Bench cutting
TO category:
Metal cutting
Bench cutting
Cutting is the process of dividing a workpiece into parts of specified sizes and shapes. Cutting is used to produce workpieces of specified sizes and shapes from rolled products and sheet metal, as well as slots and holes in the workpieces. Modern methods cutting provides high-performance processing of workpieces of almost any size and from materials with any physical and mechanical properties.
The following technological cutting methods are distinguished.
1. Sawing with hacksaws, band saws and circular saws. Used for cutting long products.
2. Cutting with scissors. Used for cutting sheet metal.
3. Cutting on metal-cutting machines (lathes, milling, etc.).
4. Anode-mechanical, electric spark and light beam (laser) cutting. These methods are used in cases where other methods do not provide sufficient productivity and the required quality. For example, they are used for cutting high-strength materials along complex and precise contours, etc.
5. Oxy-acetylene cutting. It is used for cutting workpieces of considerable thickness made of carbon steel. She doesn't provide high precision, leads to a change in the structure and chemical composition of the material at the cut site. However, it is widespread in conditions single production thanks to its simplicity, high performance and versatility.
Rice. 1. Sawing (a) and cutting workpieces with scissors (b): 1 - workpiece, 2 - knives; y - rake angle, a - rear angle, P - sharpening angle, 8 - cutting angle
Cutting can be done either manually or mechanically.
The physical essence of cutting is based on in various ways destruction of the workpiece material at the cutting site.
When sawing and cutting on metal-cutting machines, the force F applied to the cutting wedge is directed at an acute angle to the surface being processed. Therefore, the cutting wedge cuts the material and turns it into chips. When cutting with scissors, the force F applied to the cutting wedge is perpendicular to the surface being processed. Therefore, the tool cuts the material without creating chips.
Electric spark cutting is based on electrical erosion (destruction) of the workpiece material. Capacitor C, included in the charging circuit, is charged through resistor R from a direct current source with a voltage of 100-200 V. When the voltage on the electrodes (tool) and (workpiece) reaches the breakdown voltage, a spark discharge with a duration of 20-200 μs occurs between their nearest microprotrusions. The discharge temperature reaches 10,000-12,000 °C. At the point of discharge on the workpiece, an elementary volume of material instantly melts and evaporates and a hole is formed. The removed material in the form of granules remains in the dielectric medium (oil) in which the processing process takes place. Discharges following continuously one after another destroy all the workpiece material located from the tool at a distance of 0.01-0.05 mm. To continue the processing process, the electrodes must be brought closer together, which is done automatically.
Rice. 1.6. Electric spark cutting of workpieces: 1 - wire-tool, 2 - workpiece
When using oxygen-acetylene cutting, the workpiece metal at the cut site is first heated with an oxygen-acetylene flame to its ignition temperature in oxygen (for steel 1000-1200 °C). Then a stream of oxygen is directed into this place and the metal begins to burn. This generates so much heat that it is sufficient to maintain a continuous cutting process.
Anodic-mechanical cutting is based on the combined destruction of the workpiece material - electrical, chemical and mechanical. D.C, passing at the cutting site between the workpiece and the tool, causes electrical erosion of the workpiece surface. The resulting molten particles of material are removed from the processing zone by a rotating tool - a disk. At the same time, the electrolyte supplied to the processing zone is under the influence of electric current forms oxide films on the surface of the workpiece, which are removed with the same rotating tool.
Cutting tools. When sawing as cutting tools Hacksaw blades (for manual and mechanical hacksaws), band and circular saws are used. Hacksaw blades and band saws are a thin strip of high-speed or alloy (Х6ВФ, В2Ф) steel with fine teeth in the form of wedges on one or two sides. Band saws obtained by bending the tape into a ring and soldering its ends high temperature solder. A circular saw has teeth located on the periphery of the blade. The cutting teeth are hardened to a hardness of 61 - 64 HRQ. To prevent the tool from jamming in a narrow cut, its teeth are spread apart.
When choosing a sawing tool, you should first take into account the length of the cut and the hardness of the material being processed.
When making long cuts, it is necessary to choose blades with a large tooth pitch, and when processing thin-walled workpieces - with a fine one. At least three teeth must be involved in cutting simultaneously.
The higher the hardness of the material being processed, the larger the sharpening angle should be. The chips formed in this case have the shape of a comma and fit tightly into the small space. During processing soft materials Tools with large chip space should be used. A positive rake angle improves productivity because the tooth cuts rather than scrapes the workpiece material.
