Cutting with hand scissors cutting with a hacksaw
Methodical development of the lesson “Cutting metal
Metal cutting. it is an operation to separate metal blanks into parts. Depending on the shape and size of the workpieces, cutting is carried out with a hand hacksaw, hand, power or lever scissors.
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ORE TECHNOLOGYALAR MEN KYZMET KURSETU COLLEGES
RUDNENSKY COLLEGE OF TECHNOLOGY AND SERVICE
Kazakhstan Respubliki Bilim Zhane Gylym Ministirligi
Kostanay oblysy Ukimdiginin bilim Basgarmasy
Lesson type: combined (repetition of the passed material, learning new and its consolidation)
Teaching Methods: Interactive Methods
Updating the basic knowledge of students: checking homework 10 min.
Consolidation of the studied material. 10 min.
Mark absent students in the lesson.
Message of the topic of the lesson and clarification of goals. (Slide 1,2,3,4)
Homework check. Questions on the topic covered:
Question 1. What kind of plumbing operation is called flexible?
Supposed answer: Flexible. a method of processing metal by pressure, in which a workpiece or part of it is given a curved shape.
Question 2. What is the essence of metal bending?
The essence of bending lies in the fact that one part of the workpiece is bent in relation to the other at a given angle.
Question 3. What tools and devices are used when bending metal?
Supposed answer: Bending is carried out both manually on a support tool and mandrels, and on bending machines, presses. With thick workpieces, bending is carried out by blows of a hammer, preferably a wooden one, which does not leave impact marks on the metal. The wire is bent with pliers or round nose pliers.
Question 4. What are the ways to bend strip metal?
Estimated answer: Having fixed the metal blank in a vice, bending is carried out by hammering it at a given angle. Also, strip metal can be bent with a die. Bending of strip steel on the edge is bent in a special device using rollers. Question 5. What are the ways of bending pipes?
Estimated answer: Bending of pipes is carried out:
Question 6. Name the types and causes of defects when bending metal.
Supposed answer: When bending metal, marriage is most often manifested in oblique bends and mechanical damage, as well as improper impacts. Correctly bent pipes are considered to have no dents, bulges or folds.
Question 7. What safety measures must be observed when bending metal?
Estimated answer: In order to comply with safety standards, the workpieces are firmly fixed in a vice or other devices; work only on serviceable equipment. Before starting work on bending machines:
Preparation of metal for welding involves marking, straightening, cutting, bending, edge processing, and it is also necessary to thoroughly clean the surfaces of the parts to be welded from dirt, rust, scale, oils. Straightening and bending, marking, cutting, cutting mechanical metal play an important role in the preparation of metal for welding.
During the explanation of the new material, the teacher asks the students problematic questions. Students solve situational tasks, thereby developing logical thinking, learn to reason and draw conclusions.
3.1 Cutting as a preparation stage for welding can be thermal or mechanical. In terms of productivity, thermal cutting is inferior to mechanical cutting, but it is more versatile and allows you to accurately cut out workpieces of different geometric shapes (including curvilinear ones). (The question is why?) Mechanical cutting cannot give such a result, since the capabilities of scissors and presses are limited.
3.2 Cutting metal. it is an operation to separate metal blanks into parts. Depending on the shape and size of the workpieces, cutting is carried out with a hand hacksaw, hand, power or lever scissors. (Slide 5)
For cutting thick sheets of strip or profile metal, for cutting out workpieces along the contour, a hacksaw for metal, consisting of a frame (machine) and a blade, is used. (Question: What are the main parts of a hacksaw for metal?)
Hacksaw blades are made of carbon steel or hardened steel (Question: in connection with what is this connected?); their teeth are wedge-shaped; overall dimensions. 150-300 x 10-25 x 0.6-1.2 mm. The teeth of the blades can be large and small, with a pitch between each other from 0.8 to 1.5 mm (while for cutting sheet iron, blades are used with a pitch between the teeth of 0.8 mm; for thin-walled pipes, thin profile metal. 1 mm ; for profiled rolled steel, pipes and non-ferrous metals. 1.25 mm; for cast iron and mild steel. 1.2-1.5 mm).
