Manual and mechanized drilling
Drilling is done mainly on drilling machines. In cases where the part cannot be mounted on the machine or when the holes are located in inaccessible places, drilling is carried out with the help of ratchets, ratchets, hand drilling machines, electric and pneumatic hand drilling machines.
The ratchet is used for manual drilling of large diameter holes up to 30 mm, as well as when processing parts in awkward locations where it is impossible to use a drilling machine, electric or pneumatic drilling machine.
Hand drill is used for drilling holes up to 10 mm in diameter. Drilling with a hand-held drill is carried out on low and high supports, as well as with workpieces clamped in a vice.
Manual electrical drilling machines are used for installation, assembly and repair work for drilling and reaming holes. They come in:
Electric hand drilling machines, regardless of type and power, consist of three main parts: an electric motor with an operating voltage of 220 or 36 V, a gear train and a spindle.
Countersinking is the process of machining with countersinks of cylindrical and conical rough holes in parts obtained by casting, forging or stamping, or pre-drilled in order to increase the diameter, improve their surface quality, improve accuracy (reducing taper, ovality, breakdown).
Countersinking is either the final treatment of the hole, or an intermediate operation before reaming the hole, so when countersinking leaves a small allowance for finishing the hole with a reamer (just as after drilling leave allowance for countersinking).
Countersinking provides a hole machining accuracy of up to 8. 13th quality class, roughness of the machined surface within 4. grade 6.
Countersinking. is more productive operation than drilling, because at equal (approximately) cutting speeds the feed during countersinking is permitted in 2,5 %. 3 times higher than for drilling.
The tool for countersinking is a countersink (Fig. 19), which, like a drill, is fixed in the conical hole of the machine tool spindle, and works in the same way as a drill, making rotary movement around the axis, and translational movement of the drill. along the hole axis.
A full countersink looks like a drill and consists of the same basic elements, but has more cutting edges (3. 4) и. helical grooves.
Three or four cutting edges better center the tool in the hole, giving it greater rigidity, thus ensuring high accuracy.
Figure 19. Countersink: 1. working part, 2. cutting part, 3. guide part, 4. neck, 5. shank, 6. foot
While countersinking, chips are removed by strong compressed air or water jet, or by inverting the part if it is not heavy. When countersinking parts made of steel, copper, brass, duralumin use cooling with soap emulsion.
In order to obtain a correct and clean hole, the allowance for countersinking must be: for countersinks up to 25 mm in diameter. 1 mm, for countersinks with diameters from 26 to 35 mm. 1,5 mm, for countersinking with diameters from 35 to 45 mm. countersinks up to 25 mm in diameter 2 mm.
Countersinking. is the process of working with special tools of cylindrical or conical recesses and chamfers of drilled holes for the heads of bolts, screws and rivets.
The main feature of countersinks (Fig. 20) in comparison with countersinks is the presence of teeth on the face and guide pins, by which countersinks are introduced into a drilled hole.
Figure 20. Countersinking: a. with a constant guideway and a cylindrical shank, b. with a replaceable guide and a tapered shank, in. countersinking angles, d. Tapered countersinks,
Counterbore reaming. Reaming. is the process of finishing holes, which ensures the accuracy of 7. 9 grade and surface roughness of 7. grade 8. Reaming tool. reaming.
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Holes are reamed on drilling machines and lathes or manually. Reamers used for manual reaming are called manual, and for machine reaming. by machine. Machine reamers have a shorter working part.
Hand-operated cylindrical reamers are used for reaming holes of diameter from 3 to 60 mm. They are divided into numbers 1, 2 and 3 according to the degree of accuracy.
Figure 21. Reamers: a. manual, b. machine, c. tapered
The most common connections between machine parts are threaded connections. The widespread use of threaded connections in machines, mechanisms is explained by the simplicity and reliability of this type of fastening, the convenience of tightening adjustment, and the possibility of disassembly and re-assembly without replacing the part.
Thread-cutting is the formation of threads by removing chips (and also by plastic deformation) on the outer or inner surfaces of workpieces.
there are two kinds of threads: external and internal. A rod with an outside thread is called a screw (figure 23, a), a part with an inside thread. Nut (Figure 23, b).
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These types of threads are made on machines and by hand. The production of threads by hand is considered below.
Figure 23. Parts with threads: a. external (bolt), b. internal (nut)
Depending on the direction of the coils lift on the cylindrical surface, the screw line for trimmer (thread) can be right and left. Right-hand threads are more commonly used in mechanical engineering.