To process high-strength materials, hacksaw blades with synthetic diamonds on the working surface are used.
For cutting sheet material They use cutting tools in the form of knives, which are most often removable. Knives come with straight, curved and round (roller and disk) cutting edges.
In anodic-mechanical cutting, thin disks of mild steel. On an electric spark machine, a continuously moving wire is used as a cutting tool.
Equipment and devices for cutting. In a tool shop, small workpieces are cut with a hand saw. The hacksaw blade is mounted in a frame so that the teeth are directed away from the handle.
Manual lever shears are designed for cutting sheet material. Tool shops use small, portable shears. They can cut sheet steel up to 4 mm thick, aluminum and brass up to 6 mm thick.
Hand scissors are designed for cutting sheet material, making workpieces with a curved contour, cutting out holes with a complex contour in workpieces. For straight cuts, scissors with straight, wide knives are used. If the upper cutting edge is located to the right relative to the lower one, then the scissors are called right-handed, and if they are on the left - left-handed. To obtain external curved cuts, use hand scissors with curved wide knives. Cutting out internal curved contours produced with scissors with narrow curved knives.
Mechanical cutting Sheet material is cut using manual electric shears, vibrating shears, as well as roller, multi-disc and sheet shears.
Sequence and techniques of work when cutting. Cutting is preceded by marking. Then the cutting method, equipment and tools are selected.
Great importance for high-quality processing has correct execution cutting techniques. The location of the workpiece and tool during manual cutting must be such that the marking line is constantly accessible for observation. When the cutting length is large, the pressure on the hacksaw is increased, and when the length is short, it is reduced. Since the teeth of a hacksaw break especially easily at the beginning and end of a cut, at these moments the pressure on it should be minimal.
When cutting, hand scissors should be opened to 2/3 of the length of the cutting edges. In this case, they easily grip the workpiece and cut well. The cutting plane should always be perpendicular to the surface of the workpiece being cut. Misalignment leads to jamming, crushing of edges and the appearance of burrs.
Of great importance correct adjustment tool. So, with a weak tension on the hacksaw blade in a hand hacksaw, the cut is oblique. A large gap between the knives leads to the formation of burrs. The appearance of burrs with correctly adjusted knives is a signal that they have become dull.
When cutting with a hand saw, you should stand freely and straight, half-turned towards the vice.
Goal: To consolidate the skills of marking; develop skills in working with a hacksaw.
Lesson equipment: Product drawings; blanks; control squares; sets metalworking tools; hacksaws; hacksaw blades; oilers.
Posters: Sawing with a hacksaw; Safety precautions when working with a hacksaw.
Handout.
Samples of hacksaw blades and tools for cutting metal.
Time: 45 minutes.
Organizational part. Checking those present in the lesson and the availability of special clothing.
Repetition of covered material.
What alloys are classified as black?
What are the main profiles of long products?
List plumbing operations.
Explanation of new material.
A hand saw is used for cutting thick sheet, strip, round and profile metal, as well as for cutting grooves, slots in screw heads, and trimming the workpiece along the contour.
The hacksaw consists of machine (framework) and hacksaw canvases. On the machine, on one side there is a fixed head with a shank and a handle, on the other side there is a movable head with a screw for tensioning the web.
The blade is installed on the head pins so that the inclination of the teeth comes from the handle. To cut long workpieces, the blade can be fixed at an angle of 90 0. The blade must be tensioned in the machine.
divorce to reduce friction when sawing. The blades are made from tool steel grades X6VF or P9. The number and size of the blade teeth depend on the properties of the material being processed.
Briefing.
4
The cutting point should be located as close to the vice as possible.
Marking marks are applied to the workpiece. Use the edge of a file to make a depression.
When sawing metal, you must ensure that the marking lines remain intact.
When working, hold the hacksaw with both hands. They move it smoothly, without jerking. Hacksaw speed 30-60 double strokes per minute.
The hacksaw blade only cuts when moving forward. To reduce friction on the material being cut, the blade is periodically lubricated with oil.
The tilt of the blade is allowed from the plane to the edge of the workpiece. You cannot start sawing from a sharp edge.
It is necessary to support the cut piece at the end of sawing so that it does not fall on your feet.
When cutting, it is necessary to use the entire length of the hacksaw blade.
5 Securing the material. Work on task cards.
Answers on questions.
In this lesson you will make a mounting bracket. It is required to perform repair work At school. It can be used to repair school desks and furniture in school classrooms. The product is made from rolled steel.