3.4 Working posture when cutting metal with a hacksaw (Slide 7)
a) set the height of the vise in terms of growth: the right hand with a hacksaw, installed on the jaw of the vise (in its original position), bent at the elbow should form a right angle (90 °) between the shoulder and the elbow;
b) stand in front of the vise freely and steadily, half-turn in relation to the vise jaws or to the axis of the object being cut;
c) turn the body to the left of the vice at an angle of 45 °;
d) put the left leg forward a little, approximately along the mowing line of the object to be cut and rest the body on it.
Movements with a hacksaw must be done smoothly, without jerking; frequency of movements. 30-60 double strokes (from oneself. to oneself) per minute; in this case, at least 2/3 of the blade length should work. The hacksaw blade must be strictly perpendicular to the axis of the workpiece being processed.
3.5 Position of hands (grip) when cutting metal with a hacksaw (Slide 8)
Hand position (grip) when cutting metal:
a) the handle of the hacksaw is grasped with the fingers of the right hand (the thumb is placed on top, the rest of the fingers support the handle from below), the end of the handle rests on the palm. Do not stretch your index finger along the handle and grip the handle deeply, as the end of it will come out of the hand, which can lead to hand injury when working;
b) hold the hacksaw frame with your left hand, as shown in the figure. Grasp the movable head and tension bolt with four fingers, not just the frame; otherwise it will be difficult to eliminate the jiggle of the hacksaw during operation.
3.6 Cutting round blanks (Slide 9)
(Question: what do you think, what difficulties can arise when cutting round workpieces? What needs to be done to prevent this?) When cutting, round blanks are pre-marked, clamped in a vice and for a better direction of the hacksaw blade, a shallow groove is made with a file along the marking risk. On an unmarked workpiece, a thumb of the left hand is placed at the place of the cut, a hacksaw is tightly attached to its nail, and a hacksaw is moved with the right hand.
3.7 Cutting square metal and strips (Slide 10)
When cutting a square metal or strip at the beginning of the operation, the hacksaw is tilted forward and then cut with the tool in a horizontal position. It is advisable to cut the strip along the narrow side.
Power scissors are used when it is necessary to cut metal with a thickness of 1.5-2.5 mm.
Lever shears cut sheet metal up to 4 mm and soft metal up to 6 mm.
Hand scissors are used when cutting metal with a thickness of 0.5–1.5 mm. In this case, the blades of the scissors should be diluted by about three quarters of their length, and the sheet of metal should be positioned perpendicular to the plane of the cutting edges of the scissors. When squeezing the handles of the scissors, the blades should not be fully brought together, as this leads to the metal breaking at the end of the cut.
3.11 Types of hand scissors (Slide 14,15,16)
Thin sheet metal is most commonly cut with hand scissors. There are straight right and left hand shears. For the right scissors, the upper blade (in relation to the lower) is on the right, and for the left. left.
There are also scissors with curved blades specifically for cutting sheet metal along curved lines.
In most cases, right-hand scissors are used, since the mowing lines are clearly visible when working with them. Left-hand scissors are used when cutting curved parts, while cutting in the clockwise direction, positioning the scissors so that they do not cover the marking line with the blade of the mowing line. If the same operation is done with right-hand scissors, then cutting is carried out in a counterclockwise direction. Shears with curved blades are only intended for cutting sheet metal along curved lines.
When cutting metal, the following safety precautions must be followed:
Consolidation of the studied material.
Give the definition of metal cutting plumbing?
For what purposes is a hacksaw used for metal?
List the types of scissors used when cutting metal?
Two students on the interactive whiteboard are invited to fill out the table (slide 18), and all the other students are divided into three groups, they are given task cards that must be filled out:
Assignment: “Types of scissors used when cutting metal”:
Post grades. Mark the most active students.
Cutting metal with a hacksaw
Cutting metal with hand scissors.
Manual scissors are used to cut steel sheets with a thickness of 0.5. 1.0 mm and non-ferrous metals up to 1.5 mm. Manual shears are made with straight and curved cutting blades. According to the location of the cutting edge of the blade, hand scissors are divided into right and left. Right scissors are called scissors in which the bevel on the cutting part of each half is on the right side. With the right scissors, cut along the left edge of the product in the clockwise direction. Left scissors are called scissors, in which on the cutting part of each half the bevel is located on the left side. With such scissors they cut along the right edge of the product counterclockwise.
