Metal Cutting With A Hacksaw For Metal
Wood and metal processing
A hand-held hacksaw (saw) is a tool designed for cutting thick sheets of strip, round and profile metal, as well as for cutting slots, groins, trimming and cutting out workpieces along the contour and other works. The hand-held locksaw 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 nut (wing) 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 in one piece (for a hacksaw blade of one specific length) (rarely). or sliding, allowing the fastening of a hacksaw blade of various lengths.
To expand the hacksaw, the knees are bent until the rivet comes out of the cutout and displaced. The rivet is inserted into the other cutout and the knees are straightened.
The machine with a movable holder consists of a square with a handle, along which the holder can be moved and fixed in the desired position.
A hacksaw blade is a thin and narrow steel plate with two holes and teeth on one of the ribs. Cloths are made of steel grades: U10A, P9, Kh6VF, their hardness HRC 61. 64. Depending on the purpose, hacksaw blades are divided into manual and machine. The blade is inserted into the frame, teeth first.
The size (length) of a hand-held hacksaw blade is determined by the distance between the centers of the pin holes. The most often used hacksaw blades for hand hacksaws with a length of L. 250. 300 mm, a height L. 13 and 16 mm, a thickness of h. 0.65 and 0.8 mm.
Each tooth of a hacksaw blade is shaped like a wedge (cutter). On the tooth, as on the incisor, the posterior angle is distinguished, and. taper angle (3, rake angle y and 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, therefore the angles are different here. When cutting metal of large width, cuts of considerable length are obtained, in which each tooth of the blade removes a chip that looks like a comma. These chips must be positioned in the chip space until the point of the tooth comes out of the cut. The size of the chip space depends on the value of the back angle a, the front angle y and the pitch S of the tooth.
Depending on the hardness of the metal being cut, the rake angle of the teeth of the hacksaw blade can be zero, positive or negative.
The cutting performance of a hacksaw blade with a zero rake angle is lower than blades with a rake angle greater than 0 °.
For cutting harder materials, blades are used, in which the angle of sharpening of the teeth is greater, for cutting soft materials, the angle of sharpening is less. Blades with a large taper angle are more wear-resistant.
For cutting metals, they use mainly 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 to be 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 hardness 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 (cut metal at the same time). To avoid jamming (pinching) 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 with the hacksaw is slightly greater than the thickness of the blade. This prevents the blade from jamming in the cut and greatly facilitates the work.
Depending on the size of the step S, the wiring is done along the blade and along the tooth.
Hacksaw blades with a pitch of 0.8 mm (also allowed for a pitch of 1 mm) must have a set of teeth along the blade (wavy), i.e. every two adjacent teeth are bent in opposite directions by 0.25. 0.6 mm. The setting is carried out at a height of no more than twice the tooth height. The routing step is assumed to be 8S.
The blade with a tooth pitch of more than 0.8 mm is spread along the tooth (corrugated divorce). With this divorce, with a small tooth pitch, two or three teeth are retracted 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, the third is not retracted. With a large step, one tooth is taken to the left, and the second to the right. Tooth setting is used for blades with a pitch of 1.25 and 1.6 mm.
The setting of the hacksaw blade should end at a distance of no more than 30 mm from the end.
Preparing to work with a hacksaw. Before working with a hacksaw (hacksaw), the material to be cut is firmly fixed in a vice. The level of metal fastening in the vice must correspond to the height of the worker. Then choose a hacksaw blade, in accordance with the hardness, shape and size of the cut metal.
For long cuts, take hacksaw blades with a coarse tooth pitch, and for short cuts, with a fine pitch.
The hacksaw blade is positioned in the slot of the head so that the teeth point away from the handle and not toward the handle. In this case, first, the end of the web is inserted into the fixed head and the position is fixed by laying the pin, then the second end of the web is inserted into the slot of the movable pin and fixed with the pin. The canvas is pulled by hand without much effort (the use of pliers, vices, etc. is prohibited) by rotating the wing nut. At the same time, for fear of rupture of the blade, the hacksaw is kept away from the face.
A tightly stretched web with a slight skew and a weakly stretched with increased pressure creates a bend in the web and can cause a break. The degree of tension of the web is checked by lightly pressing a finger on the web from the side: if the web does not bend, the tension is sufficient.
The position of the body of the worker. When cutting metal with a hand hacksaw, they stand in front of the vice straight, freely and steadily, half-turned in relation to the jaws of the vice or the axis of the workpiece. The left leg is slightly put forward, approximately along the mowing line of the object being cut, and the body is resting on it. The feet are positioned 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 installed on the jaws of the vise (in its original position), bent at the elbow, forms a right angle (90 °) between the shoulder and elbow parts of the hand (Fig. 121, a).
The handle (handle) is grasped with the right hand so that the handle rests on the palm (Fig. 5, b). The handle is wrapped with four fingers, the thumb is placed on top along the handle. Fingers of the left hand grasp the nut and the movable head of the hacksaw.