The first thing we start work with is choosing a workpiece.
The length of the corner is given in the drawing. The marking is done with a scriber using a ruler and a square.
The size is laid down once along the ruler, then with the help of a scoring square it is transferred to the entire surface of the workpiece.
We make the cut with a file from the side of the line (from the waste side). Possible defect - sawing not along the marking line, due to inattention or poorly tensioned blade.
At the end of the work, the sawdust is removed with a sweeping brush and into a dustpan. Do not blow away sawdust as it may get into your eyes.
7. Final part.
Cleaning workplaces. Grading. Checking student work
GENERAL EVALUATION OF STUDENTS' WORK
Cutting metal with a hacksaw
1
The division of a metal workpiece into parts is carried out using a hacksaw blade, scissors or other cutting tools. Depending on the material, shape and size of the workpiece, this type of metal processing is divided into cutting with removing chips(hand hacksaw, saw, cutter) and cuttingwithout removing chips(with scissors).
A hand saw is used for cutting thick sheet, strip, round and profile metal, as well as for cutting grooves, slots in screw heads, and trimming the workpiece along the contour.
The hacksaw consists of machine (framework) and hacksaw canvases. (Fig.1)
On the machine, on one side there is a fixed head with a shank and a handle, on the other side there is a movable head with a screw for tensioning the web. The blade is installed on the head pins so that the inclination of the teeth comes from the handle. To cut long workpieces, the blade can be fixed at an angle of 90 0. The blade must be tensioned in the machine.
A hacksaw blade is a thin, narrow steel plate with teeth on one or two edges. The teeth on the blade have divorce to reduce friction when sawing. The blades are made from tool steel grades X6VF or P9. The number and size of the blade teeth depend on the properties of the material being processed.
In production, special machines and cutting wheels are used to cut workpieces.
Metal cutting techniques
The cutting point should be located as close to the vice as possible. Marking marks are applied to the workpiece. Use the edge of a file to make a depression. (Fig. 3). When sawing metal, you must ensure that the marking lines remain intact. When working, hold the hacksaw with both hands. They move it smoothly, without jerking. (Fig. 2). Hacksaw speed 30-60 double strokes per minute. To reduce friction on the material being cut, the blade is periodically lubricated with oil. The tilt of the blade is allowed from the plane to the edge of the workpiece. (Fig. 4). You cannot start sawing from a sharp edge. It is necessary to support the cut piece at the end of sawing so that it does not fall on your feet.
Possible marriage– sawing not along the marking line, due to inattention or poorly tensioned blade. Safety precautions
You cannot work with a tool that is not in good working order. (The blade is not stretched, the machine is not working properly, the teeth on the blade are painted, the blade is bent or broken). At the end of the work, the sawdust is removed with a sweeping brush and into a dustpan. Do not blow away sawdust as it may get into your eyes.
Control questions
1.How does a hacksaw work?
2. Why do they set the teeth of the blade?
3.Why is the canvas lubricated with oil?
4. How to ensure sawing exactly along the marking line?
5.What are the rules for working with a hacksaw?
Option I
1. What is the wood processing industry?
A). Forest protection
V). Lumber production
With). Wood cutting.
2. Rotation details are usually shown in drawings
A). One main view
V). Main view and top view
With). Main view and left view.
3. Each technological machine consists of at least three parts
A). Motor, spindle, feed
V). Motor, transmission mechanism, actuator
With). Feeding, control and monitoring mechanisms.