When cutting the sheet with the right scissors, the risk on the cut metal is always visible. When working with left scissors, in order to see the risk, you have to bend the cut metal with your left hand, shifting it over your right hand, which is very inconvenient. Therefore, sheet metal along a straight mowing line and along a curve (circle, rounding) without sharp turns is cut with right-hand scissors.
A hand saw (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. A 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 a 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 spread 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. Most often, hacksaw blades are used for hand hacksaws with a length L. 250. 300 mm, a height L. 13 and 16 mm, a thickness h. 0.65 and 0.8 mm. Each tooth of a hacksaw blade is wedge-shaped. On the tooth, as well 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 values of 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.
Manual locksaw hacksaw (machine): a. solid, b. sliding, c. with a movable holder, d. hacksaw blade;
Preparing the hacksaw
Working position when cutting with a hacksaw
a) set the height of the vise for growth. the right hand with a hacksaw should have an angle of 90 ° at the elbow. See the picture above.
b) stand in front of the vise freely and steadily, half-turn in relation to the vise jaws or to the axis of the object being cut
c) turn the body to the left of the vice at an angle of 45 °
d) put the left leg forward a little, approximately along the mowing line of the object to be cut and rest the body on it
e) the right leg should be turned in relation to the left at an angle of 60-70 °, while the distance between the heels should be 200-300 mm
Cutting strip and square metal
Fix the workpiece in a vise so that it protrudes 15-20 mm above the vise jaws and the cutting line is perpendicular to the vise jaws.
Make a shallow cut with a triangular file in the place of the cut for a better direction of the hacksaw.
At the beginning of the cut, tilt the hacksaw slightly away from you (or towards yourself). As the cut progresses, gradually reduce the incline until the cut reaches the opposite edge of the workpiece. Then carry out cutting with the horizontal position of the hacksaw.
Cut metal not across the width, but along the narrow side; this, however, can only be tolerated if the side width is greater than 2.5 tooth pitch.
Note. The hacksaw can only cut strip material if its thickness is greater than the distance of three teeth of the hacksaw blade. The thinner material is clamped in a vice between two pieces of wood and cut.
Cutting metal without turning the hacksaw blade
a) apply chalk markings to the risk of the cut;
b) fix the part in a vise in a horizontal position so that the cut-off part is to the right or left of the vise. the cutting line should be 15-20 mm from the vise jaws;
c) make a small (1.5-2 mm) cut in the place of cutting with a triangular file according to the marking risk, so that the hacksaw blade does not slip at the beginning of cutting, but cuts into the part.
Smallest Chainsaw
For the correct start of cutting on an unmarked part, at the place of the cut, place the thumb of the left hand with a fingernail and press the hacksaw blade close to the nail, hold the hacksaw only with the right hand. The index finger of this hand is extended along the side of the arm. This ensures a stable position of the hacksaw during the start of the cut;
d) when cutting, observe the following rules: at least 3/4 of the hacksaw blade must be involved in the work; do 40-50 working movements per minute; press on the hacksaw only when moving forward; when finishing cutting, support the piece to be cut with your hand.
Cutting pipes with a hacksaw
Clamp the pipe in a vise in a wooden block (fig.d) or in special clamps (fig.d) so as not to crush the pipe.
Cut with a fine-toothed hacksaw blade.
Hold the hacksaw horizontally when starting cutting. After the teeth of the blade enter the metal, the hacksaw should be tilted towards you and, from time to time, turning the workpiece at an angle of 45-90 ° away from you, continue cutting.
The number of double strokes should be 35-45 per minute.
Choosing a hacksaw blade:
a) for cutting soft metal, use hacksaw blades with a large pitch s (16-18 teeth per 1 inch); for cutting thin strip metal. fine-toothed hacksaw blades (22-23 teeth per 1 inch), and for cutting the thinnest sheet metal. 24-32 teeth per 1 inch;
b) for locksmith work, they mainly use a hacksaw blade with a pitch of s = 1.5 mm, at which there are about 17 teeth on a length of 25 mm;
c) for long sawing, take hacksaw blades with a large step, and for a short one. with a small step;
d) hacksaw blades are produced with a sharpening angle of 43-60 °. To cut harder metal, use blades with a greater angle of taper, and less for cutting soft metals. Blades with a large taper angle are more wear-resistant.