When cutting with a hacksaw, as well as when filing, strict coordination of efforts (balancing) must be observed, which consists in the correct increase in hand pressure. The movement of the hacksaw must be strictly horizontal. Press on the machine with both hands, but the greatest effort is made with the left hand, and with the right hand, the hacksaw is mainly reciprocating.
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. When idling, they do not press on the hacksaw, as a result of which the teeth only slide, and during the working stroke, light pressure is created with both hands so that the hacksaw moves in a straight line. When working with a hacksaw, the following rules must be followed: short workpieces are cut along the widest side. When cutting rolled angular, tee 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, mild steel. 50-60).
At a faster pace, fatigue is more likely to occur and, in addition, the canvas heats up and dulls faster:
– before the end of the cut, the pressure on the hacksaw is weakened, since with strong pressure the hacksaw blade jumps out of the cut, hitting a vice or part, as a result of which it can cause injury;
– do not allow the blade to heat up when cutting. To reduce the 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 immediately stopped, the remnants of the broken tooth are removed from the saw cut, the blade is replaced with a new one or two or three adjacent teeth are ground on the machine and then continue to work.
Cutting metal with a hand-held locksaw hacksaw without turning the blade
For cutting metal bars of a circular cross-section, the cutting points are marked with a scribe. The bar is clamped horizontally in a vise, pushing the cut end to the left of the vise jaws so that, when working with a hacksaw, its head does not touch the side surface of the vise. If the cutting plane is too far from the vise jaws, the bar will tremble during cutting, making cutting difficult. The bar must be securely clamped in a vice.
On the workpiece (at risk), make a small cut with a triangular file so that the hacksaw blade does not slip on the surface of the bar at the beginning of cutting. Then they take a hacksaw, take a working position, grease the canvas with boiled oil with a brush, insert the cutting edge of the hacksaw blade into the cut and start cutting (Fig. 77, a).
At the beginning of cutting, the pressure on the hacksaw blade should be less, and as the blade approaches the center of the bar, the pressure is increased.
During cutting, the hacksaw blade sometimes “pulls” to the side, this creates an oblique cut (due to weak blade tension or incorrect position of the hacksaw and its direction). If the blade is pulled to the side, it is necessary to turn the bar and start cutting g on the opposite side opposite the notch. At the end of the cut, you need to release the pressure on the hacksaw and reduce the pace of movement.
to the end using the entire length of the hacksaw blade and constantly monitoring the position of the blade and its direction in relation to the risk. At the end of the cut, the pressure is released.
Cutting strip metal (Fig. 77, c), as a rule, should be performed on the narrow side of the strip, provided that cutting is performed at least three teeth of a hacksaw blade. The fewer teeth are simultaneously involved in the work, the less pressure on the hacksaw blade.
Cutting workpieces with a thickness less than the pitch of the blade teeth should be carried out with a hacksaw in a vertical position, with weak pressure on the tool. In this case, work with a hacksaw slowly using the entire length of the hacksaw blade.
When cutting pipes, the cutting points are marked using a template. The template is made of thin sheet metal, bent around the circumference of the pipe.
The length of the segment is marked with a measuring ruler from the end of the pipe. The edge of the template is brought to the mark, applied with a scribe across the entire
For cutting, the pipe is clamped horizontally in a vice. To avoid crushing the pipe, it is clamped in spacers (Fig. 77, e). For cutting, choose a blade with fine teeth (tooth pitch 1 mm), cut with a triangular file at risk and start cutting. As the hacksaw deepens into the pipe wall, the hacksaw is slightly tilted towards you. Having cut the pipe to the wall thickness, take out the hacksaw, turn the pipe 45-60 ° away from you and continue cutting, combining the pipe rotation with cutting along the entire circumference of the pipe. The rate of movement when cutting pipes should be 35-45 strokes per minute with low pressure on the hacksaw. At the end of the cut, the pressure on the hacksaw must be released.
Before cutting the corner, it is marked on the planes of the shelves. The angle shelf must be installed in a vice (Fig. 77, d). The angle must be cut along the narrow edge of the flange where less cutting force is required. Therefore, cutting will be much easier.
Having cut the first shelf to the inner plane of the second shelf, the corner is set to the cutting position of the first shelf, continuing cutting to the end. At the end of the cut, release the pressure on the hacksaw.
The correctness of the cut is checked with a ruler, and the angle is 90 °. square.
Cutting metal with a hacksaw
Work with a hand-held locksaw
The work is performed in the following sequence:
The blade is inspected, paying attention to the absence of cracks, bends, as well as to the set of teeth.
The serviceability of the frame (body) of the hacksaw is checked: the tightness of the handle, the free rotation of the wing nut, the movement of the sliding part and the tension pin, the presence of pins. Install the sliding part of the hacksaw according to the size of the blade, leaving the extended pin for tension by 10-12 mm. Install the blade in the slots of the heads so that the teeth are directed away from the handle (Fig. 74). In this case, the end of the web is first inserted into the fixed head until the holes coincide and the position is fixed by laying the pin. Then insert the second end of the blade into the slot of the movable pin and fix it with a pin. Tighten the blade, screw the wing nut without much effort, without resorting to pliers, vices and other tools
When cutting with a hacksaw, stand in a vise straight, free and stable, half-turned in relation to the vise jaws. The left (supporting) leg must be put slightly forward.