4. rental profile depends on
A). Roll diameter
V). Ingot temperatures
With). Roll shapes
5. With increasing humidity, the hardness of wood
A). Increases
V). Decreases
With). Doesn't change
6. To prevent the saw blade from jamming in the cut, make
A). Tooth set
V). Bend teeth
With). Removing teeth
7. Product made with at the lowest cost means, material, time and labor are called
A). Durable
V). Technologically advanced
With). Economical
8. Cutting a small layer of metal from workpieces with a file is
A). Sawing
V). Grinding
With). Filing
9. Annealing the workpiece reduces
A). Fragility
V). Hardness
With). Elasticity
10. The hole in the part into which the tenon fits is called
A). Nest
V). Proushina
With). Hollow
11. The main inscription of the assembly drawing is located in
A). Top right corner
V). Bottom right corner
With). Bottom left corner
12. The sharpening angle of the chisel when cutting steel should be equal to
A). 60
V). 45
With). thirty
13. By chemical composition steels are divided into
A). Carbon and heat resistant
V). Carbon and structural
With). Carbon and alloy
14. Gear parts that transmit movement are called
A). Leading
V). Transmitting
With). Slave
15. The property of wood to withstand certain loads without collapsing
A). Hardness
V). Strength
With). Elasticity
II Option
1. What do forest rangers do?
A). Forest protection and cultivation
V). Wood cutting
With). Timber harvesting
2. A product consisting of several parts is shown on
A). Technical drawing
V). Sketch
With). Assembly drawing
3. The fixed link of a mechanism or machine is called
A). The basis
V). Persistent
With). Foundation
4. Long products refer to
A). Fabricated products
V). Semi-finished products
With). Finished products
5. K physical properties wood is classified as
A). Density, hardness
V). Elasticity, smell
With). Humidity, color
6. The plane knife should protrude by an amount equal to
A). 0.1-0.3mm
V). 0.3-0.5mm
With). 0.5-0.8mm
7. Product is different uninterrupted operation, is
A). Economical
V). Technological
With). Reliable
8. Files numbered 4 and 5 refer to
A). Velvet
V). Drachov
With). Personal
9. Hardening the metal increases
A). Fragility, ductility
V). Viscosity, strength
With). Hardness, strength
10. The groove at the end of the part connected to the tenon is called
A). Nest
V). Proushina
With). Gap
11. For linear marking use
A). Vernier caliper, ruler
V). Ruler, scriber
With). Kerner, pattern
12. The sharpening angle of the chisel when cutting non-ferrous metals should be
V). 45-60
c).60-75 degrees
13. According to their purpose and application, steels are divided into
A). Structural and alloyed
V). Structural and high-tech
With). Structural and instrumental
14.Lathes are designed for processing bodies
A). Torsion
V). Rotations
With). Beats
15. For natural drying, lumber is laid in
A). Oven
V). Stack
With). pyramid
Test answers:
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1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
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14 |
15 |
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I |
IN |
A |
IN |
WITH |
IN |
A |
IN |
WITH |
IN |
A |
IN |
A |
WITH |
A |
IN |
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II |
A |
WITH |
IN |
IN |
WITH |
IN |
WITH |
A |
WITH |
IN |
IN |
A |
WITH |
IN |
IN |
Visual representation
Part drawing
Making a mounting bracket
1. Saw off a corner to the required length
ruler, scriber, hacksaw
2. File off sharp edges
file
3.Mark the center of the holes
ruler, scriber, center punch
4.drill 2 holes
drilling machine drill
5.Clean the surface of the part
sandpaper
Practical work
Agreed: at a meeting of the methodological commission.
"__" ____________ 2015
Lesson Plan #1.2
Topic studied in the program: PM 01. Metal cutting.
Lesson topic: Cutting metal with a hacksaw
The purpose of the lesson: Learn how to properly cut metal with a hacksaw.
Financially technical equipment lesson: Posters, samples,
technological maps, blanks, measuring and marking tool, workbenches, vices, scissors, pipe cutters. hacksaws.
Lesson progress: 6 hours
1. Introductory group briefing 50 min.
a) Testing knowledge of the material covered 10 min.
Sharp or by cutting , called the separation of parts (blanks) from high-quality or sheet metal.
Cutting in progress both with and without removing chips, cutting methods with removal of chips: manual hacksaw, lathe cutting machines, gas and arc cutting.
No chip removal materials are cut with hand lever and mechanical scissors, wire cutters, pipe cutters, press shears, stamps. Cutting also includes cutting metal
Hand scissors are used for cutting steel sheets thickness 0.5-1.0 mm and non-ferrous metals up to 1.5 mm. Hand scissors are made with straight and curved cutting blades.
According to the location of the cutting edge, the blades are divided into right and left.
Hand scissors consist of two levers pivotally connected to each other. The lever has a cutting edge and a handle.
Types of scissors - use chair, lever, swing, scissors with inclined knives (guillotine).
Scissor cutting process consists of separating parts of metal under steam pressure cutting knives. The sheet to be cut is placed between the upper and lower knives. The upper knife, lowering, presses on the metal and cuts it. The harder the metal being cut, the greater the sharpening angle of the blade, from 65° to 85°.
