screws

Riveting, tightening of rivets and screws

Riveting

 
Riveting is the connection of an object, which makes it relatively soft and easily machined rivets fasten into pre-drilled work subject. We can say that this connection is similar to the connection of nails and tree. It is more complex as metal is harder than wood.
 
Rivets are cylindrical metal elements with a head that can be in the shape of a hemisphere, lens, conical-recessed or flatnata. They are produced from aluminum and copper.
 
When riveting, the following are used: hammer, tensioner, punch, riveter, a cutter, as well as a spiral drill for drilling holes, and for sheet metal Cornish. In the first stage of work, we mark the workpieces (plates or strips) then we drill them and place them on the riveting workbench. The riveting table can be larger, made of solid steel, with made indentations, which correspond to the head of the rivet. We pull the rivets from below through the pre-drilled sheet metalve that are connected and thus we place the workpiece on the metal plate. The head of the rivet should rest on the bottom of the recess metal table tops. After this we put on the tubular tensioner on the standing end of the rivet and with hammer blows we tighten the working ones items that are assembled in this way (picture 1).
 
riveting
PICTURE 1
 
The next move is to rivet the stem, going around with a hammer into a circle, we shape it, tearing it into another hemispherical shape the head. In this, we are helped by a shaper that indents with its ownwith them, he shapes the split ends of the collar in different wayslike this in almost the same form.
 
A rivet with a countersunk conical head is used if the head of the rivet should not be above the surface betweenroom-bound work pieces. It is not enough to just pierce opening. It is necessary to make a pro on both sides of the openingspreading in the shape of a funnel, slightly larger than the diameter of the trunk rivet cover (conical reamer or spiral drill with a smaller blade angle). The rivet head will now go into the leftcaste expansion. Standing body slamming with a locksmith's hammer we simply push it into the funnel expansion until well close the metal surface. New rivet head, shaped hammer blows, it will be good if the length of the visible body is 1,2-1,5 times larger than its diameter. If the rivet is short, it does not bind, while the longer rivet makes riveting more difficult. Diameter the holes drilled for the body of the rivet should be precisely adjusted its diameter. If possible, we use a drill of the same diameter, because it normally drills a larger hole.
 
"Disassembly" or removal gives us a lot of trouble it rivets. If the rivet head is bulging, we can do it remove with a file and punch out the rivet on the opposite side side. When the rivet head is large, let's try the cutter pull from the side, between the head and the plate and cut the head off the body rivet. We can't do rivets with the head down on this one way to remove. In such a case, the lowered head forremove the pin, in the funnel-shaped recess, with the appropriate one with a spiral drill, and knock out the rivet with hammer blows in the opposite direction (picture 2).
 
disassembly of rivets
PICTURE 2
 
It happens that we have needs not for solid but for laI deal with joining with rivets (e.g. when attaching katabs on one dial). In this case, we use a rivet with a smaller diameter than the opening and we place a flat one a mat under the head. It is a well-known rule: One a rivet is not a rivet. In order to have a strong, not a loose connection, we will use at least two rivets. If, when hitting with a hammer on the rivet, we hear a thud sound, we need to know that his tree broke. If they move assembled workpieces, one to another, that is a sign that we are not tighten the rivets sufficiently or compress the ends well. Need to know that the rivets are standardized. Cold rivets have a diameter from 1 to 37 mm, with a length of 1,5 to 8 diameters. It's strong important to use a rivet of the appropriate size, because otherwise, even a qualified worker will not be able to do his job easily.
 
Tubular rivets are also used (especially in engineering telecommunications as well as in the industry of handbags and decorative galanterial goods). The shank and head of these rivets are hollow, so we will not form the heads by pressing with a hammer, but with a special one tool.
 

Tightening rivets

 
A new way of riveting is the tightening of the rivetsThe advantage is that the head of the tensioner's tree is used for fixing and pritensioning in order to form the rim of the tubular rivet. Tree the tensioner is torn off above the tension limit. Rivet stem tighten the riveting pliers.
 
