Why is it difficult to cut sheet metal with blunt scissors?

Cold types of metal cutting

Cutting metal mechanically is a difficult process, because metal products have high strength and hardness. Cold types of metal cutting include:

Cutting with a guillotine.

This type of cutting uses special mechanical tools. scissors and metal knives. A workpiece is placed on the work table and secured with a clamping beam. Then a special blade is used to cut the skirting board. The result is a perfectly straight edge without any extra edges, burrs or nicks. The material is cut through the entire width of the sheet at once, so the curvature of the cut is zero.

difficult, sheet, metal, blunt

The following types of guillotines are currently used for cutting metal:

They do not differ in how they operate, but the last three are equipped with electronics to ensure precise, safe cutting. There are also machines that can cut not only crosswise but also lengthways. Most often the guillotine type of processing is used in preparations.

Disadvantages of this method:

  • May not be used on all metals and is limited by the thickness of the workpiece. For example, hydraulic machines are designed for metal thicknesses up to 6 mm.
  • The resulting cut blanks often are not the right size, since the accuracy of machining depends on the skill of the operator.
  • It is not possible to carry out shape cutting.
  • Cutting copper by laser: advantages and disadvantages of the technology
  • Types of metal cutting: industrial applications
  • Metal trimming from drawings: convenient and profitable

Band sawing.

Nowadays this type of metal cutting is very popular because of low cost of the equipment, good productivity and easy maintenance. The cutting tool is a band saw stretched on pulleys.

Modern band saws (Bandsaw) are supplemented by a variety of equipment and electronics, thanks to which the unit is easily integrated into the specific production line. cutting speed of this kind of machine is, on average, about 100 mm/minute and higher.

The method of cutting on the LPS allows to achieve an exact compliance with the specified parameters, and the place of the cut does not need additional processing. The method is good for high-precision products and parts with smooth surfaces. the LPS is suitable for any metal, and the cutting width is only 1.5 mm.

When this type of metal cutting, it is important to observe a number of conditions:

  • Precise selection of the saw blade tooth pitch according to the cross section of the profile to be sawn with the aid of special tables;
  • feed rate;
  • cutting speed.

LPS allows you to cut a metal workpiece at an angle, which is a big advantage compared to the guillotine.

The disadvantages of this type of metal cutting include the inability to obtain a curved cut and limiting the size of blanks, depending on the capabilities of the machine.

Metal cutting with circular saw and “angle grinder.

Precise and good cuts are made with the circular saw. This tool allows you to control the angle of the cut.

The disadvantages of this type of cutting include a large amount of waste, slow speed and shallow depth of cut.

An angle grinder can be used to cut square bars. There is no dross or oxide residue where they cut, and little residue.

But the low productivity of this type of metal cutting is its main disadvantage in comparison with other methods.

Pereosnastka.ru

Hand-operated notching machines are used for cutting of steel sheets with thickness of 0.5 to 1.0 mm and of 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 of the blade, hand scissors are divided into right-hand and left-hand.

Right-handed scissors are those with the bevel on the cutting part of each half on the right hand side. Right-handed scissors cut along the left edge of the piece in clockwise direction.

Left-handed scissors are scissors with the bevel on the left side of the cutting part of each half. They cut counter-clockwise along the right edge of the piece with such scissors.

When cutting sheet metal with right-handed scissors, you can always see the risk on the material being cut. When working with left-hand scissors, you must bend the cut sheet with your left hand and move it through your right hand to see the risk, which is very inconvenient. Therefore, sheet metal along a straight cut line and along a curve (circles, roundings) without sharp turns is cut with right scissors.

Hold the scissors in the right hand, encompassing the handles with four fingers and pressing them to the palm; put the little finger between the scissor handles.

Squeeze the index, ring and middle fingers together, straighten the little finger and use it to push the lower handle of the scissors to the desired angle. Holding the sheet with the left hand (fig. 2, b), feed it between the cutting edges, directing the upper blade exactly in the middle of the marking line, which should be visible during cutting. Then, squeezing the handle with all fingers of the right hand except for the little finger, perform the cutting.

In Fig. 2, c, d shows the cutting technique with scissors.

Hand scissors, one handle of which is clamped in a vise, are used for straight-line cutting of small thickness metal.

Chair shears are larger than hand shears and are used for cutting sheet metal up to 3 mm thick. The bottom handle is firmly clamped in a bench vice or secured (hammered in) on a table or other rigid base. For cutting sheet metal up to 3 mm thick chair scissors with a stationary fixture are used (fig. 3, в).

Chair scissors are not productive, when working require considerable effort, so they are not used for cutting large batches of sheet metal.

Hand made small-sized power shears. Novator A. Н. Small-size power scissors were designed by Vasiliev to cut sheet steel up to 2.5 mm thick, rods, bolts (studs) up to 8 mm in diameter. These scissors have the same dimensions as standard hand scissors For cutting, the handle is clamped in a vice and the (working) handle is actuated. The working handle is a system of two levers connected in series. The first lever, on one arm of which the blade is mounted, is connected to the handle with a screw.

Second arm of the lever, which is the handle in standard scissors, is made shortened and ends with a hinge, or the scissor handle itself. The handle is connected to the handle by an end hinge by means of a double-hinge link. This lever system increases the cutting force to about twice that of conventional scissors of the same size. The scissor blades are interchangeable and are bolted to the arms with countersunk rivets.

This shear is also equipped with a product for cutting bars up to 8 mm in diameter. The device has discs with holes fixed on the levers of scissors and represents usual scissors, but with specially shaped blades (hardened hubs). These blades are interchangeable and are inserted in the disc socket. For bolt (saw-tooth) trimming. one of the discs has a sleeve (several threads) that protects the threads of the bolts when machining.Cutting edges are sharp at 75° to 85° and prevent from crushing.

