Drilling is a cutting process that uses a drill bit to cut a circular cross-section in solid material. The drill bit is usually a rotary cutter, often multi-pointed. Beets are pressed against workpieces and rotated at speeds from hundreds to thousands of revolutions per minute. This forces the cutting edge of the workpiece, cutting the chips (swarf) from the hole when drilled.
In rock drilling, holes are usually not made through circular cutting movements, although few are usually rotated. Instead, a hole is usually made by hammering a drill into a hole with short movements repeated quickly. The hammering action can be done from outside the hole (top hammer drill) or inside the hole (drill down the hole, DTH). The exercises used for horizontal drilling are called drift drills.
In rare cases, special-shaped bits are used for cutting non-circular cross-sectional holes; square cross section is possible.
Video Drilling
Process
The drilled holes are marked with sharp edges on the side of the entrance and the presence of grinding wheels on the exterior side (unless removed). Also, the inside of the hole usually has a helical mark.
Drilling can affect the mechanical properties of the workpiece by creating a low residual stress around the opening opening and a very thin layer of highly stressed and disturbed material on the newly formed surface. This causes the workpiece to become more susceptible to corrosion and crack propagation on the suppressed surface. Final operation can be done to avoid this adverse condition.
For fluted drill bits, any chip is removed through the flute. Chips can form long spirals or small flakes, depending on the material, and process parameters. The type of chip formed can be an indicator of material machinability, with long chips showing good material machinability.
Where possible drilled holes should be located perpendicular to the workpiece surface. This minimizes the tendency of the drill bit to "walk", that is, to be deflected from the center line of the target bore, causing the hole to be misplaced. The higher the length-to-diameter ratio of the drill bit, the greater the tendency to walk. The tendency to walk also takes precedence over other ways, including:
- Setting a mark or a centering feature before drilling, such as by:
- Casting, printing, or forging marks into workpieces
- The punching center
- Drilling (ie, middle milling)
- Place facing, which nails a particular area on casting or forging to make faces that are located accurately on rough surfaces.
- Limit the position of the drill using a drill jig with the drill busing
The final surfaces produced by drilling can range from 32 to 500 microinches. The finished cut will produce a surface near 32 microinches, and roughing will be close to 500 microinches.
Cutting fluids are commonly used to cool the drill bit, increase the life of the chisel, increase the speed and bait, increase the surface finish, and help remove the chip. This fluid application is usually done by flooding the workpiece with a cooler and lubricant or by using a mist spray.
In determining which exercises to use, it is important to consider the tasks and evaluate which exercises work best to accomplish the task. There are different drill styles that each serve a different purpose. Underground exercises are able to drill more than one diameter. Spade drill is used to drill larger hole sizes. Drill indexed is useful in managing chips.
Drilling spaces
The purpose of spot drilling is to drill a hole that will act as a guide to drill the last hole. The hole just drilled part of the path to the workpiece because it is only used to guide the start of the next drilling process.
Drilling center
The drill center is a two-fluted tool consisting of a twisting drill with countersink 60Ã, Â °; used to drill a hole in the center of the countersink in the workpiece to be installed between the centers to rotate or grind.
Drilling hole in
Deep hole drilling is defined as a hole depth greater than ten times the diameter of the hole. This type of hole requires special equipment to maintain straightness and tolerance. Other considerations are roundness and surface finish.
In-hole drilling is generally achieved by some tooling methods, usually drilling pistols or smear smearing. This is distinguished by the cooler entry method (internal or external) and chip removal methods (internal or external). Using methods such as rotating tools and opposite rotary workpieces is a common technique for achieving the required lineage tolerance. Secondary tooling methods include trepanning, skiving and burnishing, tedious drag, or boring bottles. Finally a new type of drilling technology is available to deal with this problem: vibration drilling. This technology breaks the chip with small axial vibrations controlled from the drill. Small chips are easily removed by the drill flutes.
High-tech monitoring systems are used to control power, torque, vibration, and acoustic emissions. Vibration is considered to be a major defect in deep hole drilling which often causes the drill to break. Special cooling is usually used to assist in this type of drilling.
Drilling gun
Drilling guns were originally developed to drill gun barrels and are commonly used for drilling diameter smaller diameter holes. The depth-to-diameter ratio can be greater than 300: 1. The main feature of drilling pistols is that the bits are self-centered; this is what allows for such deep holes. The bits use a rotary motion similar to a rotary drill; However, the bits are designed with bearing pads that glide along the surface of the hole keeping the drill in the middle. Drilling pistols are usually performed at high speed and low feed rates.
Trepanning
Trepanning is generally used to make larger diameter holes (up to 915 mm (36.0 inches)) where standard drill is not feasible or economical. Trepanning eliminates the desired diameter by cutting compact discs similar to how the compass draft works. Trepanning is performed on flat products such as sheet metal, granite (curly stone), plates, or structural members such as I-beams. Trepanning can also be useful for creating a groove to insert a seal, such as an O-ring.
Microdrilling
Microdrilling refers to drilling holes less than 0.5 mm (0.020 in). Drilling a hole in this small diameter presents a larger problem because the drill bore drill is unusable and high spindle speed is required. High spindle speeds that exceed 10,000 RPM also require the use of balanced tool holders.