The instructor demonstrates the correct holding of a hand-held mechanic hacksaw in three steps; 1) the hacksaw is taken in the right hand so that the handle rests on the palm (Fig. 75, a); 2) the handle is covered with four fingers, putting the thumb on the handle from above (Fig. 75, b); 3) with the fingers of the left hand, take the front square of the hacksaw, the lamb and the tension bolt (Fig. 75, rff.
The hacksaw blade is installed on a wide plane of a wooden block, creating a slight downward slope of the front of the hacksaw at the beginning of cutting. To obtain the exact direction of cutting according to the marking, it is necessary to put the thumbnail of the left hand at the risk, press the hacksaw blade tightly against it (Fig. 76, a), and cut with the right hand (Fig. 76, b). Continuing cutting, the cutting edge of the blade is gradually transferred to a horizontal position (Fig. 76, c).
The movements when working with a hacksaw should be smooth, without jerks and with such a scale that all the teeth of the blade participate in the cutting. The pace of movement when cutting with a hacksaw should be 30-60 strokes per minute. When finishing cutting, you should loosen the pressure on the hacksaw, reduce the pace of movement in order to avoid breaking the blade and injuring your hands. After the end of the work, the hacksaw, turned with the blade to the vise, is placed on the workbench on the right side of the vise.
When cutting a metal bar with a square cross-section, first mark the cutting place, for which they measure the length of the workpiece with a measuring ruler, applying risks with a scribe. After that, using a square with a wide base, they draw risks on the upper and two sides of the square. Next, the bar is clamped in a vice so that the risk is located on top.
To preserve the teeth of the blade, cutting begins g of the rear edge of the part, tilting the hacksaw away from you until the start of the cut is formed with weak pressure (Fig. 77, b). The slope is gradually reduced until the cut reaches the leading edge and the hacksaw blade is horizontal. In this position, the pressure on the hacksaw is increased, continuing to cut the bar.
Cutting metal with a hand-held locksaw with a turn of the blade
The work is performed in the following sequence:
- The markup is done in the usual way.
- The hacksaw is prepared for work, and the quality of the blade is checked and its suitability for work.
- The blade must be installed in the side slots of the heads perpendicular to the plane of the hacksaw (the teeth are directed from the handle); then you should lay the pins in the hole and pull the canvas.
- Place the workpiece and clamp it in a vice from the side, pulling out the cut-off piece so that during vertical cutting the head of the hacksaw does not touch the side surface of the vice and does not interfere with the movement of the hands. In addition, the workpiece must rise slightly above the level of the vise jaws, otherwise the workpiece will vibrate during cutting. When cutting, it is necessary to follow the direction of the blade, keeping the plane of the hacksaw in a horizontal position.
The movement of the hacksaw should be carried out smoothly, without jerking, avoiding skewing of the blade, as this can lead to its withdrawal or breakage.
As the metal is cut, the workpiece must be moved higher to continue cutting (Fig. 78), reducing the rate of movement and the force of pressing the hacksaw at the end of the cut.
The size of the cut workpiece is checked according to the marked risks.
The essence and purpose of cutting. Hand hacksaw cutting
Cutting (cutting). an operation to separate parts from bar or sheet metal. Cutting differs from felling in that impact forces are replaced by loads. It is performed in two ways: with and without removal of chips. For cutting with removal of shavings, the following are used: hand saws, cut-off hacksaw machines, metal saws, metal-cutting machines (turning, milling, grinding), autogenous gas cutting, anode-mechanical cutting, etc. Cutting without removing shavings is carried out with manual, lever and mechanical shears, nippers, pipe cutters, press-shears, parallel (guillotine) shears, dies, etc. Cutting is hand and machine.
A hand hacksaw is used to cut sheets, strip, round and profile metal, cut grooves, trim and cut out workpieces along the contour, etc.
Hand-held locksaw (fig. 7.1) consists of a machine (frame) 5, a handle 6 and hacksaw blade 3. The canvas is inserted with its ends into the slots of the movable 2 and motionless four heads, after which they are fixed with pins and tightened with a screw with a wing nut one. Hacksaw frames are made in one piece (Fig. 7.1, a) and sliding (Fig. 7.1, b). The former are used to fix hacksaw blades of one specific length, the latter allow you to fix hacksaw blades of different lengths.
Hacksaw blade is a narrow steel hardened plate with teeth on one or two edges and two holes along the edges (Fig.7.2, and). The length of a hand hacksaw blade is equal to the distance between the centers of its two holes. According to GOST 6645-86, the following main dimensions of the hacksaw blade can be distinguished: length I, width L, height B, step R teeth. The most commonly used hacksaw blades for hand hacksaws length I, equal to 250 or 300 mm, height B, equal to 13 or 16 mm, width / r, equal to 0.65 and 0.8 mm, respectively.