HVAC How to Cut Sheet Metal

Small-sized power scissors offer a good cut quality.

Lever scissors are used to cut sheet steel up to 4 mm thick, aluminum and brass up to 6 mm. Upper hinged blade is lever operated. Bottom blade. rigid.

Blades are made of steel U8 and hardened up to hardness HR.C 52. 60. Angles of sharpening of cutting edges 75° to 85°.

Before working, check if the rubbing parts are lubricated, if the lever moves smoothly, if there is no gap between the cutting edges.

When cutting the metal the right hand grasp the lever handle and smoothly move it to the upper position, while the upper knife 3 goes up. Then lay the sheet so that the left hand holds it horizontally and the cutting line is in sight and coincides with the blade of the upper blade. Use your hand to lower the lever with the blade downward until part of the metal is cut through, then move the lever to the upper position. Then the sheet 4 is lifted slightly with the left hand, moved along the cutting edge of the upper knife and repeated the cutting method until a full cut is achieved. The scissors provide a cut without indentations, edge cuts and sufficient accuracy.

Hand scissors are widely used for cutting sheet metal of thickness 1,5. 2,5 mm with tensile strength 450. 500 MPa (45. 50 kgf/mm2) (steel, duralumin, etc.). д.). Use these scissors to cut metal of considerable length. The lever scissors have a cast iron base and table, the lower fixed blade is built into the table, the upper moving blade with a curved cutting edge is mounted in a knife holder. The upper movable knife has a counterweight that balances the knife holder with the knife.

Set the size of cut-off pieces to the required distance from the cutting edge of the lower fixed blade by setting a pre-marking or adjusting the stop to the required cutting edge. While cutting, the sheet is pressed tightly by its lateral edge to the stop and the other edge to the spring stop. After that, turning the handle away from yourself the sheet is pressed tightly on top of the pressure bar and lowering the upper nose with a knife-holder 6, cut the workpiece.

The knife holder rests on a spring-loaded stop when lowered. The stop is set by means of a handle.

Shears with diagonal blades (guillotine) allow to cut sheet metal with thickness up to 32 mm, sheets with dimensions of 1000-3200 mm, less often. strips, as well as nonmetallic sheet materials.

Pereosnastka.ru

Metal cutting with hand scissors is widespread in metalwork and tinsmithing shops. You can use the scissors to cut through very thin sheet metal and strips, and complex structural shapes.

Cutting of sheet and strip metal with scissors is performed without removing chips. by shearing. The essence of the shear cutting process is the separation of a part of the metal under pressure of a pair of cutting knives along the shear line of their direction.

Aviation Snips Basics. when you need to cut or trim sheet metal

in the process of cutting, the sheet to be cut is placed between the blades. The upper blade pushes the sheet against the lower blade as it descends. Both blades press into the sheet metal surface and then separate it through the resulting shear cracks. Angle of sharpening p of the cutting part of the scissors varies from 65° to 80°, depending on hardness of the cut metal; for soft metals (copper etc.) it’s 65°, for metals of medium hardness. 70-75°, for hard metals. 80°. In order to decrease friction of the blade during the operation, rear angle a of 2-3° is created on its cutting surfaces.

In order to obtain a clean cut, the gap m between the upper and lower knives must be correctly set. If the gap is small, the direction of cleavage cracks does not coincide with the direction of the cut, and its surface will be rough, “torn”. With a large gap, the cutting surface will have a large burr.

The size of the gap between the knives depends on the thickness of the cut metal, but should not be more than 0,5 mm. In manual shears this gap usually does not exceed 0,1-0,2 mm.

In order to decrease cutting effort the cutting blades are set at an angle Ф one to another. The larger this angle, the lower the cutting force. However, a large angle of inclination of the blade increases its travel and creates a force that pushes the sheet out from under the blades. Guided by these considerations, angle f is taken equal to 7°-12°.

Depending on the device of the cutting blades (blades), hand scissors are divided into straight scissors. with straight cutting blades, designed mainly to cut material in a straight line and around a large radius; curved scissors. with curved cutting blades and finger scissors. with thin and narrow cutting blades, used to cut holes and surfaces with small radiuses in sheet material.

Hand scissors are subdivided into right- and left-handed according to cutting blades location. Right-handed scissors have the bevel of the lower blade on the right-hand side, and left-handed scissors have the bevel of the lower blade on the left-hand side.

Hand shears are made of carbon steel tool grade U7. Blades of scissors are quenched and then tempered to hardness of HRC 52-60. Cutting edges of scissors must be straight, without cracks and blockages. The length of the cutting blades up to the rotation axis is usually from 55 to ПО mm, the total length of the scissors is from 200 to 400 mm. The most popular are scissors with the length of 250-320 mm.

Metal cutting with a hand scissor.

When cutting manually, the scissors are held with the right hand. Thumb is placed on the upper handle of scissors, and index, middle and ring fingers grip the lower handle. The little finger must be between the handles, and while cutting, it is used to move the scissors apart. Some locksmiths prefer to do this with the index finger, but this method is not quite convenient. Use your left hand to feed the sheet, lifting it slightly to make it easier for the scissors to move.

See also  What oil in the engine of the walk -behind tractor. Why car engine oil is not suitable?

In the process of cutting you should not open the scissor blades to a large angle, because with a large opening of the blade will push out, but not cut the metal. Scissor blades should be open for about 2/3 of their length.

To prevent notches and burrs when moving scissor blades forward along the marking line, it is necessary that the planes of blades pressed to the cutting plane and follow the marking. The cutting edges of the blades must be well sharpened, and the cutting surfaces (planes) must be properly adjusted and fixed on the axis. Scissors are usually checked by paper cutting: well sharpened and adjusted scissors must cut paper. Cut the marked sheet so that the marking line is in the line of sight. Therefore, cutting sheet metal in a straight line of mowing line and in a curve (circles and roundings) without sharp turns is done with the right scissors.

