>>Technology: Cutting metal with a hacksaw
Billets from long products are cut with a hacksaw (Fig. 67). The main parts of the hacksaw are the one-piece frame 2 (it can also be detachable, as in Fig. 68), the hacksaw blade 4 and the shank with handle 6.
A hacksaw blade is a thin strip of tool steel with two holes at the ends. On one or two edges of the blade, teeth are cut that are inclined in one direction. The hacksaw blade is attached to the frame with pins 7 and tensioned with a tension nut 1. In this case, the teeth should be directed in the direction opposite to the handle. The tension on the hacksaw blade should not be very strong or very weak, as this may cause it to break.
♦ Handsaw, frame, hacksaw blade, shank, mechanical hacksaw.
1. What is the difference between sawing with a carpenter's hacksaw and cutting with a bench saw? What are their similarities?
2. List the safety rules when working with a hacksaw.
3. What are the main parts of a hacksaw?
4. For what purpose is a cut made on the workpiece at the cutting site with a triangular file?
5. Why do you need to release the pressure on the hacksaw at the end of cutting the workpiece?
6. How to cut a long piece?
Simonenko V.D., Samorodsky P.S., Tishchenko A.T., Technology 6th grade
Submitted by readers from the website
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for a year methodological recommendations of the discussion program Integrated Lessons1. Before starting work, you must check the correct installation and tension of the blade.
2. Marking of the cutting line must be done along the entire perimeter of the rod (strip, part) with an allowance for subsequent processing of 1... 2 mm.
3. The workpiece should be firmly secured in a vice.
4. Strip and corner material should be cut along the widest part.
5. If the length of the cut on a part exceeds the size from the blade to the frame of the hacksaw machine, cutting must be done with a blade fixed perpendicular to the plane of the hacksaw machine (a hacksaw with a rotated blade).
6. Sheet material should be cut directly with a hacksaw if its thickness is greater than the distance between the three teeth of the hacksaw blade. More thin material To cut, you need to clamp it in a vice between wooden blocks and cut along with them.
7. Gas or water pipe must be cut, securing it in a pipe clamp. When cutting, thin-walled pipes should be secured in a vice using profile wooden spacers.
8. When cutting, the following requirements must be observed:
At the beginning of cutting, tilt the hacksaw away from you by 10... 15°;
When cutting, keep the hacksaw blade in a horizontal position;
In work, use at least three quarters of the length of the hacksaw blade;
Make working movements smoothly, without jerking, approximately 40...50 double strokes per minute;
At the end of cutting, release the pressure on the hacksaw and support the cut part with your hand.
9. When checking the size of the cut part according to the drawing, the deviation of the cut from the marking line should not exceed 1 mm in the larger direction.
Labor safety rules
1. It is forbidden to cut with the blade tensioned too loosely or too tightly, as this can lead to blade breakage and injury to your hands.
2. To avoid breaking the blade and injuring your hands when cutting, do not press the hacksaw down too hard.
4. When assembling a hacksaw machine, you should use pins that fit tightly into the holes in the heads without wobbling.
5. If the teeth of the hacksaw blade crumble, stop work and replace the blade with a new one.
6. To avoid the handle coming off and injuring your hands during the working movement of the hacksaw, do not hit the front end of the handle on the part being cut.
Basic rules for cutting sheet metal up to 0.7 mm thick with hand scissors
1. When marking the cut part, it is necessary to provide an allowance of up to 0.5 mm for subsequent processing.
2. Cutting should be done with sharpened scissors wearing gloves.
3. Place the sheet to be cut strictly perpendicular to the blades of the scissors.
4. At the end of the cut, the scissors should not be pulled back completely to avoid tearing the metal.
5. It is necessary to monitor the condition of the scissors-screw axis. If the scissors begin to “punch” the metal, you need to slightly tighten the screw.
6. When cutting material with a thickness of more than 0.5 mm (or when it is difficult to press the handles of the scissors), one of the handles must be firmly secured in a vice.