Scissor cutting techniques . 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 clenched index, ring and middle fingers unclench, straighten the little finger and, with its effort, move the lower handle of the scissors to the required angle. Holding the sheet with your left hand, feed it between the cutting edges, directing the upper blade exactly in the middle of the marking line, which should be visible when cutting. Then, holding the handle with all fingers of the right hand, except the little finger, cutting is carried out, after which the sequence is repeated.
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) or sliding, allowing for fastening.
Hacksaw blades of various lengths. To move the hacksaw apart, bend the knee until the rivet comes out of the cutout and move it. The rivet is inserted into the other notch and the knee is straightened.
Hacksaw blade - is a thin and narrow steel plate with two holes and teeth on one of the ribs.
Canvases made from steel grades U-10A, P9. 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. Hacksaw blades are most often used for hand saws long L-250-ZOOmm; height h-13 and 16 mm
thickness - 0.65 and 0.8 mm.
Hacksaw blade install 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 fabric 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.
Preparing for work with 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 according to the hardness and shape and size of the metal being cut. For long cuts, use hacksaw blades with a coarse tooth pitch, and for short cuts, with a fine tooth pitch.
Body position. When cutting metal with a hand saw, they become
in front of the vice, straight, free and stable, half a turn in relation to the jaws of the vice or the axis of the workpiece. The left leg is placed slightly forward and the body is supported on it.
Position hands (grip) The worker's posture is considered correct if right hand with a hacksaw mounted on the jaws of a vice (in its original position), bent at the elbow,
forms a right angle between the shoulder and elbow parts of the arm.
The cutting process consists of two moves: worker, when the hacksaw moves forward from the worker and single, when the hacksaw moves backwards. When idle during the working stroke, do not press on the hacksaw, but during the working stroke, use both hands to apply light pressure so that the hacksaw moves in a straight line. They work with a hacksaw slowly, smoothly without jerking.
Cutting hacksaw with blade rotation carried out with long (high) or deep cuts, when it is not possible to complete the cut due to the fact that the frame of the hacksaw rests on the end of the workpiece and interferes with further sawing. At the same time, they change the position of the workpiece and, cutting into it from the other end, finish cutting or another method, when the blade is moved 90° and cutting continues.
Round cutting metal round metal small sections are cut with hand hacksaws, and large diameters are cut on cutting machines, circular saws, etc. A marking mark is first applied to the workpiece, then the workpiece is clamped in a vice in a horizontal position and a shallow cut is made on the marks of three grains with a file.
Occupational safety when cutting metal.
- Protect your hands from injury cutting edges hacksaws and scissors or burrs on metal.
- Watch the position of the fingers of your left hand, supporting the sheet from below.
- Do not blow away sawdust or remove it by hand to avoid causing eye irritation or hand injury.
- Don't clutter workplace unnecessary tools and parts.
- Do not remove or lubricate the moving and rotating parts of the hacksaw; move the belt when working, flock.
A hand hacksaw (saw) is a tool designed for cutting thick sheets of strip, round and profile metal, as well as for cutting slots, trimming and cutting blanks for the office, etc.
6) When working, protect your hands from injury from a burr. Work with gloves.
7) When working with power tools:
a) carry out work wearing rubber gloves and on a rubber mat;
b) the body of a power tool operating at voltages above 36 V must be grounded.
c) the electrical cable to the power tool must be protected from mechanical damage (wire braid, rubber tubes, etc.)
8) When working on powered hacksaw machines:
a) do not touch the hacksaw blade with your hands when working on the machine;
b) do not leave it connected during breaks.
c) Fixing the material according to induction training. 10 min.
- What should be the pressure conditions when cutting with a hacksaw?
- Why and when to use cooling when cutting with a hacksaw.
- Why and how the teeth of a hacksaw blade are set.
- How to choose hacksaw blades when cutting different metals.
- What are the main dimensions that characterize a hand saw blade?
- Write in your notebook what effect tooth angles have on the cutting process and which ones are more rational.
- What are the causes of hacksaw blade failure?
- How to fix a hacksaw blade with broken teeth.
- How to assemble a hacksaw?
- Why are hacksaw wing nuts made with blades (explain based on the laws of physics)?
- Why is the hacksaw blade, after attaching it to the hacksaw frame, always in a tense state?
- How to stand at a vice when cutting metal with a hacksaw?
- How to hold a hacksaw with your right and left hands?
- How to organize a workplace when cutting metal and pipes with a hacksaw and pipe cutter?
- What are the features of fastening in a task for cutting with a hacksaw:
a) bar metal (square, round)?
b) strip metal?
c) sheet metal? d) pipes?