Figure: 7.1. Hand locksaw hacksaws: and. efficient (one. wing nut; 2. movable head;
- 3. hacksaw blade; four. fixed head; five. frame;
- 6. handle); b. sliding
Each tooth of a hacksaw blade is wedge-shaped (fig. 7.2, b) and the following geometry: clearance angle a, taper angle (3, rake angle y, cutting angle 5. For the geometry of the hacksaw blade, the following equalities are fulfilled:
When cutting, a comma-shaped chip is placed between two adjacent teeth until the point of the tooth comes out of the cut. The size of the chip space depends on the value of the clearance angle a, the front angle y and the pitch R. For cutting metals of different hardness, the following angles are taken: y = 0.12 0. a = 35.40 °, P = 43. 60 °. For cutting harder materials, blades are used, in which the angle of sharpening P is greater, for cutting soft materials, less.
Step P teeth of a hacksaw blade. the distance between two adjacent teeth (fig. 7.2, b). The choice of a hacksaw blade with the appropriate pitch depends on the properties of the metal being cut. For cutting cast iron, mild steel, a blade with a step of 1.2 is used. 1.5 mm profiled steel
Fig. 7.2. Saw blade:
and. the device of the canvas; b. the geometry of the blade tooth; in. wiring along the canvas; r. spread on the tooth; to. cutting width
rolled products and pipes, non-ferrous metals. 1.25, thin-walled pipes, thin shaped rolled products, soft and ductile metals and alloys (brass, copper). 1.0, for sheet steel. with a pitch of 0.8 mm.
To avoid jamming the hacksaw blade in the metal, the teeth are set apart. There are two wiring methods: 1) on the canvas (wavy wiring) (fig. 7.2, in), when the web is bent to form waves in increments of 8R; 2) by the tooth (fig. 7.2, d). only the teeth are set apart in different directions and the blade is not affected. The spread on the canvas is used for canvases with a pitch of up to 0.8 mm, the spread on the tooth is used for canvases with a pitch of more than 0.8 mm.
Cloths are made of steel grades U10A, P9, Kh6VF with hardness Sh1S 61.64.
Before proceeding with metal cutting, it is necessary to choose a hacksaw blade taking into account the hardness, shape and size of the metal being cut. The blade of the hacksaw must be installed in the slots of the heads of the hacksaw so that the teeth are directed with the tip from the handle (see Fig. 7.1, and). In this case, the end of the web is first inserted into the fixed head until the holes coincide and the position is fixed by installing a pin in them. Then, the second end of the web is inserted into the slot of the movable head and fixed with a second pin. Tighten the canvas by rotating the wing nut (Fig. 7.3, and). It should be borne in mind that a tightly stretched web with a slight skew can break, and a weakly stretched one bends during the cutting process and breaks.
Fig. 7.3. Techniques for working with a hacksaw: and. tension of the hacksaw blade; b. position of the right hand; in. position of the left hand; r. plunge into rolled rectangular section; d. plunge into a round bar; e. cutting a thin sheet
Then the workpiece is marked out and securely fixed in a vice. The height of the vise should correspond to the height of the worker (Fig. 7.4, and). When cutting, it is necessary to stand half-turn to the vice, i.e.
at an angle of 45 ° to the longitudinal axis of the vise (Fig. 7.4, b). The distance between the vice and the body of the worker must be
- 200.300 mm. Stand in front of the vice must be straight, free and stable. The left leg is put forward and the body is supported on it. Place your feet so that they form an angle
- 60.70 °. The worker’s posture is considered correct if a right angle is formed between the shoulder and elbow parts of the right arm bent at the elbow with a hacksaw installed on the jaws of the vice (Figure 7.4, and).
Fig. 7.4. Position when working with a hacksaw: and. cases and hacksaws; b. legs (feet)
The hacksaw handle is wrapped with four fingers of the right hand, while the end of the handle should rest against the middle of the palm, and the thumb is placed along the handle (see Fig. 7.3, b). With the left hand, take the hacksaw frame so that the thumb is inside the frame, and the rest grab the tension screw of the movable head (see Fig. 7.3, in). To facilitate plunging, the hacksaw is tilted towards the rear edge of the workpiece (see Fig. 7.3, d) or put a metal stop at the place of the cut and abut the hacksaw blade against it (see Fig. 7.3, e). In some cases, a shallow cut is made in the place of the future cut with a triangular file for better direction of the hacksaw. When cutting, it is necessary to coordinate the efforts of the right and left hands. The movement of the hacksaw must be strictly horizontal. Press on the hacksaw with both hands, but make the greatest effort with the left hand, and with the right hand perform the reciprocating movements of the hacksaw.