Manual and mechanized drilling
Manual and mechanized drilling
Drilling is carried out mainly on drilling machines. In cases where the part cannot be mounted on the machine or when the holes are in hard-to-reach places, drilling is carried out with ratchets, ratchets, hand-held drilling machines, electrical and pneumatic hand-held drilling machines.
The ratchet is used for manual drilling of large diameter holes up to 30 mm, as well as when processing parts in awkward locations where it is impossible to use a drilling machine, an electric drilling machine or a pneumatic drilling machine.
The ratchet has a spindle that fits into the fork of the crank. On one end of the spindle, there is a hole to hold the drill bit and on the other end, a rectangular thread is threaded onto which a long nut that ends in the center is screwed. To drill with a ratchet use a clamp that allows you to set the ratchet in a certain position. Rotary motion is produced by a ratchet wheel that is securely fastened to the spindle. The dog when you turn the crank to a small speed, and when you connect the gearwheel and rotate the crank, the spindle will have a different speed, so this drill is called a two-speed. Drilling with a hand-held drill is carried out on low and high stands, and with workpieces clamped in a vice. The way you hold the drill is different.
Drilling with the low stand requires considerably less pressure on the drill than with the high stand, 6-10 mm in diameter. When drilling with a low stand, hold the drill with the right hand on the rotary knob and the left hand on the stationary knob, while you rest your chest on the bib. The handle is rotated smoothly, without jerks. The drill is held strictly vertically, without swinging, otherwise the drill could break.
Drilling on the high stand with 2. 4 mm diameter holes is usually performed on the workbench and unlike drilling on the low stand, the drill is not pressed on the chest, but with the left hand, which is taken by the bib and the right hand by the rotation knob. Test-drilling is carried out by lightly pressing on the bib. If the hole is correctly positioned, increase the pressure on the bib with the left hand and continue drilling until the end. Do not jiggle the tool in order to avoid breaking the drill bits.
alternately turning the crank by 1/3-1/4 turns to one side and vice versa to the other to make the spindle rotate in one direction only. The drill handle is long enough (300. 400 mm) to make the traction force significantly easier. The feed rate per drillstring revolution is 0.1 mm.
Hand-held drill is used for drilling holes up to 10 mm in diameter. The spindle is fitted with a bevel gear that can be coupled with the bevel wheel. In this case, when rotating the shaft with the crank, the spindle receives one
Drilling workpieces clamped vertically in a vice (fig. 3, c), is very difficult, especially at the beginning of the work. the drill comes out of the core cavity at the slightest loosening of pressure or misalignment of the drill. The part is clamped in a vice so that the borders of the hole are higher than the jaws of the vice by more than half the diameter of the chuck. Hold the drill horizontally with the left hand on the stationary crank and with the right hand on the rotation crank, drill a pilot hole by smoothly turning the crank. When the drill comes out, loosen the pressure and reduce the speed.
Electric hand-held drilling machines are used for installation, assembly and repair work for drilling and reaming holes. They are available:
chuck. The electric hand-held drilling machine is held during operation by the handles rigidly connected to the housing with both hands, and is positioned so that the center of the drill coincides exactly with the planned center of the future hole; then the special stop located on top of the housing is pressed and the electric motor is started by a button placed in the handle.
Drilling machines are made of two types:. straight. with the spindle axis positioned coaxially or parallel to the motor axis;. angular. with the spindle axis positioned at an angle to the motor axis.
According to the direction of rotation, the machines are manufactured as single-acting and reversible.
Angular machines are used for drilling in hard-to-reach places.
Manual electrical drilling machines, regardless of type and capacity consist of three main parts: an electric motor with operating voltage of 220 or 36 V, gear drive and spindle.
Of the light-duty type, the most common is the I-90 drilling machine (Fig. 4, а).
Electric motor is a universal collector type, works on alternating or direct current of 220 V voltage of standard frequency; middle type (pic. 4, 6), usually having one closed handle on the back of the housing; used for drilling holes up to 15 mm in diameter; the heavy type usually having two handles on the housing or two handles and a chest stop. Such machines are used for drilling holes up to 20-30 mm in diameter in steel parts.
Precautions at work with hand-held electrical machines:. Work only with rubber gloves and soles;. If soles are absent, rubber mat should be put under the feet. The housing of an electric hand held drilling machine must be earthed. Check that the spark plugs are properly ground (no sparks during normal operation);.if the machine stops and sparks or smells, do not disassemble the machine on site but replace it with a new one from the tool room.
Manual drilling of metal
Manual metal drilling
Manual drilling is carried out with a manual drill, ratchet, as well as with mechanized tools. pneumatic and electric drills.