7. When cutting out a part of a curved shape, for example a circle, you must follow the following sequence of actions:
Mark the contour of the part and cut the workpiece with a straight cut with an allowance of 5... 6 mm;
Cut the part according to the markings, turning the workpiece clockwise.
8. Cutting should be done exactly along the marking line (deviations are allowed no more than 0.5 mm). The maximum amount of “overcut” in the corners should not be more than 0.5 mm.
Basic rules for cutting sheet metal and
strip material using lever shears
1. Cutting must be done with gloves to avoid cutting your hands.
2. Cutting of significant size sheet material(more than 0.5 × 0.5 m) should be done by two people (one should support the sheet and move it in the direction “away from you” along the lower knife, the other should press the scissors lever).
3. During operation, the material to be cut (sheet, strip) must be positioned strictly perpendicular to the plane of the movable knife.
4. At the end of each cut, the knives should not be brought to full compression in order to avoid “tearing” the material being cut.
5. After finishing work, you need to secure the scissor lever with a locking pin in the lower position.
Basic rules for cutting pipes with a pipe cutter
1. The cutting line should be marked with chalk along the entire perimeter of the pipe.
2. The pipe must be firmly secured in a pipe clamp or vice. The pipe must be secured in a vice using profile wooden spacers. The cutting location should be located no further than 80... 100 mm from the clamping jaws or vice.
3. During the cutting process, the following requirements must be observed:
Lubricate the cutting area;
Make sure that the pipe cutter handle is perpendicular to the pipe axis;
Carefully ensure that the cutting discs are positioned accurately, without distortion, along the cutting line;
Do not apply much force when rotating the screw of the pipe cutter handle to feed the cutting discs;
At the end of the cut, support the pipe cutter with both hands; Make sure that the cut piece of pipe does not fall on your feet.
Power tools and cutting equipment
metals
Mechanization of work when cutting materials is carried out in two ways: using a mechanized hand tools and through the use of stationary equipment.
Hand powered tools
Mechanical hacksaw(Fig. 2.62) is effective when cutting materials at the mechanic’s workplace. It consists of housing 2, which houses the electric motor. A drum 7 is installed on the motor shaft, into a spiral groove of which there is a pin 3 connected to a slider 4. A hacksaw blade 6 is mounted on the slider. When the drum rotates, the hacksaw blade receives a reciprocating motion and cuts the metal. During operation, the hacksaw is supported by bracket 5 and supported by the handle.
Manual electric vibration shears(Fig. 2.63) provide cutting of sheet steel up to 2.7 mm thick. They consist of a housing 3, in which an electric motor is mounted, and a knife head housing 2. The motor drives the eccentric roller 1 through a worm pair. The connecting rod 9 is mounted with its head on the eccentric roller 7, and the lower head is connected to the pin 8 of the upper knife lever b. The lower knife 5 is attached to the bracket 4. During operation, the connecting rod 9, performing a reciprocating movement, causes the knife lever 7 to swing with the upper knife 6, ensuring metal cutting. The gap between the knives is adjusted by moving bracket 4 in the cutter head housing. The size of this gap depends on the thickness of the material being cut.
Cutting metal with a hacksaw
TO category:
Metal cutting
Cutting metal with a hacksaw
Hand saw(saw) a tool designed for cutting thick sheets of strip, round and profile metal, as well as for cutting slots, grooves, trimming and cutting workpieces along the contour and other works. A hand hacksaw consists of a machine (frame) and a hacksaw blade. At one end of the frame there is a fixed head with a shank and a handle, and at the other end there is a movable head with a tension screw and a wing nut for tensioning the blade. The heads have slots into which the hacksaw blade is inserted and secured with pins.
Frames for hacksaws are made either solid (for a hacksaw blade of one specific length) (rarely), or sliding, allowing the fastening of hacksaw blades of different lengths.
To move the hacksaw apart, the knees are bent until the rivet comes out of the cutout and shifted. The rivet is inserted into the other cutout and the knees are straightened.
A machine with a mobile holder consists of a square with a handle on which the holder can be moved and secured in the desired position.