The cutting process consists of two strokes: the worker, when the hacksaw moves forward from the worker, and the idle, when the hacksaw moves back towards the worker. When idling, the hacksaw is not pressed, but pulled towards you. During the working stroke, press the hacksaw with both hands, providing the cutting force.
When working with a hacksaw, the following rules must be observed:
- the whole canvas should be involved in the work;
- you should work with a hacksaw slowly, without jerks, smoothly;
- the rhythm of the hacksaw is 30.40 double strokes per minute when cutting hard steel, 40.50 when cutting medium hard steel and 50. 60 double strokes per minute for cutting mild steel and non-ferrous alloys;
- short workpieces are cut along the widest side;
- before the end of the cut, the pressure on the hacksaw is weakened, since with strong pressure the hacksaw blade can break and cause injury to the worker;
- the canvas must be periodically lubricated with mineral oil or graphite grease;
- a new blade should cut softer steels and alloys, dull ones. harder;
- pressure on the hacksaw depends on the hardness of the metal and the size of the cut part (hard metals require more pressure than soft, narrow parts. less pressure);
- the workpiece must be securely fixed in a vice;
- if the blade has “taken” away from the marking risks, you need to turn the workpiece and start cutting in a new place.
Workpieces of different profiles and sections are cut with a locksaw hacksaw. In this case, it is necessary to take into account some of the features of cutting these blanks.
- 1. Strip material is cut along a narrow plane if its thickness provides simultaneous operation of at least three teeth. Therefore, thin strip material is cut in the following ways: a) along a wide edge; b) along a narrow edge, holding the workpiece between two wooden blocks (see Fig. 7.3, e); c) along a narrow edge, collecting several identical blanks together (package). These methods of cutting narrow workpieces exclude chipping of the blade teeth.
- 2. Round, square, hexagonal rods are cut at the horizontal position of the hacksaw, but so that the blade does not meet sharp corners when moving. Such rods are usually notched on two or four sides.
- 3. When cutting wide enough surfaces, tilt the hacksaw alternately to the back and front edges of the workpiece. In this case, the cutting does not take place over the entire cutting width and the work is facilitated.
- 4. For long or deep cuts, when it is not possible to complete the cut due to the fact that the hacksaw frame rests against the end of the workpiece and interferes with further cutting (Fig. 7.5, and), it is necessary to turn the canvas in the frame by 90 ° (Fig.7.5, b).
Fig. 7.5. Cutting with a hacksaw for deep cuts: and. the frame rests against the workpiece; b. cutting with blade turns by 90 °; in. work in a closed loop
When cutting blanks with a closed rectilinear contour (Figure 7.5, c), cutting is also performed with the blade turning 90 °. Before cutting, holes are drilled in the workpiece at the intersection of future cuts with a diameter equal to the width of the blade, and, passing the blade through the holes, fix it in the frame and cut along the markings.
When cutting workpieces with a curved contour, jigsaw saws are used (Fig.7.6, and).
Fig. 7.6. Cutting techniques: and. jigsaw saw; b. cutting the pipe with a hacksaw; in. slotting
- 7. Cutting the pipe is performed according to the marking, holding it in a parallel vice. Thin-walled and cleanly machined pipes on the outer surface are cut by clamping them in a vice between two wooden blocks (Fig.7.6, b). When cutting, turn the pipe periodically. It is necessary to cut with very light pressure and at the same time do not deflect the hacksaw blade away from the marking risks. If the hacksaw “takes” away from the marking risks, then the pipe must be turned and cut in a new place.
- 8. Before proceeding with the cutting of the metal of the shaped section, for example, an angle profile, it is necessary to use a square and a scribe to apply marking marks in the cut points on both shelves (when cutting a channel, the risk should be applied to its wall as well). After that, the metal to be cut is clamped in a vice so that the risks of both shelves are visible, and a small cut is made with a triangular file along the risk from the corner of the profile base. Having installed the hacksaw blade in the cut, they begin to cut the profile, holding the hacksaw in an inclined position, and then level it and cut it in a horizontal position. When cutting blanks of different profiles with a hacksaw, it is necessary to monitor its direction all the time, not allowing to deviate from the marking risks.
A hacksaw can be used to make slots in the screw heads (fig.7.6, in). Wide slots (slots) are made with two canvases folded together.
Industrial training lesson “Cutting metal with a hacksaw
For preschoolers and pupils of grades 1-11
Record low registration fee 25 R.
Description of the presentation for individual slides:
Methodical development of a lesson in industrial training: “Cutting metal with a hacksaw” Master of industrial training Zabrodina LB.
The purpose of the lesson: Educational goal: To teach students how to cut metal, use tools and devices for cutting metal. the ability to organize your workplace to comply with the safety rules of labor practices when cutting metal. Developing: develop the technical thinking of students to master the basic concepts, knowledge and techniques when cutting metal with a hacksaw. develop the ability to anticipate possible types of marriage and ways to eliminate them; development of thinking memory when working in the form of surveys on the topic covered. Educational: To foster in students a conscious attitude to work, an understanding of the importance of the profession being studied. To foster a sense of responsibility for the task entrusted and the end result of work. To educate students to respect equipment and tools.