Hand drill. For manual drilling a manual drill bit clamped in the drill chuck, left hand grasp the stationary handle, and the right. the movable, resting his chest in the bib, begin to rotate the drill handle with his right hand. In this process a rotary motion is transmitted to the drill bit by means of a gearbox. When drilling, it must be ensured that the drill bit is guided exactly along the axis of the hole.
Ratchet. This tool is used only when it is impossible to use any drilling machine or an electric drill to make a hole (e.g. on-site drilling of large holes during machine assembly). The ratchet has a drill chuck mounted on a spindle with a ratchet wheel; the other end of the spindle fits into a long nut with a hardened steel center. Knob with ratchet handle is attached to the spindle. By moving the handle to one side, force the dog against the ratchet tooth, turning.the ratchet wheel and simultaneously rotate the spindle with the drill. When the crank is turned in the opposite direction, the dog slides on the teeth of the ratchet wheel and the spindle does not rotate. The first of the movements is working, the second is idle.
No need to hold the ratchet in the hand when drilling: it can be clamped to the workpiece with clips. When drilling, place the center of the nut in the bracket and move the spindle with the crank. As the drill gets deeper into the hole, turn the nut to feed the drill.
Electric drill. Electric drills are widespread in the locksmith’s trade and vary greatly in design. Drills are divided into heavy, medium and light according to the nature of the work, but medium and light drills are used more often.
The entire drill mechanism is enclosed in a protective housing. Electric motor rotor shaft is made together with gear wheel, which is coupled with another gear wheel, located on intermediate shaft; the latter transmits the rotation to the spindle. Chuck fixed to the spindle in which cutting tool is inserted (drill bits, countersinks, reamers, etc. can be inserted).).
The drill motor is supplied with current from the mains through a special flexible hose carrying the electric lead.
Extreme care is necessary with electric drills, because electric shock can occur if the insulation insulation fails. The body of the core drill should therefore be firmly earthed during operation.
Pneumatic drill. Pneumatic drills are powered by compressed air supplied to the drill motor from a mains supply or from a compressor through a rubber hose at 5 bar pressure. They come in piston and rotary. Air drills use a lot of compressed air, but weigh less than electric drills. Drill SD-8, weighing only 1.5 kg, makes 2000 rpm and drills holes up to 6 mm in diameter.
Air drills are safer, therefore they are more widely used in factories than electric ones. Pneumatic drills favorably with the fact that they are not afraid of overload, causing electric drills heating and burnout of the motor windings.
Accessories for electric and pneumatic drills. The use of a variety of attachments expands the use of electric and pneumatic drills. For example, to drill holes in hard-to-reach places use a variety of extensions that are attached to the flexible shaft instead of the chuck. The drill bit is inserted into a sleeve at the free end of the bit.
Use angled attachments for drilling at an angle.
When drilling with a pneumatic drill, air must be blown through (via the air supply tap) before a hose is connected to the drill. To remove water that enters the hose and piping with the air and condenses on the walls of the air system units.
When drilling with an electric drill, you must not start without checking that the tool is in good working order. when you receive the drill from the stockroom, make sure that the drive and the plug are in good condition and check that the ground wire is connected from the center pin of the plug to the body of the drill.
How to Properly Drill Metal
The sharpness of the drill bit is essential for drilling through metal. The bluntness of the cutting edges depends on the hardness of the material being cut, the feed force, the speed of rotation, the availability of cooling and other factors. The technology of drilling large holes in metal is that first you drill with a small drill, and then use the main.
To drill accurately, it is mandatory to core the centers of the future areas to be machined. It is possible to improve the conditions of the process by dipping the tip of the tool in machine oil beforehand. At home, normal soapy water is used. The deep-hole drilling process requires constant cooling of the power tool and timely removal of accumulated metal chips.
When working with metal products of sheet type it is necessary to put a wooden bar under the place of cutting, which will prevent the appearance of burrs. Any material that is less hard than the base material can be used as a substitute for the stone. In the final step, it is recommended that the feed pressure be reduced so that dangerous burrs do not form.
Holes in pipes
The main problem of pipe drilling is their exact positioning. Often the entry point to be drilled is not the same as the exit point. Increase of pipe diameter leads to even bigger error. by eye to maintain strict perpendicularity is almost unreal, so special purchased or homemade guides and adapters are used.
Work on stainless steel at minimum rpm, preferably with a cobalt bit. 120-150 RPM will give the required cut quality and speed. If there is no speed regulator, the drill can be switched on for a short time, which prevents the chuck from reaching its maximum speed. Stepped drills can be used, making the process much easier. For diameters larger than 15 mm, special “core bits” are used. The working element is cooled by grease or olive oil.