Rivets are standardized and can be with open or closed ends as well as grooved. For joining thinner ones materials, primarily sheets, open rivets are used, and with materials that must not allow water and air to pass through rivets with closed ends are used. At soft materials and those that crumble (eg wood) are used fromslotted rivets. The rivet head can be semi-round and indulged. Rivet stems that enter the rivet cavities can be with short and long refraction. A rivet head or fits into the hollow rivet bed or pops out. The rivet is from aluminum, copper, mild steel or nickel-copper alloys (monel). The strength of rivets depends on the quality of the material, thickness, type. The shear strength ranges from 60 to 150 cp. We drill the workpieces with a spiral drill bit diameter larger by 0,1-0,2 mm than the diameter of the rivet stem. Body put the fastening rivet into the opening of the riveting pliers, a hollow rivet into the punched hole. Applying pressure with this clamp the handles one to the other with pliers on the workpieceGoy. One tightening is not enough, but you should know that the body the rivet usually breaks on the third tightening. After each one tightening, we put the pliers on the rivet body. The advantage of blind riveting is that the connections are riveted the same, and poor performance is almost impossible. Cover with ofarbath surfaces do not spray during this work. On closed or hard-to-reach places of the work object (e.g. in pipes) to perform the closing head, it is only required a space of 4,8 mm width. The tensioned material does not deform, and not even sheets with a thickness of 0,5 mm. We replace the rivet by drilling the rivets with a drill of the same diameter (picture 3).
 
rivet replacement
PICTURE 3
 

Screws

 
The most widely used connection elements that provide separationconnecting working elements are screws. According toThe types of screws can be: metric, fine, Whitworth and tubular. According to the shape of the head, we distinguish polygonal, furrowed, countersunk, drilled, average screws, etc. This also applies to the nuts-nuts of the screws that we use when the screw is not accepted by the tapped threads of the hole, but by threading the nut on the other end of the smoothly drilled hole. Bolts are usually made of steel, but they are used and screws and nuts made of copper, bronze and aluminum. Susceptible plates under the screw head prevent damage to the surface of the workpiece from the tightened head, they do not allow uncontrolled unscrewing of the screw, as well as loosening, already they transfer the tightening force to a larger surface.
 
Screws with metric threads are mostly used. The angle of the cut threads, the angle of their edges is up to 60°. The diameter of the screw thread is a whole or a tenth of a millimeter, a pitch of the thread (by this we mean displacement byrotation in the direction of the longitudinal axis during one complete revolutionthinner) is also in whole millimeters. Standardized metric screws are given a thread pitch. E.g., M 10 marka nail with a thread diameter of 10 mm with a thread pitch of 1,5 mm (this is also the space between the cuts). A finer thread, which differs from the previous one, it is marked with M 10x1, which means that, unlike ordinary threads, it is more finely toothed, because is the pitch of the thread only 1 mm, i.e. smaller than the previous one.
 
Although less often, Whitworth screws are used threads (e.g. in English-made motor vehicles). They got their name from the name of the first English factory standardized screw threads. The thread diameter is given in English inch, thumb (1"=2,54 mm), as well as the corner at the top of 55°. The angle of inclination of the threads is determined according to the number of threads on the length of one thumb, ie. according to the number of "teeth" on spindle, length 2,54 mm. If the diameter of the thread is not full thumb, let's indicate the same in the form of a fraction. When we come across so thread marking, such as 7/8", then that means yes is the diameter of the screw 22,2 mm, and the number of teeth on one thumb is 9, i.e. the pitch of the thread is 2,8 mm. Whitworth thread, out standard, it is marked with W 3/4x10. This means that the diameter three-quarter inch (19 mm) screw with coarse serrations, 10 serration teeth on one thumb length with a slope of 2,5 mm.
 