Cutting a sheet along a curved contour or cutting circular disks is most convenient with scissors with curved cutting blades. When cutting out holes and curved inner contours it is necessary to chisel a hole in the material for the shear blades to pass through, and then cut along the line. For cutting holes it is better to use finger scissors.

Quality of the cut depends on the correct positioning of the piece relative to the cutting edges of the scissors. There must be a right angle between the cutting plane and the workpiece, otherwise the scissors will spring and jam the workpiece, an indentation will appear on the workpiece, and it will be much harder to cut it. Hand scissors can cut sheet and strip steel up to 0,3 mm thick, roofing iron up to 1 mm thick, copper and brass sheets up to 2 mm thick.

Cutting metal with lever scissors. Manual cutting of metal is also performed on lever scissors: chair, flywheel, toothed rail (sectional) and other types.

Chair scissors, unlike hand scissors, are made in large sizes. They have one bent handle with pointed end for fastening to a thick board or workbench, and the second one, extended. for hand work. Chair shears are stable in operation and give considerable freedom to the hands of the mechanic. They are used for cutting sheets with a thickness of 2-3 mm.

Lever-arm shears consist of vertical cast-iron uprights and a mounted shear bar.They have a metal table on them. In the right longitudinal lateral plane of the table the lower cutting knife is fixed the upper knife is mounted on the flywheel, seated on the axle. In order to prevent the flywheel self- lowering a counterweight is mounted on its tail part.

Cutting sheet metal on the lever-arm scissors of I-37 type can be performed by the marking and the stop. To cut a sheet according to the marking, lay it on the table so that the marking risk coincides with the blade of the lower knife. Then, when the sheet is pressed by the clamping plate, the lever with the upper knife is lowered with a force and “pressed down” until the required part of the sheet is cut. When cutting sheets by the stop (without marking) the width of the strip to be cut off is adjusted by the movable stop bar.

The sheet length which can be cut with the shears can be quite long, because the shears allow moving the sheet along the blades. Length of cutting blades of this type of shears is 1050 mm, angle of blade slope f=712°, thickness of cut sheet. up to 2.5 mm.

Lever scissors with a toothed rack are used to cut sheet steel up to 3 mm thick, thin rods and small section metal. They consist of a frame in the lower part of which the shear blade is fixed. When the lever is lowered, the force transmitted through the gear change, the shackle and the slide with the blade fixed on it ensures that the metal of the allowed cross-sections is cut.

The movement of the slider with the upper blade is controlled by a hand crank via a toothed gear and a lever.

Lever blade cutters are made of tool steel U8. Knife blades are hardened and then tempered to HRC 52-60. Angle of sharpening of cutting surfaces of knives P = 75-t-80°. Smaller point angle blunts knives more quickly or chipping out, larger point angle makes them stronger but requires more cutting force.

STOP DOING THIS WRONG! How To Use Aviation Snips The RIGHT WAY

Hand scissors of H-911 and HA-913 models are used for cutting section rolled products of round, square, angle, strip, channel and T-joint sections (fig. 4,б). These scissors allow cutting steel of different cross-sections: round. 25 mm in diameter, square. up to 22X22 mm, strip. 550 mm, angle. 65658 mm, and T-beam. 355 mm.

Cutting metal with electric and pneumatic shears. To mechanize the relatively heavy and time-consuming process of cutting sheet metal with scissors, electric and pneumatic scissors are used. With these scissors, straight and curved cuts with a smallest radius of curvature of about 20 mm can easily be made with the help of a template, which also greatly increases the cutting performance.

Domestic industry produces several sizes of electric shears. For example, electric shears brand I-31 are designed for cutting sheet steel up to 2.7 mm thick. They consist of a housing in which a 370 W electric motor is installed, and a blade head housing. The motor anchor turns the eccentric roller by means of a worm pair. The crank arm is seated with the upper head on this roller, and the lower head is connected to the upper blade lever pin. Bottom blade attaches to the bracket.

In the process of work the crank, making reciprocating motion and forcing the upper knife arm to swing, produces metal cutting. The clearance between the knives is set by moving a bracket in the knife head’s crankcase. The gap is set according to the thickness of the metal to be cut. The circular saw blades can be suspended or supported by the top handle for easy operation. Productivity of electric shears of I-31 brand up to 3 m/min.

At Kolomna Textile Machinery Plant on the proposal of G. Е. Electromagnetic vibrating hand shears for cutting thin metal sheets with thickness of 0,5-1,5 mm were designed and put into production at Morgunov Institute of Textile Machinery. The scissors is an electromagnet with a coil and an armature mounted inside the body on the base. Fixed shear is attached to the same base and movable shear is attached to the axis. The right arm of the knife is attached to the electromagnet armature with a shackle. A spring presses the knives one against the other.

Blades are made of U8A steel. Electromagnetic shears work on the principle of regular shears. They are light, compact and easy to work with.

Electromagnetic scissors of VEN model are used for cutting cardboard gaskets.0 design Jl. М. Sytykh and V. А. Ovchinnikova. Their principle of operation is similar to that considered above. A fixed knife is attached to the coil core and a moving knife to the vibrating armature. The shears are actuated by pushing on the switch. Variation of cutting speed is controlled by a screw. The shears are plugged into a 220 V mains supply, and if the coil is designed for 36 V, they are connected via a transformer.

The shears have a high cutting speed (up to 3 m/min) and weigh 350 g. Short cutting length (3 mm) in one stroke makes them suitable for cutting gaskets of complex configuration.

Pneumatic scissors are designed to cut sheets up to 1.5 mm thick. They have small dimensions and weight (1.5 kg), so they are easy to use for metalwork and assembly work and in all cases where the stationary scissors cannot be used.