Cutting metal by turning the hacksaw blade
A hacksaw with a blade turned at an angle of 90 ° is used to cut when the depth of the cut exceeds the distance from the blade to the frame of the hacksaw machine (Fig.a), that is, with deep cuts.
Assembling a hacksaw with a 90 ° blade turn:
a) release the lamb and remove the blade from the machine;
b) insert the blade into the slots of the shank so that in the working position the frame of the hacksaw blade is horizontal (Fig. b, c)
c) insert the pins and tighten the canvas with a thumbscrew.
Metal cutting
Cutting, or cutting, is the separation of parts (blanks) from bar or sheet metal. Cutting is carried out both with the removal of shavings (with a hand hacksaw, on hacksaw, circular saws, turning-cutting machines, as well as gas, arc cutting and other methods), and without removal (with manual lever and mechanical scissors, nippers, pipe cutters, press-shears, stamps). Cutting also includes metal notching.
Scissor cutting
The essence of the scissor cutting process is the separation of metal parts under the pressure of a pair of cutting knives. The sheet to be cut is placed between the upper and lower knives. The upper knife, going down, presses on the metal and cuts it.
Knives are made of U7, U8 steel. The side surfaces of the blades are hardened to 52.58 HRC, they must be ground and sharpened.
Manual scissors (Fig.10.1) are used to cut sheets of steel with a thickness of 0.5. 1.0 mm and from non-ferrous metals up to 1.5 mm thick. Manual shears are made with straight and curved cutting blades.
According to the location of the cutting edge of the blade, hand scissors are divided:
- on the rights, in which the bevel on the cutting part of each half is on the right side. With right scissors, cut along the left edge of the product in the clockwise direction;
- left, in which on the cutting part of each half the bevel is located on the left side. With such scissors they cut along the right edge of the product counterclockwise.
When cutting the sheet with the right scissors, the risk on the cut metal is always visible. When working with left scissors, in order to see the risk, you have to bend the cut metal with your left hand, shifting it over your right hand, which is very inconvenient. Therefore, sheet metal along a straight mowing line and along a curve (circle, rounding) without sharp turns is cut with right-hand scissors.
The length of the scissors is 200, 250, 320, 360 and 400 mm, and the cutting part (from the sharp ends to the hinge) is 55.65, 70.82, 90.105, 100.120 and PO, respectively. 130 mm. Well-sharpened and well-adjusted scissors should cut the paper.
Hand-held small-sized power shears are designed for cutting sheet steel up to 2.5 mm thick, bars, bolts (studs) up to 8 mm in diameter. The dimensions of these scissors do not exceed the dimensions of standard hand scissors. Cutting handle one fixed in a vice, and the handle eight (working) is put into action (fig. 10.2). The working handle is a system of two levers connected in series.
First lever 6, on one shoulder of which a knife is fixed four, connected with a screw 3 with handle one. Second lever arm 6, which is a handle for conventional scissors, is made shortened and ends with a hinge 7, or the actual handle of the scissors. End-hinge handle eight with a double-pivot link 2 connected to the handle one. This system of levers increases the cutting force about twice that of a conventional shear of the same size. Scissor knives are interchangeable and attached to levers with blind rivets.
The shears are also equipped with a device for cutting bars with a diameter of up to 8 mm. The device has discs 5 with holes, fixed on the arms of the scissors, and is a conventional scissors, but with knives of a special shape (hardened bushings). These knives are replaceable and fit into the disc slot. For cutting bolts (pins) in the bushings of one of the discs there is a thread (several threads), which protects the thread of the bolts during cutting from crushing.
Lever shears are used to cut sheet steel up to 4 mm thick, aluminum and brass up to 6 mm thick. The upper articulated knife is operated from the lever, the lower knife is fixed.
Knives are made of U8 steel and hardened to a hardness of 52. 60 HRC. Sharpening angles of cutting edges 75.85 °.
Before work, check whether the rubbing parts are lubricated, whether the lever moves smoothly, whether there is no gap between the cutting edges.
Shears with inclined knives (guillotine) allow you to cut sheet metal with dimensions of 1000. 3200 mm and a thickness of up to 32 mm, less often. strip products, as well as sheet non-metallic materials.