The difficulty in working with aluminum products is the material enveloping the cutting edges. It makes it much more difficult to penetrate into the drills and simultaneously expands the place of treatment. For an accurate countersinking, more frequent removal of the drill bit from the workpiece for cleaning and use of coolant.
Countersinking is the finishing of cylindrical or cone-shaped holes, which are used to form countersinks for recessed fastener heads. This is done with a special tool called “countersinking”.
There are a number of rules that must be observed during countersinking:
- Counterbore only after the hole is completely drilled.
- Drilling and countersinking are performed in one approach. Countersinking must be carried out after drilling is completed, without removing the part from the machine mounts. In one “approach”, two tools are used.
- Only low spindle speeds (max. 100 rpm) can be used, and emulsion must be used at the same time. You can check the depth with an ordinary caliper.
- If you use a countersink with a cylindrical countersink, which has a trunnion that is larger than the size of the hole to be countersinked, you must do the following. First you drill a hole that is the same size as the trunnion. Then it is countersinked, and after all of this, drilling to the desired size is made.
Drilling metals with a machine tool and drill
Hello readers of the blog. Metal drilling is just as dangerous as metal cutting, and there are some secrets and subtleties here, too. This is what I decided to write about today.
Getting Ready to Go
Pay attention to your clothing first. If you are working in a gown, the sleeves of which do not have buttoned cuffs, put on sleeves, and on the head. a beret (or tie it with a kerchief). Do not forget safety glasses and safety shoes.
Now you can prepare the workplace. Check that your equipment is in good working order before you start drilling. This is checked at idle speed. If no problems are found at this stage, lubricate all mechanisms of the machine and close the lubrication holes.
The table is wiped with a rag and immediately removed from the working area (especially from rotating elements).
Important: Drive belts must be covered and the machine must be grounded.
The safety of drilling machines depends on the order of the workplace. Remove chips from the machine promptly, and place workpieces in the place provided for that purpose.
If there is no hole in the center of the table, have some pads on which to place the workpiece. That way you do not damage the machine when drilling through holes.
Choice of Spiral Drill Bit
When drilling metal, we use spiral drill bits with individually ground cutting edges most often. And here it is important to observe safety precautions when drilling certain parts and workpieces.
It would be better if you always had a set of twist drill bits for both wood and metal, of different diameters and lengths on hand.
I recently bought myself such a set of drills for metal and wood. Not much, but it is enough for my needs. And it costs very little.
Put a twist drill of the right diameter and length into the chuck of your drill press or power drill.
At the moment of attaching the drill, make sure that the drill is mounted clearly vertically, without any misalignment.
Attention: Before drilling, make a brief start of the drilling machine or the electric drill, and thus make sure that there are no defects and distortions in the drill. Otherwise, be sure to replace the defective drill bit.
When using small-diameter twist drill bits (3 mm), some problems may arise with their even clamping in the chuck of the drill press or power drill.To hold the drill firmly, wrap 2-3 layers of thin copper or brass wire around the drill bit shank. This trick will allow you to increase the diameter of the shank and securely clamp the drill in a standard conventional chuck. Care must also be taken with fine drill bits because they are extremely brittle.
When marking out workpieces it is necessary to establish the exact position of the center and the required dimensions of the hole. This can be determined by using a spotter’s square, a caliper or a standard ruler. To make the markings more visible, use a marker or permanent ink. The marking is in the drill area and no marks are left. It is best to mark the center of the marked hole with a punch before drilling. This reduces the risk of the drill bit slipping to the side.
After marking, before drilling the metal workpiece, it is necessary to fix it in a regular bench vice, or in the vise of the drilling machine.
Caution: When clamping chrome-plated or polished workpieces, place pads of wood, thick cloth or leather under the jaws of the vice. This will protect the surface of the workpiece.
When fixing the workpiece in the vise of the drilling machine, the machine plate should be raised, thereby reducing the distance from the workpiece to the drill bit to 2-3 cm. Do not forget to fix the fixing screws of the drill plate height adjustment. Otherwise the plate may sink during drilling. Which will cause the twist drill bit to break, spoil the workpiece, and even cause injury.
Drilling the workpiece
Operate the levers placed on the body of the drilling machine to bring the drill evenly to the workpiece.
Important: During drilling, do not apply excessive pressure to the lever that lowers the drill bit. That does not speed up the drilling process. Not only that, it will lead to overheating and then to drill bit breakage.
Some machines are equipped with a liquid / oil supply to the drill bit to avoid overheating and breakage of the drill bit, and also to avoid fusing of the edges of the workpiece (if it is plastic). Then make sure that the drill bit / drilling point is correctly fed.