The most common application is tubular threads in the execution of tubular installation. They are marked with the letter C, their values ​​are given in inches and coincide with an angle of 55° at the top. Threads are relatively fine, i.e. with a greater number of "teeth". We have to very much make sure that these thumb marks do not represent the diameter of the thread, rather than the inner diameter of the pipe on whose surface the threads are tapped. Referring to the previous example, the label C 7/8" represents such a pipe thread, whose outer diameter is 30,2 m, and 14 teeth are cut into one inch of pipe length with a slope of 1,8 mm.
 
At the free end of the screw, the spindle is threaded by with which the nut is screwed with its threads. Internal the threads of the nut are formed in a pre-drilled hole, a screw threads are formed by tapping on a roller the body. The threads of the nut are slightly wider so that they can be screwed into them screw threads. That is why their diameters differ somewhat. By previously drilling a hole in the material and using a drill for cutting the vine, we make threads in the nut. The diameter of this of the hole is equal to the screw core, and much smaller than the diameter threads. The core is the part of the screw after removalcutting edge. E.g., for metric nut threads, diam 10 mm, we pre-drill a hole of 8,4 mm.
 
External and internal threading is not required some special professional knowledge. It is important that we give the spindle appropriate dimensions of the groove, i.e. the groove of the nut to cut to the prescribed dimensions of the core (picture 4). If the screw is turned clockwise, it is a right hand thread screw. If, on the other hand, a screw, with the same in the direction of rotation, it comes out of the hole, then it is the screw of the left thread, which is marked by a small notch in the corners on the side side of the head, while two more are marked on the head with a notch notches. Such a thread is marked on the drawing with M-10. If it is necessary to fasten the screws, without rough threads, we will perform threads with beginnings in several places. This is marked with 3 M 10x1, which represents spacing 1mm thread, although one turn of the screw lowers by 3 mm. The screw threads are controlled by thread measuring combs. A simpler solution than this is to compare the known screw by placing it next to screw with unknown characteristics. The screws are the same if their notches touch on the entire length of the spindle. The diameter is determined using a template.
 
thread cutting
PICTURE 4
 
Screws are turned with a screwdriver, a key and by hand. To work with a screwdriver, screws with a notch, with a cylinder, are useddric, semi-round and recessed head. Hand in handscrews with a butterfly and slotted head, and screws with hexagonal and square head using spanners. Special screws are supplied with hexagonal recessesoh They are turned using a hexagonal key which is inserted into the thus formed screw head (such is used at MULTIMAKS tool making machines). More and more are in use screws with a cross-shaped notch, which. require the use of a four-blade screwdriver. Nuts are also produced of various shapes (picture 5).
 
types of screws
PICTURE 5
 
We have already said that the wrenches are a must exactly fit the screw head. This also applies to naswivels used when using a slotted screw head. The screwdriver must not be sharp or blunt. Width the length of the blade should be adjusted, and the thickness of the blade the width of the notch. It is possible to turn a screw without a head with a screwdriver, the so-called track bolts.
 
When applying nuts with heads that have a notch (we call them and grooved heads) a special screwdriver is used shaped.
 

Finally, a few ways to work with the screw

 
Steel screws of small dimensions are installed with the help ofdrill bit with magnetized end or key. For our powe need to use a soft wire when screwing in the screw of metal with a looped end. If the screw is brokennuta head, we cut a notch on the screw in which we put fromdrill and remove the screw.
 
During work, we pay special attention not to damage the threads screw. If it does happen, let's try a small arc with a saw to trim the damaged part of the thread. Pretesting screws in order to shorten its height only then when we already put him between the soft jaws of Mengele, yes they would not damage the threads. Steel screws, which are exposed to heatwith human influences, we first spread oil and then screw it in their places. If the screws are rusty, grease the threads with petroleum and after some time the screw head let's hit with a hammer.
 
On screws, which we screw into soft materials, necessarily, let's put a coaster with a large diameter. We should not forget that screw threads do not catch near the screw head unless, we do not cut the thread on the stem to below the head of the screw.

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