HACKSAW CUTTING
General information. A hand saw (saw) is a tool designed 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 and other works. Hand locksaw hacksaw (Fig. 1.41, but) consists of a machine (frame) 2 and hacksaw blade four. There is a fixed head at one end of the frame five with shank and handle 6, and on the other. a movable head 3 with tension screw nine and nut (wing) one for tensioning the web. In heads five and 3 slots made eight, into which the hacksaw blade is inserted and fastened with pins 7.
one. wing nut, 2. frame (machine), 3, 5. movable and fixed head,
four. hacksaw blade, 6. shank with handle, 7.pins, eight. slits,
nine. tension screw, 10. movable bracket
A hacksaw blade is a thin and narrow steel plate with two holes and teeth on one of the ribs. Blades are made of U10A and Kh6VF steels, their hardness is HRCe 61. 64. Depending on the purpose, hacksaw blades are divided into manual and machine blades. The blade is inserted into the frame, teeth first.
The size (length) of a hand hacksaw blade is determined by the distance between the centers of the holes for the pins (Fig. 1.43, b). The most commonly used hacksaw blades for hand hacksaws length L, equal to 250.300 mm, height b, equal to 13 and 16 mm, thickness h, equal to 0.65 and 0.8 mm.
Each tooth of a hacksaw blade is wedge-shaped. On the tooth, as well as on the incisor, the rear angle α, the angle of sharpening β and the front angle γ are distinguished; α β γ = 90 °.
Setting the teeth of the hacksaw blade. When cutting with a hand hacksaw, at least two or three teeth must be involved (cut metal at the same time). To avoid jamming (jamming) of the hacksaw blade in the metal, the teeth are set apart so that the width of the cut made with the hacksaw is slightly greater than the thickness of the blade. It also makes the job much easier.
Depending on the step value S the wiring is performed along the canvas and along the tooth. Hacksaw blades with S = 0.8 mm, must have a set of teeth along the blade (Fig. 1.44, but), i.e. every two adjacent teeth are bent in opposite directions by 0.25. 0.6 mm. (This layout, also called wavy, is also allowed when S = 1 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.
Canvases with S 0.8 mm, bred to the tooth (Fig. 1.44, b); such a wiring is called corrugated. With a small tooth pitch, two or three teeth are retracted to the right and two or three. to the left. With an average step, one tooth is retracted to the left, the second. to the right, the third is not taken away. With a large step, one tooth is retracted to the left, and the second. to the right. Typically, the tooth setting is used for canvases with a tooth pitch of 1.25 or 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, the material to be cut is firmly fixed in a vice (the level of fastening 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, hacksaw blades with a large tooth pitch are used, and for short ones. with small.
The hacksaw blade is installed in the slot of the head so that the teeth are directed away from the handle, and not towards it. In this case, first insert the end of the web into the fixed head and fix it with a pin, then insert the second end of the web into the slot of the movable pin and also fix it with a pin. Stretch the canvas by hand without much effort (the use of pliers, vices, etc. is prohibited) by rotating the wing nut. At the same time, due to the fear of rupture of the blade, the hacksaw is kept away from the face.
Date Added: 2015-08-05; views: 16; Copyright infringement
Wood and metal processing
Manual notaries are used to cut steel sheets with a thickness of 0.5. 1.0 mm and from non-ferrous metals up to 1.5 mm. Manual shears are made with straight and curved cutting blades.,
By the location of the cutting edge of the blade, manual scissors are divided into right and left.
Right scissors are called scissors in which the bevel on the cutting part of each half is on the right side. Right scissors cut along the left edge of the product in the clockwise direction.
Left scissors are called scissors, in which on the cutting part of each half the bevel is located on the left side. With such scissors they cut along the right edge of the product counterclockwise.
When cutting the sheet with the right scissors, the risk on the cut metal is always visible. When working with left scissors, in order to see the risk, you have to bend the cut metal with your left hand, shifting it over your right hand, which is very inconvenient. Therefore, sheet metal along a straight mowing line and along a curve (circle, rounding) without sharp turns is cut with right-hand scissors.
The scissors are held in the right hand, grasping the handles with four fingers and pressing them to the palm; the little finger is placed between the handles of the scissors.