Rice. 1. Crank sheet shears with inclined knives
A hacksaw blade is a thin and narrow steel plate with two holes and teeth on one of the edges. The blades are made from steel grades: U10A, P9, Kh6VF, their hardness is HRC 61 -64. Depending on their purpose, hacksaw blades are divided into manual and machine. The canvas is inserted into the frame with the teeth forward.
The size (length) of a hand saw blade is determined by the distance between the centers of the pin holes. The most commonly used hacksaw blades are for hand hacksaws with length L - 250 - 300 mm, height b - 13 and 16 mm, thickness h - 0.65 and 0.8 mm.
Each tooth of the hacksaw blade is shaped like a wedge (cutter). On a tooth, as on a cutter, there is a rear angle, a, a sharpening angle (3, a front angle y and a cutting angle 5. a + p + y = 90°; a + p = 5.
The working conditions of the hacksaw blade differ from the working conditions of the cutter, so the angle values are different here. When cutting large-width metal, cuts of considerable length are obtained, in which each tooth of the blade removes comma-shaped chips. These chips must be placed in the chip space until the tip of the tooth comes out of the cut. The size of the chip space depends on the size of the clearance angle a, rake angle y and tooth pitch S.
Rice. 2. Hand hacksaw (machine): a - solid, b - sliding, c - with a mobile holder, d - hacksaw blade; 1 - wing nut, 2 - frame (machine), 3 - movable head, 4 - hacksaw blade, 5 - fixed head, 6 - shank with handle, 7 - pins, 8 - slots, 9 - tension screw, 10 - movable bracket
Depending on the hardness of the metal being cut, the rake angle of the hacksaw blade teeth can be zero, positive or negative.
The cutting performance of a hacksaw blade with a zero rake angle is lower than that of a blade with a rake angle greater than 0°.
To cut harder materials, blades with a larger tooth angle are used for cutting soft materials the sharpening angle is smaller. Blades with a large sharpening angle are more wear-resistant.
For cutting metals, they mainly use hacksaw blades with a pitch of 1.3 -1.6 mm, in which there are 17 - 20 teeth on a length of 25 mm. The thicker the workpiece being cut, the larger the teeth should be, and vice versa, the thinner the workpiece, the smaller the teeth of the hacksaw blade should be. For metals of different hardness, blades with the number of teeth are used: soft metals - 16, medium-hard hardened steel - 19, cast iron, tool steel - 22, hard, strip and angle steel - 22.
When cutting with a hand hacksaw, at least two or three teeth must be involved in the work (cutting metal at the same time). To avoid jamming (pinching) of the hacksaw blade in the metal, the teeth are set apart.
The setting of the teeth of the hacksaw blade is done so that the width of the cut made by the hacksaw is slightly larger than the thickness of the blade. This prevents the blade from jamming in the cut and greatly facilitates the work.
Rice. 3. Elements of a hacksaw blade tooth: a - hacksaw blade teeth; front angle of teeth: b - positive, c - equal to zero, d - negative; d-step
Rice. 4. Installation of the hacksaw blade: a - correct, b - incorrect, c - blade tension
Depending on the step size S, the routing is done along the blade and along the tooth.
Hacksaw blades with a tooth pitch of 0.8 mm (also allowed for a pitch of 1 mm) must have teeth set along the blade (wavy), i.e., every two adjacent teeth are bent in opposite directions by 0.25 - 0.6 mm. The setting is performed at a height of no more than twice the height of the tooth. The wiring pitch is assumed to be 8S.
A blade with a tooth pitch of more than 0.8 mm is set along the tooth (corrugated set). With this setting, with a small tooth pitch, two or three teeth are moved to the right and two or three to the left. With the middle step, one tooth is retracted to the left, the second to the right, and the third is not retracted. With a large step, one tooth is moved to the left, and the second to the right. Tooth setting is used for blades with pitches of 1.25 and 1.6 mm.
The routing of the hacksaw blade should end at a distance of no more than 30 mm from the end.