Objectives of the lesson 1. To form practical skills and abilities on the methods of working with a manual hand-saw when cutting strip steel, bars of various sections and pipes.
The student must: Be able to: perform locksmith processing of parts using universal equipment; Safe working conditions when working with tools. Know:. Purpose, device and rules for the use of locksmith and control and measuring tools and devices Observe and understand the purpose of practical activities. Analyze working methods. Use measuring tools.
Lesson progress Organizational moment (2-3 minutes) Introductory briefing (30-35 minutes) Presentation of the topic Message of the goal and objectives of the lesson Updating the passed material Presentation of new material: (according to the presentation) Consolidation of new material
Actualization of the passed material a) How to organize a workplace when cutting metal with scissors? b) How are hand held metal shears classified? c) Why, when cutting sheet metal with hand scissors, do they sometimes “crumple” the metal, and not cut? How can you avoid this? d) Safety when cutting sheet metal with hand scissors?
Presentation of new material: 1. Purpose of the hacksaw 2. Types of hacksaws 3. Installation of the blade in the frame (machine) of the hacksaw. 4. Working posture when cutting with a hacksaw. 5. The position of the hands (grip) when cutting 6. The process of cutting with a hand hacksaw 7. General technical requirements for cutting with a hacksaw. 8. Cutting round metal. 9. Cutting pipes. 10.Cutting strip and square metal. 11. Cutting of the shaped profile. 12.Safety when filing
Purpose of a hacksaw A hand hacksaw for metal is used for cutting thick sheets of strip, round and profile metal, as well as for cutting slots, grooves, trimming and cutting out workpieces along the contour
Types of hacksaws: 1.One-piece hacksaw
Installing the blade in the frame The hacksaw blade is inserted into the slots of the machine head 2,3 so that the teeth are directed away from the handle and not towards the handle. Tighten the hacksaw blade manually with a tensioning screw 1, without great effort. Check the degree of tension by lightly pressing your finger on the blade from the side: if the blade does not bend, then the tension is sufficient. Do not under any circumstances allow a very strong or very weak tension of the canvas, because it will break it.
Working posture when cutting metal with a hacksaw Set the height of the vise for growth (a) Stand in front of the vise freely and steadily. Expand the body to the left of the vise at an angle of 45⁰ (b) Extend the left leg slightly forward and transfer the weight of the body onto it. Turn the right leg in relation to the left leg at an angle of 60-70⁰ while the distance between the heels should be 200-300mm.
Hand position (grip) when cutting. Grasp the handle of the hacksaw with the fingers of your right hand, the end of the handle should rest against your palm Hold the frame of the hacksaw with your left hand, as shown in the figures, with four fingers grasp the lamb and the tension bolt
The process of cutting with a hand hacksaw The cutting process consists of two steps: the worker, when the hacksaw moves forward from the worker, and the idle one, when the hacksaw moves backward relative to the worker. The entire hacksaw blade should be involved in the work, they work with the hacksaw smoothly, without jerking, making 40-50 working movements per minute. Before finishing the cut, loosen the pressure on the hacksaw to avoid injury.
Hack saw tutorial
General technical requirements for cutting with a hacksaw. They work with a hacksaw slowly, smoothly, without jerking, making no more than 30-60 double strokes per minute. At a faster pace, the web heats up and dulls quickly; Before the end of the cut, weaken the pressure on the hacksaw in order to avoid the blade breaking; When cutting, do not allow the blade to heat up, periodically lubricating it with mineral oil or graphite grease, especially when cutting viscous metals; Brass and bronze are cut only with new blades, since even little-worn teeth do not cut these metals, but slide over their surface. For long cuts, use a hacksaw blade with a large pitch, and for short cuts, use a fine pitch; In the work, the hacksaw blade must participate along its entire length;
A river of round metal. Mark with chalk the place of cutting on all sides of the part. Fix the part in a vice so that the cutting line is to the left, 15-20 mm from the vice jaws. Cut the bar, observing the following rules: at the beginning of cutting, tilt the hacksaw slightly away from you;. during operation, the hacksaw blade is in a horizontal position;. at least 3/4 of the blade length should be involved in the work;. make 40-50 working movements per minute;. press the hacksaw lightly and only when moving forward.
Cut the pipe. Fix the pipe in a vise or pipe clamp. When clamping a thin-walled pipe or pipe with a clean surface, use wood spacers. Mark the cutting line around the circumference of the pipe. Cut the pipe, observing all the previously indicated rules
Cutting strip and square metal Thinner material is clamped between pieces of wood (see picture on the right). Thin workpieces are collected in packages, that is, several pieces are put together and fixed in a vice. At the beginning of cutting strip and square products, the hacksaw is tilted slightly forward. Gradually, the slope is reduced and after the cut reaches the nearest edge of the workpiece, the hacksaw is returned to a horizontal position. It is necessary to ensure that the marking of the risk is preserved. If you cut exactly according to the marking risk, then after sawing off the size of the part will be less than the one specified in the drawing, which will lead to irreparable rejects.