- What rules must be followed when cutting metal with a hacksaw?
- How to cut a pipe with a hacksaw?
- In what cases is metal cut with a hacksaw with the blade rotated 90°?
- What are the reasons for a hacksaw blade to break? How to avoid fabric breakages?
- How to secure a pipe in a pipe clamp?
- In what order was the pipe cut with a pipe cutter?
- Why does the pipe cutter have three, and not two or four cutting rollers?
- What safety rules must be followed when cutting metal and pipes with a hacksaw and pipe cutter?
d) Task for the day
1. Cutting metal with hacksaws to mark pipes and plates.
2. Independent work of students and ongoing instruction 4 hours 40 minutes.
(targeted walkthroughs of workplaces)
1) Check the organization of students’ workplaces
- Compliance with T.B. rules
- Check the quality of work performed
- Point out students' mistakes and how to correct them
3. Cleaning workplaces. 10 min.
1. Students clean the workplace, hand over tools and their work.
4. Final briefing. Analysis of the working day. 15 minutes.
- Celebrate the work of the best students.
- Note students' shortcomings.
- Mark students' questions.
4) Submit grades to the journal.
5. Homework assignment. 5 minutes.
Familiarization with the material of the next lesson, repeat the topic “Metal cutting”. Textbook "Plumbing" author Skakun V.A.
Master of Industrial Training_________________________________________
During metalworking and procurement work, metal is cut in cases where it is necessary to separate a part of a certain size or a given shape from a workpiece of sectional, shaped steel or pipes. This operation differs from chopping in that it is performed not by impact, but by pressing forces, and the adjacent torns of the main and separated parts of the metal have straight planes without bevels. Strip, round, angle or other steel is cut in a vice, and pipes are cut in a clamp using hand hacksaws.
Metal is cut with hand and mechanized hacksaws.
Hand hacksaws are used sliding with a horizontal or inclined handle. Hacksaws with horizontal handle consist of a left 3 and a right 5 frame, a holder 4 and a handle 7. The hacksaw blade is inserted into the slots of the head/tension screw and the head 6 of the shank. They are firmly secured with pins and tightened with a thumb 2. The hacksaw can be extended to different lengths according to the length of the hacksaw blade.
For hand hacksaws, hacksaw blades with a length of 300 mm, a width of 15 mm and a thickness of 0.8 mm are used. The sharpening angle of the hacksaw blade tooth is 60°; both hacksaw blades are moved apart so that the blade does not get stuck in the metal slot. The lower part of the blades with teeth is hardened, and the upper part is left unhardened, which reduces the breakage of hacksaw blades during operation.
When cutting metals of unequal hardness, hacksaw blades with teeth of different sizes are used. For cutting soft metals, blades with 16 teeth per 25 mm blade length are used, for harder metals (ornamental or well-annealed tool steel) - with 19 teeth, for hard metals (cast iron, tool steel) - with 22 - with two teeth 25 mm long. To cut thin strip and small angle steel, blades with 22 teeth per 22 mm of blade length are used, so that at least two or three teeth are placed across the thickness of the metal. With a larger tooth, the blades break.
The blades are inserted into hacksaws with the teeth forward. The cutting blade should not be stretched too tightly, otherwise it will break during operation.
When working, the hacksaw is held with both hands: with the right hand, by the handle, and with the left, the second end of the hacksaw is supported and a reciprocating movement is made. The position of the hacksaw when working should be closer to horizontal, so that the pressure of the worker on both ends of the hacksaw is more uniform.
When cutting, the metal is secured in a vice, and the pipes are secured in a clamp so that the cutting line is located close to the jaws of the vice or to the clamp. With this fastening, the material does not vibrate during cutting, the hacksaw blade does not break, and the cutting line is smooth. When cutting wide material, the hacksaw is held horizontally, and when cutting strip or shaped steel pipes, it is held slightly obliquely. The forward working stroke of the hacksaw is made with pressure, and the reverse (idle) stroke is made without pressure. The force of pressure depends on the hardness of the metal.
When cutting shaped and strip steel, do not press the blade very hard to avoid jamming and breaking it. At the end of cutting, you need to support the free end of the material and bring the cutting to completion. Otherwise, the material may break, pinching and breakage of the canvas. The end of the material will be uneven.
To increase labor productivity and proper organization the workplace should: prepare in advance the required number of hacksaw blades; Pre-mark the entire batch of metal to be cut and place it on the workbench on the left side of the vice; Place the material to be cut in a certain place at the workbench according to size.