Presentation “Basic methods of cutting thin sheet metal and wire” 5th grade

After you share the material below you will see a link to download.

Slide captions:

questions 1. Types of metal and wire cutting tools. 2. Types of scissors and how they differ. 3. Using ratchet scissors. 4. Pliers, their construction and principle of operation. 5. Industrial metal and wire cutting devices. Types of metal and wire cutting tools 1. Locksmith shears are used for cutting sheet metal. 2. Wire cutting Pliers are used for cutting wire. Types of scissors Scissors are differentiated by the shape of the blade. 1. Straight 2. Curves Use of scissors Sheet metal cutting with scissors can be performed directly on the workbench table manually (Fig. a) and a vice (fig. б). When cutting, the blade is guided precisely along the line, and the workpiece is lifted slightly and pressed against the scissors. Pliers, their construction and principle of operation.

Wire cutters are used to cut steel, copper or aluminium wires up to a diameter of 3 mm. Pliers have handles and jaws. Blades of the jaws move towards each other and cut the wire.

Industrial metal and wire cutting devices.

  • Factories use mechanical shears for cutting sheet metal and large-diameter rods. They come in guillotine and circular shears.
  • The process of cutting with guillotine shears is the same as with hand shears.
  • Circular shears cut sheet metal with the sharp edges of rotating discs.

Safety measures when working with scissors

Always wear gloves on the hand holding the workpiece. 2. Securely clamp the locksmith scissors in a vise. 3. Keep your left hand away from the scissors and cutters to keep your fingers away from the blade. 4. Handle the scissors and wire cutters with the handles away from you and place them on the table with the handles toward you. 5. When you cut a small piece of wire with the wire cutters, point the wire cut off in the direction of the workbench shield.

Cutting metal with hand shears

Metal cutting with hand scissors is often used in metalwork and tinsmithing. With the help of scissors it is possible to cut very thin sheet and strip material, and also workpieces of complex configuration.

Cutting sheet and strip metal with scissors is done without removing chips. by shearing. The essence of the process of cutting by shearing consists in the separation of a part of the metal under the pressure of a pair of cutting blades on the mowing line of their direction.

In the process of cutting a sheet 2 (fig. 67,

A) is placed between knives 1 and 3. the upper blade, lowering, presses down on the metal, pressing it against the lower blade. Both knives press the surface of the metal and then separate it with shear cracks. Angle of sharpening (3) of the cutting part of the scissors varies from 65° to 80° depending on hardness of the metal being cut: for soft metals (copper, etc.) and for soft metals (cobalt, etc.) the angle of sharpening (3) varies from 65° to 80°.) it is equal to 65° for metals of medium hardness 70-75°, for hard metals 80° In order to reduce friction of knives in the process of work on their cutting surfaces is created rear angle a, equal to 2-3°.

To get a clean cut, it is necessary to choose the right gap t between the upper and lower blades (Fig. 67, б).

If the gap is too small, the direction of shear cracks does not coincide with the direction of shear, and its surface will be rough, “torn. With a big gap the surface of cut will have big burrs. The size of the gap between the knives depends on the thickness of the cut metal, but must not be more than 0.5 mm. In manual shears this gap usually does not exceed 0,1-0,2 mm.

In order to decrease power consumed when cutting, cutting blades are installed at an angle Ф one to another (fig. 67, а). The greater this angle, the lower the cutting force. However, a large angle of the blade increases its stroke and creates a force that pushes the sheet out from under the blades. For this reason, angle f is taken equal to 7°-12°

Depending on the cutting blades device, hand scissors are subdivided into straight scissors (fig. 68, o). with straight cutting blades, ttredesignated mainly for cutting material in straight mowing line and in circumference of big radius, curved scissors

With thin and narrow cutting blades (Fig. 68, d), used for cutting holes and surfaces with small radii in sheet material.

Hand scissors are divided into right-hand and left-hand shears according to the location of the cutting blades. The bevel of right-handed shears has the lower blade cutting edge on the right side, and on the left-handed ones. on the left side.

Hand shears are made of carbon steel tool grade U7. Scissor blades are hardened, then tempered to hardness NNC 52-60. Cutting edges of the scissors must be straight, without cracks and blockages.

Length of cutting blades up to the rotation axis is usually from 55 to 110 mm, the total length of the scissor blades

From 200 to 400 mm. The most used scissors are 250-320 mm long.

How to cut metal with hand scissors.

When cutting manually, the scissors are held with the right hand. The thumb is placed on the top handle of the scissors (fig. 69, a), and the index, middle, and ring fingers grasp the lower handle. The little finger must be between the handles: it is used to extend the shears during cutting. Some locksmiths prefer to do it with the index finger (fig. 69, b), but this method is not quite convenient. Use your left hand to feed the sheet, lifting it slightly to make it easier for the scissors to move.

While cutting, you should not open the scissor blades at a large angle, because with a large opening of the blades will push out, but not cut the metal. The scissor blades should be opened to about 2/z of their length.

See also  Tools and equipment for installation work

In order to prevent notches and burrs when moving the scissor blades forward with the marking line it is necessary that the planes of the blades press against the plane of the cut and follow the marking. Cutting edges of the blades must be well sharpened, and cutting surfaces (planes) must be correctly adjusted and fixed on the axis. Scissors are usually checked by cutting paper: well sharpened and adjusted scissors must cut paper. Cut a marked sheet so that the marking line is in the field of view. That’s why cutting sheet metal in a straight line

Cutting along curves (circles and curves) without sharp turns is done with the right scissors

It is more convenient to cut a sheet along a curvilinear contour or to cut circular disks with scissors with curvilinear cutting blades. When cutting out holes and curved inner contours it’s necessary to chisel a hole in the material for the scissor blades to pass through, and then cut along the cutting line (fig. 70, в). To cut holes, it is best to use a pair of pin scissors.