The compressed index, ring and middle fingers are unclenched, the little finger is straightened and with its effort the lower handle of the scissors is pulled to the required angle. Holding the sheet with your left hand (Fig. 2, b), feed it between the cutting edges, directing the upper blade exactly in the middle of the marking mowing line, which should be visible during cutting. Then, squeezing the handle with all fingers of the right hand, except for the little finger, cut.
In fig. 2, c, d shows the techniques of working with scissors.
For straight cutting metal of small thickness, manual scissors are used, one handle of which is clamped in a vice.
Chair notaries differ from manual ones in large sizes and are used when cutting sheet metal up to 3 mm thick. The lower handle is rigidly clamped in a locksmith’s vice or mounted (driven in) on a table or other rigid base. For cutting sheet steel up to 3 mm thick, chair scissors are used, which have a stationary fastening (Fig. 3, c).
Chair scissors are unproductive, they require significant efforts during work, therefore they are not used to cut a large batch of sheet metal.
Hand-held small-sized power notaries. The innovator A.N. Vasiliev created small-sized power shears for cutting sheet steel up to 2.5 mm thick, bars, bolts (studs) up to 8 mm in diameter. The dimensions of these scissors do not exceed the dimensions of standard hand scissors. For cutting, the handle is fixed in a vice, and the handle (working) is activated. The operating handle is a system of two levers connected in series. The first lever, on one shoulder of which the knife is fixed, is connected with a screw to the handle.
The second arm of the lever, which is a handle for conventional scissors, is shortened and ends with a hinge, or the actual handle of the scissors. The handle is connected to the handle by means of the end hinge by means of a double-hinged link. This system of levers increases the cutting force about twice that of a conventional shear of the same size. Scissor knives are interchangeable and attached to levers with blind rivets.
These shears also have a device for cutting bars with a diameter of up to 8 mm. The device has disks with holes, fixed on the arms of the scissors, and is a regular scissor, but with knives of a special shape (hardened bushings). These knives are replaceable and fit into the disc slot. For cutting bolts (saws). in the bushings of one of the discs there is a thread (several threads), which protects the thread of the bolts during cutting from crushing.
Small power shears provide good cutting quality.
Lever shears are used to cut sheet steel up to 4 mm thick, aluminum and brass up to 6 mm thick. The upper articulated knife is operated by a lever. Lower knife. fixed.
Knives are made of U8 steel and hardened to a hardness of HR.C 52. 60. Cutting edges taper angles 75. 85 °.
Before work, check whether the rubbing parts are lubricated, whether the lever moves smoothly, whether there is no gap between the cutting edges.
When cutting metal with the right hand, grasp the handle of the lever and smoothly move it to the upper position, while the upper knife 3 moves up. Then the sheet is laid so that the left hand holds it in a horizontal position, and the cut line is in the field of view and coincides with the blade of the upper knife. With a movement of the hand, the lever with the knife is lowered down until a part of the metal is cut, after which the lever is moved to the upper position. Next, slightly lift sheet 4 with your left hand, advance it along the risk along the cutting edge of the upper knife and repeat the cutting technique until it is completely cut. Scissors ensure a dents-free cuts, no cuts along the edge and sufficient accuracy.
STRAIGHT CUTTING DEVICE FOR HACKSAW
Flywheel shears are widely used for cutting sheet metal with a thickness of 1.5-2.5 mm with a tensile strength of 450-500 MPa (45-50 kgf / mm2) (steel, duralumin, etc.). These scissors cut metal of considerable length. Lever shears have a cast-iron bed and a table, a lower fixed knife is built into the table, and an upper movable knife with a curved cutting edge is fixed in the knife holder. The upper movable knife has a counterweight counterbalancing the knife holder with the knife.
The size of the workpieces to be cut is outlined by preliminary marking or limited by an adjustable stop, for which the stop is first set at the required distance from the cutting edge of the lower fixed knife. During cutting, the sheet is pressed tightly with its lateral edge against the stop, and with the other edge against the spring stop. After that, by turning the handle away from you, the sheet is tightly pressed from above with a clamping bar and, lowering the upper nose with a knife holder 6, cut the workpiece.
When lowering the knife holder, it rests against the spring stop. The stop is repositioned using the handle.
Shears with inclined knives (guillotine) allow you to cut sheet metal up to 32 mm thick, sheets with dimensions 1000. 3200 mm, less often strip products, as well as sheet non-metallic materials.