When cutting with a hacksaw, it is recommended to fix the blanks of the shaped profile (corner, channel, etc.) in wooden mouthpieces (see fig. Ref. The blank must be securely fastened in a vice. Work with a hacksaw should be smooth, without jerks. bottom cut-off part.
The material to be cut must be clamped very securely in the vice. The blade should not be too tight on the hacksaw, but not too loose. Protect hands from injury from the cutting edges of the hacksaw and burrs on the metal. Observe the position of the fingers of the left hand, supporting the sheet from below. Do not blow away or remove sawdust with your hands to avoid clogging your eyes or injuring your hands. Do not clutter up the workplace. Safety rules when cutting metal with a hacksaw.
Questions for reinforcement 1. What are the main parts of the hacksaw and explain their purpose? 1. frame (machine). 2. handle 3. pins, slots 4. hacksaw blade 5. movable head for attaching the hacksaw blade with a slot and a pin 6. tension screw with nut
How to assemble a hacksaw? The teeth are directed away from the handle. Tighten the hacksaw blade without much effort. Check the degree of tension by lightly pressing your finger on the side of the web: if the web does not bend, then the tension is sufficient. Do not allow very strong or very weak belt tension, as this will break it. 3. How to stand at the vise when cutting metal with a hacksaw? Set the height of the vise by height: right, bent at the elbow should form a right angle (90 °) between the shoulder and the elbow; turn the body to the left of the vice at an angle of 45 °; 4. Why is it forbidden to cut metal with a weakly or strongly tensioned hacksaw blade? Doing so can break the blade and injure your hands. 5. What should be observed to avoid breakage of the hacksaw blade and injury to the hands? Do not press hard on the hacksaw. 6. Which hacksaw handle should not be used? With a loose or split handle.
Homework Pokrovsky B.S. Plumbing: A Textbook for the Beginning. professional education / B.S. Pokrovsky, V.A. Skakun. M.: Publishing Center “Academy”, 2003.-320s. P. 94-113
Hacksaw for metal
A hacksaw is probably the most famous metal cutting tool and also one of the most useful. Its hardened steel sheet will handle most metals found in or around a home; a hacksaw is able to cut metal up to a third of the length of its blade.
Hacksaw for metal
Hacksaw blades for general use have hardened teeth and are made of molybdenum, carbon or tungsten steel. The main factors when choosing a blade are the number of teeth per inch (the same parameter can simply be referred to as a tooth pitch. the distance between adjacent teeth) and a set / set of teeth. the angle at which they are located on the cutting edge.
For effective cutting, at least two teeth of the hacksaw blade must always be in contact with the metal. If the metal is too thin for two teeth to fit on its edge, when sawing, place it between two sheets of thin plywood (another option is to cut at an angle to the plane of the metal sheet).
Hacksaw for metal
The adjustable reversible hacksaw can accept blades from 25 to 30 cm in length. For blades, the number of teeth per inch can vary from 4 to 32. In general, blades with a number of teeth per inch from 4 to 16 are used for those metals that “clog” the blade with more fine teeth. Coarse-toothed blades usually have a variable set. the teeth are located in a straight line, but bent alternately in different directions. Fine-toothed blades are usually given a wavy set. their teeth are bent over a gently curving mowing line, as shown for 24 teeth per inch in the illustration above. Wavy cut produces a wider kerf to prevent blade binding.
Cold cutting metal: how to work with a hacksaw and chisel
In all applications. be it a veranda fence, a door hinge, or a hoe. metal is prized for its toughness and strength. It can withstand loads and conditions that will quickly destroy (or slowly deteriorate) most other materials. But sometimes it becomes necessary to change its size and shape, and it is quite possible to do this in a summer cottage. over, some manipulations can be performed without heating. with the help of special scissors, chisels, a hacksaw or a jigsaw. However, one cannot do without knowing at least basic techniques of working with metal. You can find a step-by-step description of them in John Keelsey’s encyclopedia “Metalworking”. We bring to your attention excerpts from this book, published by the publishing house “AST” in the series “Craftsmanship and Hobby”.
For safety reasons, avoid excessive pressure no matter how hard the metal is. Too much pressure can break the blade or knock it out of the cut; both options can be dangerous.
Sawing a curved edge with a hacksaw
Line Curve Marking
Line Curve Marking
- Set the marking compass to the desired radius and use a center punch with a hammer to mark the center of the arc.
- Place one needle of the compass in the punctured recess and, freely holding the upper end of the compass with one hand, draw with the other needle over the metal surface. Hold the compass upright, at right angles to the metal. The pressure should be no more than to line the visible mowing line.
- Clamp the workpiece in a vise with the line of the line next to the vise jaws. This will prevent the workpiece from swaying when cutting with a hacksaw.