Cutting quality depends on the correct positioning of the workpiece relative to the cutting edges of the shears. There should be a right angle between the cutting plane and the workpiece, otherwise the scissors will spring and jam the workpiece. A dent will appear on the workpiece and it will be much more difficult to cut it.

Hand scissors can cut sheet and strip steel up to 0,8 mm thick, roofing iron up to 1 mm thick, copper and brass sheets up to 2 mm thick.

Cutting metal with lever scissors. Manual metal cutting is also performed on lever scissors: chair scissors, flywheel scissors, toothed rail scissors and other types.

Chair scissors unlike hand scissors are made in larger sizes. They have a single curved handle with a sharpened end for fastening to a thick board or workbench (fig. 71, a), and the second one, elongated. for hand work. Chair scissors are stable in operation and give considerable freedom to the hands of the mechanic. sheets with a thickness of 2-3 mm can be cut with these.

Lever-arm shears consist of vertical cast-iron legs 7 (fig. 71, b) and metal table 2 mounted on them. At the right pro-

Lateral lateral plane of the table is fixed lower cutting knife 9] upper knife 5 is installed on the flywheel 4, planted on the axis 7. To prevent self-lowering of the upper arm, a counterweight 6 is installed at its tail part.

Cutting of sheet metal on the lever-arm shears of this type can be performed by the marking and stop. For cutting by marking, a sheet is arranged on the table in such a way that the marking risk coincides with the blade of the lower blade. Then the sheet is pressed by the presser plate 3, the arm with the upper knife is lowered with a strong movement and “pressed down” until the required part of the sheet is cut off. When cutting sheet by stop (without marking) width of cut strip is regulated by movable stop bar 8.

The length of the sheet metal to be cut with the scissors can be quite long, because the scissors allow movement of the sheet along the blades. Length of cutting blades of this type of scissors is 1050 mm, angle of blade p=7-12°, thickness of cut sheet is up to 2.5 mm.

Lever scissor blades are made of tool steel U8. Blades of knives are hardened, then tempered to hardness of НЯС 52-60. Angle of sharpening of cutting edges f = 75. т. 85° Cutting surfaces with a smaller sharpening angle dull or chipped more quickly, those with a larger sharpening angle are more durable, but require more cutting power.

Metal cutting with hand tools and on machine tools

As you know, metals can be cut with hand tools and machines.

Depending on the material and size of the workpiece, a distinction is made between cutting metals without chip removal (shearing) with scissors, wire cutters, and with chip removal.

a cutting; b curved cutting; c cutting; d hole cutting.

All other methods associated with removal of metal layer (chopping, filing, cutting with a hacksaw, drilling, turning, milling, planing), performed both with hand tools and on machines, are cutting with chip removal.

  • What are some ways of cutting metal?
  • What kinds of work can be done with hand scissors?
  • What kind of tools are used for cutting with chip removal??

Cutting sheet metal with hand shears

Cut sheet metal into separate parts, cut holes in the parts, produce parts with curved contours and perform other similar work can be performed with hand shears. Depending on location of cutting edge of scissor blades (on the right or on the left from lower blade) they are called right-handed scissors (fig. 47, a) or left-handed (fig. 47, б). Hand scissors are made with straight lines (Fig. 47, a, b) and curved (fig. 47, c) cutting blades.

Hand scissors with straight cutting blades are applied for cutting of steel sheets, strips and bands with thickness up to 0,7 mm, and of non-ferrous metals up to 1,5 mm along straight lines. Scissors with curved cutting blades are used when cutting sheets, strips and bands of steel up to 0.6 mm thick, and of non-ferrous metals up to 1.2 mm thick along curved lines or when cutting parts with a combination of curved and straight lines.

GOST 7210-54 manual scissors are made in lengths of 200, 250, 320 and 400 mm, in which case the width of the outer edge of the handles in closed position is 40, 40, 50, 55 mm.

Scissors consist of two halves, which are manufactured as one-piece or compound with the blades welded together. Solid halves of scissors are made of carbon steel 65, 70. Handles of welded scissors are made of carbon steel of Sta grade and above. 2, and blades. from tool carbon steel U7 with heat treating them to hardness HRC 52-58. Cutting edges of blades are sharpened at angle of 70-75° (fig. 47,(3). There shall be no chips, tears, burrs, burrs, cavities, lacerations, hairs, nicks or cracks on the blades or surfaces of the scissors.

Blades of scissors in closed state must overlap each other, and overlap on the ends must not exceed 2 mm. The two halves should be connected with a screw and nut and ensure a tight fit of the halves without tilting or backlash. the scissors must cut with any part of the cutting edges; they must move smoothly without jerking.

In Fig. 47, d shows hand scissors with a different blade shape from conventional scissors. Lower blade is straight upper blade is curved in the direction of the cutting edge. Bottom blade has a special flange, thanks to which the cut part of the sheet is deflected and the scissors freely move along the mowing line of the marking along the whole cut sheet. This shape of the blades allows these scissors to cut with less force. These scissors have handles angled 30° to the cutting plane, which eliminates the possibility of cutting your hands. They cut through sheet metal in half the time it takes to cut through it with these scissors compared to standard hand scissors.

Plates are cut with hand scissors, as a rule, along the marking lines marked on the surface of the plate in advance.

When cutting sheets into wide strips, unbend the strip to be cut with the left hand, without making any sharp bends (fig. 48, а). This will make it easier for the scissors to move while cutting and protect your right hand from being cut.

When cutting a sheet with left-handed scissors (fig. 48, b) on narrow workpieces make sure they bend forward.