Preparing to use a hacksaw. Before working with a hacksaw (hacksaw), the material to be cut is firmly secured in a vice. The level of metal fastening in the vice must correspond to the height of the worker. Then a hacksaw blade is selected based on the hardness, shape and size of the metal being cut.
For long cuts, use hacksaw blades with a large tooth pitch, and for short cuts, use a fine tooth pitch.
The hacksaw blade is installed in the slots of the head so that the teeth are directed away from the handle and not towards the handle. In this case, first insert the end of the blade into the stationary head and fix the position with a pin, then insert the second end of the blade into the slot of the movable pin and secure it with a pin. Stretch the blade manually without much force (do not use pliers, vices, etc.) by rotating the wing nut. At the same time, for fear of tearing the blade, the hacksaw is kept away from the face.
A tightly stretched canvas with a slight misalignment and a weakly stretched one with increased pressure creates a bend in the canvas and can cause a break. The degree of tension of the canvas is checked by lightly pressing your finger on the canvas from the side: if the canvas does not bend, the tension is sufficient.
Position of the body of the worker. When cutting metal with a hand hacksaw, stand in front of the vice straight, freely and steadily, half-turn in relation to the jaws of the vice or the axis of the object being processed. The left leg is placed slightly forward, approximately along the line of the object being cut, and the body is supported on it. The feet are placed so that they form an angle of 60 - 70° with a certain distance between the heels.
Hand position (grip). The worker’s posture is considered correct if the right hand with a hacksaw mounted on the jaws of a vice (in its original position), bent at the elbow, forms a right angle (90°) between the shoulder and elbow parts of the arm (Fig. 121, a).
The handle (handle) is grabbed with the right hand so that the handle rests on the palm (Fig. 5, b). The handle is grasped with four fingers, the thumb is placed on top along the handle. The fingers of the left hand grasp the nut and the movable head of the hacksaw.
When cutting with a hacksaw, as when filing, strict coordination of efforts (balancing) must be observed, which consists of correctly increasing hand pressure. The movement of the hacksaw must be strictly horizontal. They press the machine with both hands, but make the greatest effort with their left hand, and with their right hand they mainly carry out the reciprocating movement of the hacksaw.
The cutting process consists of two steps:
– worker, when the hacksaw moves forward from the worker, and idle, when the hacksaw moves back towards the worker. At idling do not press on the hacksaw, as a result of which the teeth only slide, and during the working stroke, apply light pressure with both hands so that the hacksaw moves straight. When working with a hacksaw, you must follow the following rules: short workpieces are cut along the widest side. When cutting rolled corner, T- and channel profiles, it is better to change the position of the workpiece than to cut along the narrow side;
– the entire hacksaw blade must be involved in the work;
– work with a hacksaw slowly, smoothly, without jerking, making no more than 30-60 double strokes per minute (hard steel - 30-40, medium-hard steel - 40 - 50, soft steel - 50-60).
Rice. 5. Working position: b - right hand, c - left hand, a - body and hacksaw d - legs
At faster rates, fatigue sets in more quickly and, in addition, the blade heats up and dulls faster:
– before finishing the cut, release the pressure on the hacksaw, since with strong pressure the hacksaw blade suddenly jumps out of the cut, hitting the vice or the workpiece, which can result in injury;
– when cutting, do not allow the blade to heat up. To reduce friction of the blade against the walls in the cut, the parts are periodically lubricated with mineral oil or graphite grease, especially when cutting viscous metals;
– brass and bronze are cut only with new blades, since even slightly worn teeth do not cut, but slide;
– in case of breakage or chipping of at least one tooth, work is stopped immediately, the remains of the broken tooth are removed from the cut, the blade is replaced with a new one or two or three adjacent teeth are ground down on a machine and then work continues.
Rice. 6. Cutting with a hacksaw for deep cuts: a - without turning the blade, b - with turning the blade 90°, c - working in a closed loop, d - position of the fingers of the left hand
During the classes.
I. Organizing time.
Checking readiness for the lesson. Introducing students to the workshop.