Using a carbide-tipped string blade
Using Carbide-tipped Stringing Blades
- Holding the hacksaw with both hands, place the string against the retreat side mowing line and move the saw forward slowly. Repeat this movement, starting each stroke from the front end of the string, until it is completely immersed in the metal.
- Then move the saw slowly back and forth with light, even pressure in both directions of travel along the line mowing line. Restart the workpiece, if necessary, so that the cutting area remains close to the vise jaws.
In fact, no saw can handle all possible cuts in metal. For example, cuts from the center of a sheet / plate are often beyond the reach of a classic hacksaw blade because the frame (machine) limits access. For such work, you need to use either a hacksaw-handle (without a frame) or a metal chisel.
Tools for cold cutting metal to size
It seems paradoxical that a material that is prized primarily for its resistance to cutting, kinking and bending can be easily processed. Nevertheless, with well-sharpened tools and the appropriate methods, the metal can be processed surprisingly well. For projects involving common materials such as cast iron or mild steel, sawing, chopping and filing are basic machining operations.
The metal is surprisingly easy to work with. The main thing is skill and a well-sharpened tool
Some power tools may be used to cut metal. Jigsaws, hacksaws and band saws can be equipped with special blades and saws. There are also special mechanical hacksaws for metal. They are excellent at straight cuts, but are expensive and cannot make curved cuts.
Straight cuts with a hacksaw
Cut across a narrow strip
Cut across a narrow strip
- Clamp the workpiece in a vice so that the line marking the cut is located vertically and next to the jaws of the vice.
- Place the bar against the cut-off side of the cut-off line and pull lightly over the metal so that the teeth begin to cut into the edge.
- Then, using both hands, cut along the line. Push the tool forward with slight, even pressure, and reverse without pressure. Let the canvas do the work itself; do not try to cut deeper with each hacksaw stroke.
- As you approach the end of the cut, hold the waste metal with your hand to prevent vibration and galling.
- Make the last moves before separating the waste short.
Long edge cutting
Long edge cutting
- Clamp the workpiece in a vice in the same way as for the cross cut, so that the cut line runs vertically.
- Turn the hacksaw blade perpendicular to its frame and hold the frame horizontally; in this position, the frame will not interfere with the movement of the blade along the workpiece.
- Start cutting in the same way as for the cross cut, and also support the retreat with one hand until the cut is complete.
Marking lines at an angle
Marking lines at an angle
Use the combined goniometer and scribe to mark the cut lines.
- To position the lines correctly, first mark the top of the cutout with a center punch and hammer.
- Then set the protractor head to the desired angle and press it against the edge of the workpiece, which should hang slightly from the edge of the workbench.
- Move the protractor along the edge until the ruler is over the center mark and draw the first line to mark the cut.
- Then, if you need to readjust the protractor, adjust the head to the angle you want for the second cut line mowing line and repeat the marking process.
- Clamp the workpiece in a vise so that one line of the cutout is vertical and as close to the vise jaws as possible.
- Support the blade with your free thumb to start the cut; otherwise, the blade may slip along the slanted edge of the workpiece. When the teeth cut into the metal, cut lightly forward until you reach the intersection point. If necessary, slide the workpiece in a vise to keep the cutting line close to the jaws.
- Then turn the workpiece over so that the second line of the line becomes vertical, and continue in the same order, again holding the blade until the teeth cut into the metal.
- When approaching the intersection of the marking lines, hold the triangular retreat with one hand and shorten the hacksaw strokes.
Locksmith chisel and its varieties
Chisels for metal come in different lengths and vary in width from 3 to 25 mm. It is customary to subdivide them into several main types, differing in shape depending on their tasks:
- locksmith chisels,
- grooves (for cutting grooves of various profiles),
- kreutzmeisel (a kind of ditch),
- blacksmith chisel (with a long wooden handle),
- nibbling chisel and undercutting (for cutting curly lines in sheet material),
- barbs / punches (for punching round holes in thin sheet material),
- center punch / mechanical self-center punch (for small recesses in which the drill is installed).
Chisels can be different depending on the type of work they perform
In the Russian Federation, the parameters of chisels are determined by GOSTs (for example, GOST 7212-74. crosscutters, GOST 7211-86. chisels, etc.).
When cutting metal, you will need 4 types of chisels: wide, pointed, crosscutter and semicircular chisel-groove. Metal chisels can be used not only for straight chopping or cutting, but also for shaping metal, as well as for cleaning edges and surfaces. Varieties of chisels for metal
- The most common type of chisel has a straight cutting edge with a wedge-shaped sharpening. It is used for shaping, shearing metal bars, shearing bolt heads or rivets.
- The cross cutter also has a wedge-shaped sharpening, but the cutting edge is much narrower; they make grooves or channels.
- The semi-circular chisel-groove is useful for rounding the inner corners of a groove or groove and for punching out semi-circular grooves.
- A pointed chisel is sharpened to a point. Used to align corners and cut narrow grooves in metal.
For safe and efficient work, the chisel must be sharp with a hardened cutting edge sharpened at an angle of 60-70 °.