Cutting with hand scissors
Cutting, or cutting, is the separation of parts (blanks) from bar or sheet metal. Cutting is performed both with and without chip removal. Methods of cutting with the removal of shavings: manual hacksaw, on hacksaw, circular saws, turning-cutting machines, as well as gas, arc cutting and other methods.
Without removing the shavings, materials are cut with manual lever and mechanical shears, nippers, pipe cutters, press shears, and stamps. Cutting also includes metal notching.
The essence of the scissor cutting process is the separation of metal parts under the pressure of a pair of cutting knives. The sheet to be cut is placed between the upper and lower knives.
The upper knife, going down, presses on the metal and cuts it.
The high pressure exerted by the blades when cutting requires a large taper angle. The harder the cut metal, the greater the angle of the blade; for soft metals (copper, etc.) it is equal to 65 °, for metals of medium hardness. 70. 75 ° and for solid. 80.85 °. In order to reduce friction of the knife blades on the cut metal, the blades are given a small clearance angle α (1.5. 3 °).
Knives are made of U7, U8 steel; the side surfaces of the blades are hardened to HRC 52.58, ground and sharpened.
Hand shears are used to cut steel sheets with a thickness of 0.5. 1.0 mm and from non-ferrous metals up to 1.5 mm. Manual shears are made with straight and curved cutting blades.
By the location of the cutting edge of the blade, manual scissors are divided into right and left.
Right scissors are called scissors in which the bevel on the cutting part of each half is on the right side. Right scissors cut along the left edge of the product in the clockwise direction.
Left scissors are called scissors, in which on the cutting part of each half the bevel is located on the left side. With such scissors they cut along the right edge of the product counterclockwise.
When cutting the sheet with the right scissors, the risk on the cut metal is always visible. When working with left scissors, in order to see the risk, you have to bend the cut metal with your left hand, shifting it over your right hand, which is very inconvenient. Therefore, sheet metal along a straight mowing line and along a curve (circle, rounding) without sharp turns is cut with right-hand scissors.
The length of the scissors I1 is 200, 250, 320, 360 and 400 mm, and the length of the cutting part I2 (from the sharp ends to the hinge) is 55. 65, respectively; 70.82; 90-105; 100.120 and 110.130 mm. Well-sharpened and well-adjusted scissors should cut the paper.
The scissors are held in the right hand, grasping the handles with four fingers and pressing them to the palm; the little finger is placed between the handles of the scissors.
The compressed index, ring and middle fingers are unclenched, straightened with the little finger and by his effort the lower handle of the scissors is pulled back to the required angle. Holding the sheet with your left hand, feed it between the cutting edges, guiding the upper blade exactly in the middle of the mowing line, which should be visible when cutting. Then, squeezing the handle with all fingers of the right hand, except for the little finger, cut.
Hand hacksaw. a tool designed 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 and other works. A hand saw consists of a machine (frame) 2 and a hacksaw blade 4. At one end of the frame there is a fixed head 5 with a shank and a handle 6, and at the other end. movable head 3 with a tensioning screw and a nut (wing) 7 for tensioning the web. Heads 5 and 3 have slots into which a hacksaw blade is inserted and secured with pins 7.
Frames for hacksaws are made either in one piece (for a hacksaw blade of one specific length) (rarely), or with sliding frames that allow fixing a hacksaw blade of various lengths.
To spread the hacksaw, the knees are bent until the rivet comes out of the cutout and displaced. The rivet is inserted into another 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 or pins 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 commonly used hacksaw blades for hand saws of length I. 250.300 mm, height b. 12 and 16 mm, thickness h. 0.65 and 0.8 mm.
Topic: Locksmith operation. metal cutting
Topic: Locksmith operation. metal cutting
The essence of the process. Basic definitions. Tool Cutting with hand scissors. Cutting with a hacksaw. Cutting pipes. Mechanized Cutting Safety Guidelines for Cutting
Purpose of the lesson: to get acquainted with the techniques and sequence of performing locksmith operations metal cutting
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Cutting metal is dividing it into pieces or workpieces using a hacksaw, scissors and other cutting tools.
The operation of cutting metal in plumbing is usually used to obtain blanks for parts.