In any case, even if the machine is not equipped with an automatic fluid supply system, it is not superfluous to cool the drill bit, also when working with a manual drill. It can be done by periodically either pouring water from a bottle or by dipping the tip of the drill bit into a container of water.
The marking you have made with the core cutter should coincide with the cutting edge of the lowered twist drill. Make sure no part of your clothing can get caught in the spinning parts of the drilling machine and only then start the machine.
The button for turning off the machine should be in an easily reachable and convenient place. Do not operate the machine if the on/off button is difficult to reach. This is the first safety rule for all machines.
When drilling in particular metal workpieces safety precautions should not be forgotten. Never operate the machine without first lowering the protective screen. This will keep fine metal filings out of your eyes.
When drilling with an electric or pneumatic drill, do not try to give the drill the maximum number of revolutions. When drilling deep enough holes, often lift the drill bit to get the chips out. This will extend the life of the twist drill bit, and produce a better looking hole. And again, safety precautions must be taken to avoid accidents.
This concludes the article. And the next step is threading.
Hole machining for tapered holes
With the help of reaming operation can be processed and conical holes, which previously had a cylindrical shape or were drilled with ledges, which used drills with different diameters. Making a pre-hole with ledges in such cases allows you to leave less allowance for further reaming.
Working out conical bores is pretty much the same as working out cylindrical bores. The roughing, intermediate and finishing tools are, as a rule, used for this kind of technological operation.
Sequence of tapered holes machining
A special tapered Caliber is used to check the results of such deployment. Check both the plane of contact of the surfaces of the formed hole and the gauge, and the depth of the instrument penetration.
Tapered Center Hole Calibre (TCCC)
This check is carried out as follows.
- Several pencil lines (usually 3-4) are drawn on the lateral surface of the tapered millimeter along its axis, with the lines being approximately equidistant from each other.
- Using light pressure, the Caliber is inserted into a tapered hole in the workpiece.
- Then rotate the gauge by 1/3 of a turn.
- Remove the caliber and check the condition of pencil lines on its surface.
That the reaming operation was performed qualitatively is evidenced by uniform erasure of pencil lines on all areas of the lateral surface of the gauge.
Manual electrical drilling machines are used for drilling and reaming holes for assembly, mounting and repair work. They are made of light, medium and heavy types for drilling holes in steel parts with diameter up to 9, 15 and 30 mm respectively (fig. 3.99, 3.100). Spindle axis may be direct or angular in relation to the electric motor axis. Angular machines are used for drilling in hard-to-reach places.
Regardless of their type and power, electric drilling machines consist of three main parts: an electric motor with an operating voltage of 36 or 220 V, a gearbox and a spindle.
Manual pneumatic drilling machines have smaller dimensions and less weight in comparison with electrical machines with the same power. Machine drive. pneumatic motor is operated by compressed air network with pressure of 0.5 MPa (5 kg/cm). The other elements of a pneumatic drilling machine do not differ from an electric drilling machine (Fig. 3.101). The machine drive allows smooth adjustment of the rotational speed by changing the trigger force. In case of overload the machine stops to prevent drill breakage. Overloaded electric machines have a risk of burnout of the motor winding.
Pneumatic machines have different motor power (300-1800 W) and speeds within the range of 5 to 33 seconds.1. Heavy duty machines are designed to drill holes up to 32 mm in diameter. Manual drilling machines can be used to set up drilling rigs. According to the safety requirements, electrical and pneumatic drilling machines weighing more than 6.5 kg must be suspended on a spring, rope with a counterweight or other device to relieve the driller’s hands of the drilling machine weight.
Methods of spot-welding drilling
This procedure is particularly in demand at vehicle service stations, where they perform auto body repair.
Drill bits for spot welding are the most effective and accurate way to disconnect elements. The work is performed at low speed. Otherwise, the drill will quickly overheat, which will reduce the sharpness of the cutting edges.
tool diameter does not exceed 9 mm. From the classic design drill bits are distinguished by special protrusions, which are sharpened under the cone. This allows for a 90º angle while drilling the part. Thus, there is no need to perform alignment.
Some craftsmen prefer to use cutters. They explain their choice by the fact that the tip of the drill bit cuts through the hardened part of the spot welding worse.
It is noteworthy that regardless of the type of cutting tool, it is made of one type of steel. high-speed P 18. Alloy 45X is used to produce budget models.
Drilling holes in metal. quite a complex procedure that does not tolerate violations of technological requirements. The mode of operation depends on the diameter and type of hole. Do you think it is possible to qualitatively perform the work with a hand tool without any auxiliary devices? Write your opinion in the Комментарии и мнения владельцев block.