When cutting sheet metal on a curved contour, e.g. when cutting a circle with left-hand scissors, cut in a clockwise direction, positioning the scissors so that they do not cover the marking with the blade of the mowing line (Fig. 48,в).

Parts with curved outline are cut with the right scissors counterclockwise (fig. 48, г).

When cutting, open the scissors to about 2/3 of the length of the blades, so that they well grasped and cut the metal without much effort. Strongly opened blades do not cut, but push the metal out.

It is necessary to keep the cutting plane perpendicular to the sheet to be cut, because tilting of the scissors leads to metal crumpling on the cut edge, jamming and burr forming.

When moving the scissors forward, they are pressed firmly against the end of the cut, otherwise burrs are inevitable. Holes in the parts are cut with cutters with curved cutting blades (fig. 48, д).

METAL CUTTING

Cutting (cutting). an operation to separate parts from a bar or sheet metal. Cutting differs from cutting in that the impact force is replaced by the load of the gouge. This is done in two ways: with or without chip removal. For cutting with stripping chips are used: hand hacksaw, slicing hacksaw, metal saws, metal cutting machines (lathes, mills, grinders), autogenous gas cutting, anode mechanical cutting, etc.д. Cutting without removing chips is made with hand, lever and mechanical scissors, wire cutters, pipe cutters, press scissors, parallel (guillotine) shears, dies, etc.д. Cutting is done by hand and by machine.

Handheld hacksaw blades are used for cutting sheets, strips, round and profiled metal, cutting grooves, trimming and contour cutting of work pieces, etc.д.

Manual locksmith’s hacksaw (fig. 7.1) consists of machine (frame) 5, handle 6 and hacksaw blade 3. The blade is inserted with the ends into the slots in the hacksaw blade 2 and stationary 4 heads, then secure with pins and tighten with a thumb nut screw 1. Hacksaw frames are made in one piece (fig. 7.1, a) and sliding (fig. 7.1, б). The former are used to clamp hacksaw blades of one particular length, the latter allow the clamping of hacksaw blades of different lengths.

Hacksaw blade is a narrow hardened steel plate with teeth on one or two ribs and two holes at the edges (Fig. 7.2, а). The length of the handheld hacksaw blade is equal to the distance between the centers of its two holes. According to GOST 6645-86 it is possible to allocate the following basic dimensions of a hacksaw blade: length I, width L, height Ь, pitch Р toothing angle. The most commonly used hacksaw blades for handheld hacksaw length I, Equal to 250 or 300 mm, with a height of Ь, equal to 13 or 16 mm, width /г, equal to 0,65 and 0,8 mm respectively.

Fig. 7.1. Hand-held locksmith’s hacksaws: а. fiduciary (1. wing nut; 2. movable head;

Each tooth of the hacksaw blade has a wedge shape (Fig. 7.2, б) and the following geometry: back angle a, sharpening angle (3, front angle y, cutting angle 5. For the geometry of the hacksaw blade the equations are fulfilled:

When cutting, a chip that looks like a comma is placed between two neighboring teeth until the tip of the tooth leaves the kerf. The size of the chip space depends on the value of the rear angle a, the front angle and the pitch Р. For cutting metals of different hardness the following values of angles are accepted: y= 0. 12 0. а = 35. 40°, Р = 43. 60°. To cut harder materials, blades are used, which have a sharpening angle P more, to cut soft materials. less.

pitch P of the teeth of a hacksaw blade. the distance between two adjacent teeth (fig. 7.2, б). The choice of a hacksaw blade with an appropriate pitch depends on the properties of the metal to be cut. For cutting cast iron, mild steel a blade with a pitch of 1,2. 1,5 mm, profile steel

а. blade construction; б. blade tooth geometry; в. the wiring on the blade; г. 2. Flaring by the tooth; к. cutting width

rolled and pipes, non-ferrous metals. 1,25, thin-walled pipes, thin sections, soft and ductile metals and alloys (brass, copper). 1,0, for sheet steel. at 0,8 mm pitch.

To avoid jamming of the hacksaw blade in the metal, the teeth are set apart. There are two ways to do this: 1) along the blade (wavy cutting) (Fig. 7.2, в), when the blade is bent to form waves with a pitch of 8Р; 2) along the tooth (Fig. 7.2, г). only the teeth are swung apart and the blade is not affected. The setting along the blade is applied for blades with a pitch up to 0,8 mm, the setting along the tooth. for blades with a pitch over 0,8 mm.

Blades are made of steel grades U10A, P9, X6VF with hardness of Sh1S 61. 64.

Before you start cutting metal, it is necessary to choose a hacksaw blade taking into account the hardness, shape and size of the metal to be cut. The hacksaw blade must be installed in the slots in the heads of the hacksaw so that the teeth are pointing with the tip away from the handle (see Pic. Figure. 7.1, а). The first end of the blade is then inserted into the fixed head until the holes match and the position is secured by inserting the pin. Then insert the second end of the blade into the slit of the mobile head and fix it with the second pin. Tension the blade by turning the wing nut (fig. 7.3, а). It should be borne in mind that a tightly stretched blade can tear with a slight twist, and a weakly stretched one will bend and break in the process of cutting.

Fig. 7.3. Techniques for working with a locksmith’s hacksaw: а. tensioning the hacksaw blade; б. right hand position; в. left hand position; г. cutting into the rolled rectangular section; д. plunge cut into the round bar; е. cutting thin sheet metal

Then the workpiece is marked out and firmly clamped in the vice. The height of the vice must correspond to the height of the worker (Fig. 7.4, а). Standing when cutting is half-turned to the vice, i.e.е.