II. Checking the completed material.
v What is the difference between sawing with a carpenter's saw and cutting with a bench saw? What are their similarities?
v List the safety rules when working with a hacksaw.
v What are the main parts of a hacksaw?
v For what purpose is a cut made on the workpiece at the cutting site with a triangular file?
v Why do you need to release the pressure on the hacksaw at the end of cutting the workpiece?
v How to cut a long piece?
III.Presentation of new material.
Chopping metals - a technological operation during which a layer of metal is removed from a workpiece using a chisel and a hammer or the workpiece is cut into pieces. The cutting is based on the action of a wedge - this is the shape of the working (cutting) part of the chisel (Fig. 1). Using chopping, uneven metal is removed (cut down) from the workpiece, hard crust, scale, and sharp edges of the part are removed, grooves and grooves are cut out, and sheet metal is cut into pieces. Chopping can be done in a vice, on a plate or on an anvil (Fig. 2).
The main working (cutting) tool for chopping is a chisel, and the impact tool is a hammer.
The chisel (Fig. 3) is made of tool carbon steel.
It consists of the following parts: shock, middle and working.
|
Rice. 4. Hammers: A- with a square striker; b- with a round striker. The striking part is made tapering upward, and its top, called the striker, is rounded; The chisel is held by the middle part during chopping; the working or cutting part is wedge-shaped. The sharpening angle of the cutting part is selected depending on the hardness of the material being processed. For the materials being processed, the following sharpening angles are recommended: for hard (hard steel, cast iron) -70°, for medium-hard materials (steel) -60°, for soft (copper, brass) -45°, for aluminum alloys - 35°. To cut out narrow grooves and grooves, use a chisel with a narrow cutting edge - a crosspiece. The same chisel can be used to remove wide layers of metal: first, grooves are cut with it, and the remaining protrusions are cut off with a wide chisel. Two types of metalworking hammers are used as impact tools for chopping metals: with a round and square striker (Fig. 4). The main characteristic of a hammer is its mass. For chopping metals, hammers weighing 200, 400 and 600 g are used. The length of the hammer handle depends on its weight and is 250...50 mm. Cutting metals is a labor-intensive operation. To make work easier and increase productivity industrial enterprises Pneumatic and electric hammers are used. |
Metal cutting techniques
To cut metal, use a strong, massive vice. The cutting is carried out at the level of the jaws of the vice or above this level according to the intended risks. Sheet and strip metal is cut at the level of the jaws of the vice; workpieces with wide surfaces are cut above the level of the jaws.
The workpiece must be secured in the vice firmly and securely. To avoid crushing the surface of the workpiece with the jaws of the vice when clamping, you can install jaws on them.
The working position should ensure the greatest stability of the body of the worker when struck with a hammer. The body must be straightened and turned half-turn (45°) to the axis of the vice, left leg is set half a step forward, and the angle formed by the lines of the axes of the feet is 60...75° (Fig. 5).
Rice. 5. Working posture when chopping. Rice. 6. Chisel position at
The chisel is taken with the left hand by the middle part at a distance of 15...20 mm from the edge of the striking part. Install the chisel so that the cutting edge is on the chip removal line (cut line), and the chisel shaft makes an angle of 30...35° to the surface being processed and approximately 45° to the jaws of the vice (Fig. 6).
The hammer is taken with the right hand by the handle at a distance of 15...20 mm from its end. Squeezing the handle tightly with all fingers, apply fairly strong blows with a hammer to the center of the chisel striker. There are blows of the hand, elbow and shoulder.
During a wrist strike (Fig. 7, a), only the wrist of the right hand bends. During the swing, slightly unclench your fingers (except for the thumb and index), then sharply squeeze your fingers and strike. They use hand blows to cut and remove a thin layer of soft metal.
With an elbow strike (Fig. 7, b) the right arm is bent at the elbow. To receive a strong blow, the arm is extended quickly. Metal is most often cut with such blows.
The shoulder blow (Fig. 7, c) involves the shoulder, forearm and hand. All this contributes to a large swing and a maximum impact.
Rice. 7. Types of milk blow when chopping: A- carpal; b - elbow;
V- shoulder.