When working with a hacksaw, you must following rules safety precautions: firmly fasten the handle to the shank so that it does not come off during operation and the tip of the shank does not injure your hand; The metal being cut must be firmly secured in a vice so that it does not fall out when cutting with a hacksaw and does not hurt the worker’s leg; Sweep away sawdust from the workbench with a brush.
A manual mechanized hacksaw is more productive than an ordinary one. An electric motor is mounted in the housing 6 of the hacksaw, on the shaft of which a drum having a spiral groove is mounted. A pin fits into the drum groove. When the electric motor shaft and drum rotate, the slider and the hacksaw blade attached to it move. A bar is used to support the hacksaw blade when cutting metal.
When cutting pipes manually they, as mentioned above, are secured in clamps.
Clamps can be double-column or single-column. Double-column clamps are more convenient, as they allow you to slightly lift the clamping prism, turn the screw to remove the pin from the holes and fold it back top part clamp and easily remove the pipe from it to the side.
For clamp steel pipes And pipe blanks with a diameter of 15-50 mm, pneumatic clamps of various designs are used.
Diaphragm pneumatic clamp VMS-DP-1 consists of a body, jaws with guides, steel levers (two large and two small), a flat diaphragm, a rod and a return spring. One or two layers of sheet rubber are used as a diaphragm (depending on its thickness).
Clamp the pipes by feeding them into the drive compressed air working pressure 4 kgf/cm2. The pipe is released using a spring after compressed air is released into the atmosphere.
The force of the return spring, i.e., the opening of the jaws, is adjusted with a round nut screwed into the lower part of the pneumatic chamber body.
Pneumatic clamps are used in pipe procurement shops of assembly plants when assembling assembly units.
The 872A driven hacksaw machine is designed for cutting various workpieces from section and profile metal of round and square sections. The machine bed in the upper part forms a table on which a vice is installed to strengthen the material being cut. The machine is equipped with two types of vices: with parallel jaws, in which the material is strengthened rectangular shape, and jaws with V-shaped cuts in which the material is strengthened round shape. A vice with parallel jaws rotates around an axis, which makes it possible to secure the material being cut into it under different angles(up to 45°) to the hacksaw blade.
At the top of the machine there is a trunk, which can be lowered and raised using the frame raising and lowering cylinder. The saw frame 5 with a hacksaw blade attached to it moves along the trunk guides. The frame is driven into reciprocating motion by a crank mechanism consisting of a crank and connecting rod. The hacksaw machine is driven by an electric motor 10 connected to the crank shaft by a gear transmission.
Due to the mass of the frame, the blade presses on the material being cut. Cutting occurs only when the hacksaw blade moves forward. At reverse stroke the trunk with the hacksaw blade rises slightly under the influence of oil piston pump; thereby cutting teeth less dull.
The machine is operated as follows. First, mark the cutting line on the metal or pipe being cut with chalk, then they are strengthened in the vice of the machine so that the cutting line coincides with the hacksaw blade. After this, the machine is turned on and the metal is cut.
To increase the productivity of the machine, small-sized long steel and small-diameter pipes are placed in the machine’s vice in packages of 8-14 pieces, depending on their size and cross-section, and each package is cut entirely. When cutting, the hacksaw blade is cooled by an emulsion supplied by a pump. The emulsion contains 10 l
water, 1 kg of liquid soap and 0.5 kg of drying oil. Before use, the mixture is thoroughly mixed and boiled. Disadvantages of a driven hacksaw machine: its low productivity and rapid wear of hacksaw blades.
When working on a drive machine, you must follow the following safety rules: work only on a working machine; support the cut part of the material with special stands or hands so that it does not fall on your feet; Monitor the serviceability of the electrical wiring, switch and electric motor to prevent electric shock.
Driven press shears S-229A are designed for cutting long, shaped and sheet steel up to 13 mm thick. In addition, they serve for punching round holes with a diameter of up to 20 mm with a material thickness of up to 15 mm and stamping of small-sized parts.
The machine bed 8 is mounted on a trolley 7, through which the shear press can be transported from place to place. Unit 6 for cutting sheet steel consists of a lower fixed knife, an upper movable knife and a stop, with the help of which the material to be cut is pressed against the lower knife. Unit 5 for steel cutting different profiles consists of two vertical knives having holes that correspond to different steel profiles. The machine operates from an electric motor 3 through a drive 4.