See also  Tool for bending metal with their own hands

at an angle of 45° to the longitudinal axis of the vice (fig. 7.4, б). The distance between the vice and the user’s body must be

  • 200300 mm. Stand straight, freely and steadily in front of the vice. Left leg must be put forward and lean the body on it. The feet are placed so that they form an angle
  • 6070°. Worker’s posture is considered correct if between shoulder and elbow parts of his right arm bent at the elbow with the hacksaw placed on the jaws of the vice a right angle is formed (Fig. 7.4, а).

Fig. 7.4. Position when working with a hacksaw: а. hacksaw body and hacksaw; б. legs (feet)

The handle of the hacksaw is embraced with four fingers of the right hand, with the end of the handle resting in the middle of the palm, and the thumb is placed along the handle (see. Fig. 7.3, б). Hold the frame of the hacksaw with the left hand so that the thumb is inside the frame and the other hand grips the tensioning screw of the sliding head (see Pic. fig. 7.3, в). To facilitate plunge cuts, the hacksaw is tilted toward the back edge of the workpiece (see “7.a”). Fig. 7.3, г) or place a metal stop at the place of the cut and rest the blade of the hacksaw against it (see 3. fig. 7.3, д). In some cases a shallow cut is made at the place of the future cut with a triangular file to guide the hacksaw better. When cutting, you must coordinate the efforts of your right and left hands. The movement of the hacksaw must be absolutely horizontal. Press on the hacksaw with both hands, but the greatest effort is made with the left hand, while the right hand performs reciprocating motion of the hacksaw.

The process of cutting consists of two strokes: the working stroke, when the hacksaw moves forward from the worker, and the idle, when the hacksaw moves backwards in the direction of the worker. When idling, do not press the hacksaw, but pull it toward you. During the working stroke, both hands press the hacksaw with both hands, providing the cutting force.

The following rules must be observed when working with the hacksaw:

  • The entire blade must be involved in the work;
  • work with the hacksaw should be slow, without jerks, smoothly;
  • Cutting rhythm with a hacksaw is 30. 40 double strokes per minute on hard steel, 40. 50 for medium-hard steel and 50. 60 double strokes per minute for cutting soft steel and non-ferrous alloys;
  • Short workpieces are cut on the widest side;
  • before the end of the cut the pressure on the hacksaw must be relaxed, because if the strong pressure the hacksaw blade can break and cause injury to the worker;
  • The blade should be periodically lubricated with mineral oil or graphite grease;
  • The new blade should cut softer steels and alloys, the blunted blade should cut harder ones;
  • the pressure on the hacksaw depends on the hardness of the metal and the size of the part being cut (hard metals require more pressure than soft ones, narrow parts require less pressure);
  • the workpiece must be securely clamped in a vise;
  • If the blade is “tilted” away from the marking mark, turn the workpiece and start cutting in a new place.

Workpieces with a locksmith’s hacksaw are cut of different profiles and cross-sections. In this case it is necessary to take into account some peculiarities of cutting these workpieces.

  • 1. Strip material is cut on a narrow plane if its thickness ensures simultaneous work of at least three teeth. Therefore thin strip material is cut as follows: a) along the wide edge; b) along the narrow edge, when the workpiece is clamped between two wooden blocks (see Pic. fig. 7.3, е); c) along a narrow edge by gathering several identical workpieces together (a batch). These methods of cutting narrow workpieces exclude blade teeth pitting.
  • 2. Round, square, and hexagonal bars are cut with the hacksaw horizontal, but so that the blade does not meet sharp corners when moving. Such bars are usually notched on two or four sides.
  • 3. when cutting rather wide surfaces it is necessary to tilt the hacksaw blade alternately to the back and to the front edge of the workpiece. This method of cutting does not cut across the whole width of the cut and makes the job easier.
  • 4. With long or deep cuts, when it is not possible to complete the cut because the frame of the hacksaw rests on the edge of the workpiece and prevents further cutting (Fig. 7.5, а), necessary to turn the blade in the frame by 90° (Fig. 7.5, б).

Fig. 7.5. Cutting with a hacksaw for deep cuts: а. the frame rests on the workpiece; б. Cutting with a 90° turn of the blade; в. closed loop operation

When cutting workpieces with closed rectilinear contour (fig. 7.5, c) they are also cut with the blade turned through 90°. Before cutting, drill apertures in the billet with a diameter equal to the width of the blade at the crossing points of the future cuts, and, having passed the blade through the holes, fix it in the frame and cut according to the markings.

When cutting workpieces with a curved contour, jigsaws are used (Fig. 7.6, а).

Fig. 7.6. Cutting techniques: а. With the jigsaw blade; б. Cutting pipe with a hacksaw; в. Cutting slits

  • 7. A pipe is cut according to the marks by clamping it in a parallel vice. Thin-walled and clean-surfaced pipes are cut by clamping them in a vice between two wooden bars (fig. 7.6, б). When cutting, you should periodically turn the pipe. Cut with very light pressure without tilting the blade away from the marking mark. If the hacksaw “moves” away from the marking, turn the pipe and start cutting in a new place.
  • 8. Before you start cutting the metal of shaped section, for example, angular section, it is necessary with the help of an angle piece and a diecutter to make marks in the places of cutting on both flanges (when you cut a channel, the risk should be put and on its wall). After that, cut metal clamped in a vice so that were visible risks of both flanges, and three-sided file make a small cut on the edge of the risk with the corner of the base of the profile. After setting the hacksaw blade into the kerf, start cutting the profile, holding the hacksaw in an inclined position, and then level it and cut horizontally. When cutting blanks with a hacksaw of different profiles, it is necessary at all times to monitor its direction, not allowing to deviate from the marked risk.

The hacksaw can be used to make cuts in the heads of screws (Fig. 7.6, в). Make wide slits with two blades folded together.

MANUAL AND MECHANICAL CUTTING

(object) into two separate pieces using hand scissors, a chisel, or special mechanical shears. Sawing is the operation of separating material (an object) using a hand or mechanical hacksaw or circular saw.