Rice. 8. Cutting metal on a slab.
Using shoulder blows, a thick layer of metal is removed or a thick piece of durable material is cut. When chopping, the hammer blow force must correspond to the nature of the work. This takes into account the weight of the hammer and the length of its handle. The heavier the hammer and the longer the handle, the harder the blow can be. To cut strip metal at the level of the vice jaws, first mark the cut line (mark), then secure the workpiece in the vice so that the mark is at the level of the vice jaws. Having assumed the correct working position and placing the chisel with the cutting edge on the cut line, they cut the workpiece with elbow blows, finishing the cutting with wrist blows.
|G1 To ensure that the cutting line is smooth, cutting metal GI on a plate or on an anvil follow the markings, setting the chisel vertically (Fig. 8). By moving it during the cutting process, part of the blade is left in the already cut groove.
When cutting a workpiece of relatively large thickness on a slab or anvil, they first cut it on one side, then turn it over and cut along the line on the other. The workpiece, cut on both sides, is carefully broken in a vice or on the edge of the plate.
IV.Practical part.
Students are encouraged to cut metal using methods known to them.
When cutting metals, you must comply with labor safety requirements.
1. Securely secure the workpiece in the vise.
2. Work only with a serviceable tool (withoutchins, nicks, burrs, etc.).
3. Wear safety glasses when working.
4. Do not check the cutting quality by touch.
5. At the end of the cut, ease the force of the blow.
6. For removing chopped metal particles from the workeruse a broom brush.
V.Consolidation of new material.
Ø What should be the working posture and grip of the tool when chopping metals?
Ø Which blow - wrist, elbow or shoulder - creates more force? How do the length of the handle and the weight of the hammer affect the impact force? Justify your answer.
Ø How is metal chopping done in a vice?
Ø How do you cut metals on a slab or anvil?
Student self-esteem. Cleaning of workplaces and workshop premises.
Target: teach students how to use a hacksaw correctly, familiarize them with the cutting process, and cultivate accuracy in their work.
Equipment and tools: mechanic's workbench, hacksaw, long products.
During the classes
Organizing time.
Checking readiness for the lesson. Introducing students to the workshop.
Repetition of covered material.
What are the main parts of a caliper?
How many measuring scales does a caliper have?
What measurements can you take with a caliper?
How many times is the accuracy of measurement with a caliper greater than the accuracy of measurement with a ruler?
List the rules for handling vernier calipers.
How to use a caliper to count whole and tenths
fractions of a millimeter?
What feature of the vernier allows you to take measurements with an accuracy of 0.1 mm?
Presentation of new program material.
When processing rolled metal, it is often necessary to manually cut the material into pieces. Thin sheet metal is cut with scissors, strip metal, thick sheet metal, as well as rods, angles, etc. - with a hacksaw.
A hacksaw consists of two main parts: a hacksaw (frame) and a hacksaw blade. In Figure 1, A shows a bench saw with a solid hacksaw. It can hold a hacksaw blade of a certain length. In order to be able to attach hacksaw blades of different lengths to the hacksaw, the hacksaw machine is made sliding (Fig. 1, b).
The sliding machine consists of front and rear angles connected to each other by a clip. The distance between the shank and the tension screw can be changed due to the position of the rear square inserted into the cage. The deeper the square is inserted into the cage, the shorter this distance. A shank with a handle is installed in the rear square of the hacksaw machine. The shank has a slot and a hole for a pin. The front angle contains a tension screw with a wing nut. The tension screw has the same slot and the same hole as the shank. The ends of the hacksaw blade are installed in the slots of the shank and tension screw, which are secured using pins inserted into the holes. By rotating the wing nut, the hacksaw blade is tensioned.
The hacksaw blade is a thin and narrow steel plate with teeth on one of the ribs (see Fig. 1, a).
Fig.1. Hand saw: A- with a one-piece machine; b- main parts of the sliding machine.
