
It is recommended to remove cutting tools, adapter sleeves and drilling chucks from the hole of the machine spindle with the help of special wedges (fig. 6.13) or an eccentric wrench (fig. 6.14).
For the proper installation and fixation of workpieces on the table of the drilling machine various appliances are used, of which the most common are mechanical vice (screw, eccentric and pneumatic), prisms, stops, squares, conductors, special devices, etc.
Screw machine vise is widely used in single piece production, and pneumatic vise is used most often in serial and mass production when working on different groups of machines.
Quick-acting machine vise with lever-jaw clamping (fig. 6.15) are used when working on drilling machines. They ensure fast clamping of workpieces. On the flat guides of the rotary part 2 the base 9 of the movable jaw 5. The distance between the jaws of the vise depending on the size of the workpiece is adjusted by the set screw 4 with a trapezoidal thread. Jaw 5 is made in the form of a lever, at the end of which acts double cam 8 of eccentric shaft 7, moved by crank 6. Base 9 is a support for the jaws 5 of the lever and cam 8. To clamp the workpiece to be machined the handle 6 must be moved to the horizontal position.
To fix workpieces and ensure the correct position of the tool relative to the axis of the hole being drilled, special appliances. conductors. are used on drilling machines.
To guide the cutting tool in the conductor housing, there are conductor bushings that ensure precise machining of holes in accordance with the drawing. The design and dimensions of these bushings are standardized. There are permanent (fig. 6.16, a) bushes (used in conductors for small series production in processing of a hole with one tool) and quickly replaceable (fig. 6.16, b) with a lock (for the conductors of mass and large-scale production). The bushings are made from U10A or 20X steel and are heat-treated to give them the necessary hardness.
To reduce sleeve wear and offset of the machined hole axis due to possible misalignment of the tool in the sleeve, a gap is left between its lower end and the surface of the workpiece. As a result swarf does not pass through the bush and is ejected to the side. When drilling cast iron set backlash 0,3. 0,5d where d is the diameter of the bushing hole.
When drilling steel and ductile materials (copper, aluminum and other alloys) the clearance is increased (up to the diameter of the hole in the bushing).
Conductor plates are used for installation of conductor bushings in their holes. Depending on how they are connected to the conductor body, conductor plates are subdivided into permanent, rotatable, removable, suspended and liftable. Permanent plates are made as one piece with the conductor housing or are rigidly connected to it by welding or screws. Pivotable plates rotate on an axis relative to the conductor body when inserting and removing the workpiece to be machined. Removable plates are manufactured separately from the body.
Suspension conductor plates are installed on the lower ends of two guide rods and secured with nuts. The upper ends of the rods fit loosely into the holes of the sleeves pressed into the holes of the multi-spindle drill head body that is attached to the machine’s spindle sleeve. Liftable conductor plates have two holes around the edge, which are used when mounting them to the upper ends of the two wire rope guides. The installed plates are secured with nuts. The lower ends of the guide plates are inserted into the holes of the conductor body. The guide rails with faceplate are raised and lowered with a pneumatic actuator.
Use of conductors eliminates the need for marking, alignment of holes, alignment of workpieces during mounting and other operations related to drilling, reduces worker fatigue, etc.д. Therefore they are widely used in series and mass production. Depending on design, a distinction is made between overlapping, sliding, tilting and swiveling conductors.
As an example, consider overlapping conductors, which are so called because they are superimposed on the workpiece to be machined. There are two types of overhead conductors: fixed and loose. Fig. 6.17 shows a diagram of a loose overhead conductor for drilling four holes 6. The workpiece to be machined is placed by the base surface on the surface of the fixture 5 in such a way that the axes of the holes to be drilled are positioned vertically in correspondence to the direction of the working feed of the drill bit. After fixing in this position the conductor plate 4 is put on the workpiece. Two locating pins 1 and 2 ensure that the guide sleeves 3 are positioned correctly in relation to the hole axes.
Rotary and mobile devices used on drilling machines include normalized stands, rotary and mobile tables, usually used for hole machining along with removable working devices. rotary conductors for installing and securing the workpiece to be machined and guiding the cutting tool. Turning attachments having horizontal axis of rotation of the dividing faceplate are commonly referred to as rotary stands, and attachments with vertical axis of rotation are called rotary tables.
Universal assembly fixtures (USF) are widely used in many factories and are used for fixing workpieces during their processing on various metal-cutting machines (for example, for processing of holes on drilling machines). The use of the UAS provides great savings in time and money.
Multi-spindle drilling heads are an additional attachment to the drilling machine. These heads enable simultaneous machining of several holes with different tools, which significantly increases productivity of drilling machines.
Fig. 6.18 shows the design of a six-spindle turret for sequential machining of parts with different cutting tools. The head is fitted with interchangeable spindles, the drives of which have different gear ratios. Such design of the head allows without stopping and readjustment of the vertical drilling machine if the spindles are turned consecutively to perform various types of hole processing: drilling, countersinking, reaming, thread cutting and face tapping.
Each head spindle rotates to a vertical position for subsequent hole treatment with the appropriate cutting tool, automatically, without stopping the machine or changing speeds. To activate another spindle with a tool the turret mounted on the machine quill is lifted.
When working on drilling machines, the driller often uses a measuring tool to check hole diameters and depths, as well as other dimensions of workpieces to be machined.
Hole sizes are measured and checked with various measuring tools, which are selected according to the required accuracy of the measured size and the nature of production. The most common measuring tools used by the borer are: measuring ruler, protractor, squares, calipers, smooth and threaded gauges, caliper. Let’s look at some of them.
The straightedge is a rigid steel tape with the length from 150 to 1000 mm and more with the marks put on it through 1 mm and is used for approximate measurement of the overall dimensions of workpieces, the distance between the centers of holes, hole diameters, etc.д. The accuracy of measurement with a straightedge. 0,5 mm.
The indicator protractor tape gauge (Fig. 6.19, a) are used to measure precise bores of 6 mm and more in diameter. error of indications of the calipers ± 0.15 mm; division value 0.01 mm. The calipers include a set of interchangeable inserts which can be used to set the desired measurement limits.
For inspection of precise bores micrometer calipers with division value of 0,01 mm and error of indication ± 0,006 mm are used (pic. 6.19, б).
Smooth gauges. scale-free measuring tools. are used mainly in batch or mass production to check the correctness of the production of holes.
Nowadays, mainly limit bilateral gauges are used, in which one side has the largest limiting dimensions of the part and is called through (PR), and the other side has the smallest limiting dimensions and is called non-through (NOT). The ultimate smooth gauges include smooth plugs (Fig. 6.20, а).
Items with internal threads are controlled with thread gauges. prototypes of mating products. Internal thread checking gauges are threaded plugs. straight-through PR and nonthreaded NOT (Fig. 6.20, б).