Name tools for cutting and sawing material.

The simplest tool for cutting metal is an ordinary right and left hand scissors (the upper cutting edge is to the right or left of the lower cutting edge). They can be handheld Fig. 17. Hand saws and stationary, fixed. for cutting metal, mounted on a workbench. Mechanical devices and equipment include vibrating shears and machines, lever-operated mechanical shears,” and guillotine shears and presses. Cutting sheet material, especially cutting out shaped parts, is done with an acetylene-oxygen gas torch, and in some cases with finger and other special cutters on milling machines. Bar material can be cut on lathes with cutoff cutters. Pipes are cut with special pipe cutters. Hand and mechanical hacksaws with a permanent or sliding frame, band saws, circular saws, and other mechanisms are used to cut materials.

Name the main parts that make up a hand hacksaw.

A manual hacksaw consists of a fixed or adjustable frame, a handle, and a hacksaw blade. The blade is attached to the frame with two steel pins, a bolt and a wing nut. A bolt and nut is used to tension the blade in the frame

What is a hacksaw blade and what is its purpose? 47

Hacksaw blades are thin, hardened steel strips, 0.6 to 0.8 mm thick, 12 to 15 mm wide, 250 to 300 mm long, with teeth cut along one or both edges.

Hacksaw blades are 1,2-2,5 mm thick, 25-45 mm wide and 350-600 mm long.

Teeth of the blade are characterized by the following angles: for manual hacksaw blades the anterior angle u = 0°, the posterior angle a = 40. 45°, pitch. 0,8 mm, teeth pitch width. 1,2. 1,5 mm;

For hacksaw blades, the rake angle 7 = 0. 50, back angle a = 35. 40°, tooth sharpening angle

§ = 50. 55°, tooth pitch. 2. 6 mm. Teeth can be wavy and bifurcated. Soft metals and imitation materials can be sawn with a hacksaw with a coarse tooth pitch, hard and thin materials with fine teeth.

Blades are made of high-carbon tool steel U10, U12, U10A U12A, for critical work. from steel R9, X6VF, X12F1, tungsten and chrome. After teeth cutting the blade is hardened completely or partially (only the teeth) up to hardness HRC 60-61. The working length of the blade is about 2/3 of its length. Each tooth of a hacksaw blade is a planer

What operation does the mechanic perform before he begins to cut and saw the material??

before sawing or cutting material, the sawmaker should prepare the material, mark it with a scribe or mark it with a tapping block. 43

110 What can cause a blade to crack or break?

Cracked or broken blades can be caused by misalignment of the hacksaw during the sawing process that puts a lot of stress on the flexing of the blade.

What to do with the blade if the teeth break?

If one or more teeth on the blade are broken, stop sawing, remove the blade from the frame and grind away the broken teeth, then the blade can be used again.

Large-diameter pipes must always be sawed with a gradual turn of the pipe, otherwise the tines may break. Thin pipes must be clamped in a vise or fixture with a slight clamping force on the radius, otherwise the pipe may be crushed. Blade with unhardened, sharp, small tooth pitch should be used to cut pipe. Do not insert a new blade where the old blade is cracked or has chipped teeth.

113 What to do when sawing material if the saw blade is at an angle to the surface, or if the blade slides on the material?

If the cutting line is angled to the metal surface, you should stop sawing from this side and start from the other side. To avoid slipping of the blade on the surface

For the material, make an initial cut with a three-edged file.

What tool is used to cut hard materials and why?

Hard materials are usually sawn using mechanical frame, band, or circular saws. Hand sawing these materials is very time consuming and sometimes impossible. Mechanical sawing produces a straight cut.

What is the thickness of a sheet cut with different shears?

Hand scissors are used for cutting tinplate and iron sheet up to 1 mm thick as well as for cutting wire. Leaf material up to 5 mm thick is cut on a pair of lever scissors, and material over 5 mm thick. on mechanical scissors. Before starting to cut, the cutting edges should be oiled.

What should be the sharpening angle of hand scissors?

The sharpening angle of the cutting parts of the shears depends on the material to be cut

The nature and grades of the metal and material being cut. The smaller this angle, the easier the cutting edges of the scissor cutters cut into the material and vice versa. But with a small sharpening angle, the cutting edges are quickly chipped. That’s why in practice the sharpening angle is between 75° and 85°. Sharpen blunt scissor edges on a grinder. Correct sharpening and setting between the edges is checked by cutting the paper.

What else, besides familiar tools and equipment, can be used to cut the material?

In addition to the tools and equipment we know, you can use an oxygen. acetylene flame, with a special torch for cutting.

What is a pipe cutter and how to use it?

The pipe cutter is a tool for cutting pipes

Pipe cutters come in many varieties; single-, double- and triple-blade, as well as chain. р

In the pipe cutter the cutting part is a roller with ground edges. The three-blade pipe cutter consists of a chuck that accommodates two rollers, a cage that accommodates one roller, a handle and levers. The pipe clamped in a vice or a clamping device is put on the pipe and tightened to the stop by means of the handle. The oscillating or rotating movement of the lever and the gradual coming together of the rollers cuts the pipe. A uniform and clean line cut into the pipe can be made with the pipe cutter.

What are the safety precautions when cutting and sawing material??

For safety reasons, you should first check the tool. Then the material must be properly and firmly clamped in a vice or fixture, and the right-

Rice, 20. Knife type pipe cutters (roller cutters): a. three-blade type; b- with one blade and two rollers.

to set the handle of the frame saw firmly and forcibly. Dangerous places near the mechanical scissors are covered with guards or shields. Mechanical scissors are operated according to the instruction manual by a specially trained worker.

| Denial of responsibility | Contacts |RSS