There are holes at the ends of the hacksaw blade for securing it in the hacksaw machine. The length of the most common hacksaw blades is 250...300 mm. Each tooth is wedge-shaped and acts like a chisel when cutting. When notching, the size of the teeth is chosen so that the resulting chips are placed between the teeth before they exit the cut. To ensure that the width of the cut made with a hacksaw is slightly larger than the thickness of the blade, the teeth are set - every 2-3 adjacent teeth are slightly bent in different directions. This wiring is called corrugated.
Please note that the teeth should be directed in the direction opposite to the hand, and the tension of the blade should be such as not to cause breakage of the blade.
The workpiece is firmly secured in a vice and a cut is made with a file at the cutting site.
The cutting site is located at a distance of 10 - 15 mm from the edge of the jaws.
a b
Rice. 2. Working with a hacksaw: a - position of the body; b - hand position.
During the working stroke of the hacksaw (forward), the hacksaw is moved with light pressure, while at idle (backward) - without pressure.
If the thickness of the workpiece is 3 teeth of the blade, the workpiece is clamped between two wooden blocks.
If the workpiece is long and the frame rests on its end, then the canvas is fastened as shown in Fig. 3.
Rice. 3. Cutting with a hacksaw:
a - without turning the blade; b - with rotation of the canvas.
Preparing a hacksaw for work.
Preparing a hacksaw for work involves installing the hacksaw blade into the machine and tensioning it.
First, the front and rear angles of the machine are moved apart to the length of the hacksaw blade and the machine is secured in this position using a clamp. Then insert the ends of the hacksaw blade into the slots of the tension screw and shank and align their holes with the holes in the hacksaw blade. At the same time, make sure that the teeth of the blade are directed in the direction opposite to the handle. After this, the pins are inserted into the holes and the blade is tightened by rotating the wing nut. The tension of the canvas should not be very strong, but sufficient so that it does not bend during operation. Strong tension on the blade can lead to its breakage at the slightest misalignment during operation. If the tension of the blade is weak, it will 1 bend during operation, which can also lead to its breakage.
Cutting techniques. To cut the workpiece, it is securely secured in a vice so that the cut location is close to the edge of the jaws of the vice. In this position, the workpiece will not vibrate during cutting. At the site of the cut, a mark is marked with a file. Then they take the necessary working position: stand half-turned towards the vice (Fig. 4). The handle of the hacksaw is grasped with the fingers of the right hand: the end of the handle should rest against the middle of the palm
Fig 4. The position of the body and legs when Fig 5. Hand position when
working with a hacksaw. Working with a hacksaw.
Safety precautions when working with a hacksaw.
Use only a working hacksaw with a securely fastened and properly tensioned blade. A poorly secured or loosely tensioned blade may jump out or break during operation, which creates a hazard.
getting injured.
The handle of the hacksaw should be firmly seated and free of cracks.
You cannot secure the hacksaw blade with nails or screws instead of pins.
Do not use a hacksaw that has broken teeth in its blade.
Brush sawdust off the workbench. Do not blow or remove them with your bare hands.
Support the part of the workpiece to be cut so that it
I didn’t fall and didn’t hurt my legs.
Practical part.
Mark the template blanks.
Cut the blanks.
Check the dimensions according to the drawing.
File the ends of the workpieces.
When working, use the entire length of the blade. This ensures even tooth wear and longer blade life.
To prevent the blade from heating up during operation, lubricate it with oil.
If the cut is large enough and during normal installation of the blade the machine interferes with cutting, then the blade is rotated 90° (Fig. 3 b).
When cutting workpieces that have ribs or sharp edges, be sure to next rule: cutting should go from the plane to the edge so as not to break the teeth of the blade.
Reinforcing the material covered.
What is the difference between sawing with a hacksaw and cutting?metalworking industry? What are their similarities?
List the safety rules when working with a hacksaw.
What are the main parts of a hacksaw?
For what purpose is a cut made with a triangular file on the workpiece at the cutting site?
Why do you need to release the pressure on the hacksaw at the end of cutting the workpiece?
How to cut a long workpiece?
Final part.
Evaluate the work completed by students. Point out errors.
Cleaning of workplaces and workshop premises.