Cold cutting of metal can be done in two ways: without removing shavings. with various scissors, nippers, and with removing shavings. with a hacksaw, a cutter, a saw, etc. Mechanical (machine) cutting of metal will be discussed in Ch. 11 “Machining body parts”, and thermal cutting. in chap. 7 “Thermal cutting”.
For manual cutting of metal without removing chips, the following tools and equipment are used.
Manual scissors (Fig. 1, a) are used to cut thin sheet material up to 0.8 mm thick.
Chair scissors are used to cut sheet metal up to 3 mm thick. Lever shears (Fig. 1, b) are used for cutting metal up to 5-6 m thick. Portable scissors are used for cutting small squares (Fig. 1, c).
Tried & Tested: Cutting Metal with Hand Tools
Currently, pneumatic vibrating shears are widely used to mechanize manual metal cutting (Figure 4.10), which allow cutting metal up to 3 mm thick.
It should be noted that the named limits of the thickness of the cut metal refer to conventional steel. For other metals and alloys, these values may be higher or lower, depending on the strength of the material.
A pipe cutter with circular knives attached to the body and slider serves for cutting pipes.
Manual cutting of metal with the removal of shavings is performed using a hacksaw. The material to be cut must be clamped in a vice so that it does not vibrate when sawing (2).
They work with a hacksaw at a speed of 30-60 double strokes per minute. Hard metals are cut at a slower speed, soft metals at a higher speed. Press on the hacksaw while moving forward; do not press when reversing. At the end of the cut, the pressure is released.
If, when cutting blanks, it is not required to obtain clean ends, then it is allowed to cut the metal (round, hexagon, etc.) from several sides, without reaching the middle, for the sake of saving time, and then break off the blank.
Safety requirements when cutting metal with scissors
At enterprises, sheet material is widely used, which has a small thickness. from 0.1 to 20 mm. The simplest technique for obtaining blanks from such a material is cutting. The thinnest sheets can be processed with manual shears, thicker ones. mechanically using guillotine shears. In both cases, the worker is exposed to various undesirable production factors. Figure 20 shows manual shears for cutting metals, Figure 21. guillotine shears used in most cases, Figure 22. modern guillotine shears, developed taking into account labor protection requirements.
Manual shears for cutting metals Guillotine shears
Guillotine shears for cutting sheet metal must be equipped with:
- a table installed at the level of a fixed knife;
- guide and safety rulers, allowing you to see the place of the cut;
- adjustable stops to limit the feed of the cut sheet;
- mechanical or hydraulic clamps for fixing the cut metal;
- safety devices interlocked with the trigger mechanisms and excluding the possibility of getting the fingers of the hands working under the knives and hold-downs.
It is forbidden to cut narrow strips that cannot be pressed by the clamps. Guillotine shears should be equipped with locking disconnecting devices to turn off the electric motor during standstill or interruption in the work of the shears. Structures of scissors and safety devices ns must allow spontaneous lowering of the upper knife.
The cylindrical clamps of the guillotine shears, installed in front of the fence (protective) device of the knife zone, must be closed around the circumference with special fences, adjustable in height depending on the thickness of the material being cut.
The support surface of the scissors pedal should be straight, non-slip, have a rounded end, and a toe stop should be located at a distance of 110-130 mm from it. The pedal must be protected by a sturdy cover that is open only from the front of the service. The top edge of the cover should be rounded. The force on the scissors pedal should be in the range of 25-35 N (2.5-3.5 kg).
The supporting surface of the pedal should be installed at a height of 80-100 mm from the floor level; the inclusion of the scissors on the working stroke should take place after pressing the pedal, respectively, by 45-TO mm. The scissor pedal must be portable. Manual lever scissors must be securely attached to special stands, workbenches, tables.
Hand swing scissors should be equipped with clamps on the upper movable knife, a shock absorber to cushion the impact of the knife and a counterweight that holds the upper movable knife in a safe position.
It is prohibited to use the scissors in the presence of dents, dents or cracks in any part of the knives, as well as with blunt and loosely contacting cutting edges of the knives. In order to avoid injury to hands and to ensure free advancement, the gap between the scissors knives in the dies should be ns more than 0.05 of the thickness of the cut sheet material. When working with hand scissors, use of auxiliary levers to lengthen the handles or cutting with impacts on the blades or handles is prohibited.