Sheet or strip steel is placed on the lower knife, pressed with a stop and, turning on the mechanism of the lower knife, it is cut. The design of the press shears allows you to cut metal of any length. Punching of holes and stamping is carried out on the hole-punching 2 and die-cutting / devices by pressing the machine switch lever.
Driven combination shear presses are portable, easy to use and suitable for work in open areas and in procurement workshops.
When working with press shears, you must follow the following safety rules: start work only if there are protective covers on the moving parts, checking the grounding of the electric motor housing; Before starting work, lubricate the shear presses and check their operation for Idling; work with installed stops for the material; when placing the processed material into the press shears, keep your hands at a safe distance from the knives and punch; remove small stamped parts only using pullers, hooks or tongs; Do not lubricate gears and other moving parts when the electric motor is running and when cutting material.
The VMS-32 pipe cutting mechanism is designed for cutting steel water and gas pipes diameter 15-50 mm. Diameter 160 mm. The gearbox is rotated using a tension screw and a steering wheel. Cutting disc rotation speed 193 rpm. The VMS-32 mechanism is driven by a 1.1 kW electric motor connected to the gearbox shaft by an elastic coupling. The cutting disk of the VMS-32 mechanism must have the correct cylindrical shape with a sharpening angle of about 60°. As the cutting blade becomes dull, it must be sharpened again. It is recommended to sharpen with a portable abrasive wheel on a flexible hose while simultaneously rotating the abrasive wheel and cutting disc. The mechanism is supplied with stands that serve as supports when cutting long pipe blanks.
The marked pipe is laid on special rollers so that the cutting line coincides with the cutting disc. Then the pipe is covered with an upper chute - a trough, it is locked with a pin and the mechanism is started. By turning the steering wheel, the cutting disc is brought closer to the pipe. The pipe rotates due to friction between it and the cutting disc. From the pressure transmitted to the rotating disk, it cuts into the metal and cuts the pipe. After cutting the pipe, by turning the steering wheel, the gearbox with the roller is moved upward.
The VMS-35 pipe cutting mechanism is designed for cutting water and gas pipes with a diameter of 15-70 mm. The pipes are cut with a cutting disc with a diameter of 160 mm, mounted on the shaft of the oscillating gearbox. When cutting, the pipe rotates. The cutting disc is fed to the pipe and returned to its original position using a pneumatic device
Metal cutting- this is dividing it into parts or blanks using a hacksaw, scissors and other cutting tools.
The operation of cutting metal in metalwork is usually used to obtain blanks for parts.
Cold cutting of metal can be done in two ways: without removing chips - with various scissors, nippers, and with removing chips - with a hacksaw, cutter, saw, etc. Mechanical (machine) cutting of metal will be discussed in Chapter. 11 “Processing of body parts”, and thermal cutting - in Ch. 7 "Thermal cutting".
For manual cutting metal without removing chips, the following tools and equipment are used.
Hand scissors (Fig. 4.9, a) are used for cutting thin sheet material up to 0.8 mm thick.
Rice. 4.9. Scissors for cutting metal:
a - manual; b - lever; c - portable for cutting angle steel.
1 - lower knife;
2 - upper knife;
3.6 - handle;
4 - intermediate lever;
5 - intermediate rod;
7 - cheek cutout.
Chair shears are used for cutting sheet metal up to 3 mm thick. Lever shears (Fig. 4.9, b) are used for cutting metal up to 5-6 m thick. Portable shears are used for cutting small squares (Fig. 4.9, c).
Currently, pneumatic vibrating shears (Fig. 4.10), which allow cutting metal up to 3 mm thick, are widely used to mechanize manual metal cutting.
Rice. 4.10. Vibrating scissors.
It should be noted that the mentioned limits for the thickness of the metal being cut refer to ordinary steel. For other metals and alloys, these values may be higher or lower, depending on the strength of the material.
For cutting pipes, use a pipe cutter with disc knives, fixed to the body and slider.
Cutting metal manually and removing chips is done using a hacksaw. The material to be cut must be secured in a vice so that it does not vibrate when sawing (Fig. 4.11).
Rice. 4.11. Correct position of the hacksaw during operation.
A hacksaw is used 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 down on the hacksaw as you move forward; When returning, do not press. At the end of cutting, the pressure is released.
If, when cutting workpieces, it is not necessary to obtain clean ends, then, in order to save time, it is permissible to cut the metal (round, hexagon, etc.) from several sides, not reaching the middle, and then break off the workpiece.