Vibration drilling
The first study into vibration drilling began in the 1950s (Pr.V.N. Poduraev, Moscow Bauman University). The main principle consists in generating axial vibration or oscillation in addition to the bait movement of the drill so that the chip breaks out and is then easily removed from the cutting zone.
There are two main technologies of vibration drilling: a self-supporting vibration system and a forced vibration system. Most vibration drilling technologies are still in the research phase. In the case of self-managed vibration drilling, the eigen frequency of the device is used to make it vibrate naturally while cutting; vibration is maintained by the mass spring system included in the tool handle. Other works use piezoelectric systems to generate and control vibrations. This system allows high vibration frequencies (up to 2 kHz) for small magnitudes (about several micrometers); they are very suitable for small hole drilling. Finally, vibration can be generated by mechanical systems: the frequency is given by a combination of rotational velocity and the number of oscillations per cycle (some oscillations per cycle), with a magnitude of about 0.1 mm.
This latter technology is entirely industrial (eg SineHolingÃ,® technology from MITIS). Vibration drilling is the preferred solution in situations such as deep hole drilling, multi-material drilling piles (aeronautics) and dry drilling (without lubrication). It generally provides greater reliability and control over drilling operations.
Interpolation Circle
The interpolation circle , also known as orbital drilling , is the process for making a hole using a machine cutter.
Orbital drilling is based on turning the cutting tool around its own axis and simultaneously about the central axis being off of the cut axis of the tool. The cutting tool can then be moved simultaneously in the axial direction to drill or create a hole - and/or combined with sideways movement to the machine to open or dig a cavity.
By adjusting offsets, cutting tools of a certain diameter may be used to drill holes of different diameters as illustrated. This implies that the supply of cutting tools can be substantially reduced.
The term orbital drilling comes from that cutting tool "orbits" around the center of the hole. The forced mechanics, dynamic offsets in orbital drilling have several advantages over conventional drilling that drastically improve hole precision. Lower thrust forces produce drill holes when drilling metal. When drilling the composite material the delamination problem is removed.
Maps Drilling
Materials
Drilling in metal
In normal use, the swarf is carried up and away from the tip of the drill by drill embroidery. The cutting edge produces more chips that continue the movement of the chip out of the hole. This works until the chip pack is too tight, either because the hole is deeper than normal or not enough backwards (removes the drill bit or entirely from the hole during drilling). Cutting fluid is sometimes used to alleviate this problem and extend device life by cooling and lubricating chip ends and flows. Cooling can be introduced through a hole through a borehole, which is common when using a rifle drill. When cutting aluminum in particular, cutting the liquid helps ensure smooth and accurate holes while preventing the metal from grabbing the drill in the hole drilling process. When cutting brass, and other soft metals that can take the drill bit and cause "chatter", face around. 1-2 millimeters can be milled on the cutting edge to create a blunt angle of 91 to 93 degrees. This prevents the "chatter" in which the drill is flowing rather than cutting the metal. However, with a bit cutting edge shape, the drill pushes the metal away, rather than reach for the metal. This creates a high friction and a very hot swarf.
For heavy feed and drill holes are relatively deep drill used in the drill bit, with lubricant pumped to the drill head through a small hole in the bit and flows along the fluting. A conventional drill pressing arrangement can be used in drilling an oil hole, but this is more often seen in automatic drilling machines that are rotary objects rather than drill bits.
In a numerical computer control tool (CNC) a process tool called peck drilling , or cutting drilling cut , is used to keep the swarf from constructing adversely when deep hole drilling (approximately when the hole depth is three times greater than the drill diameter). Peck drilling involves plunging the drill part of the path through the workpiece, no more than five times the drill diameter, and then pulling it to the surface. This is repeated until the hole is finished. A modified form of this process, called high speed peck drilling or chip breaker , only retracts the bit drill. This process is faster, but only used in holes long enough, otherwise it will overheat on the drill bit. It is also used when drilling fibrous material to break the chip.
When is it impossible to bring material to? N? machine, Magnetic Base Drilling Machine can be used. Base allows drilling in a horizontal position and even on the ceiling. Usually for these machines it is better to use a cutters as they can drill faster with less speed. The size of the cutter varies from 12mm to 200mm DIA and from 30mm to 200mm DOC (cut depth). These machines are widely used in construction, fabrication, marine, and oil & amp; gas industry. In the oil and gas industry, magnetic pneumatic drilling machines are used to avoid sparks, as well as special fixed tube magnet drill machines in different sizes, even inside.
Drilling in wood
Wood becomes softer than most metals, drilling in wood is much easier and faster than metal drilling. Cutting fluid is not used or needed. The main problem in timber drilling is ensuring clear inlet and exit holes and preventing burning. Avoiding burning is a question of using sharp bits and proper cutting speed. Drill can tear wood chips around the top and bottom of the hole and this is undesirable in fine woodworking applications.
Drill bit bits used in metal work also work well in wood, but they tend to cut wood at the entrance and out of the hole. In some cases, such as in rough holes for carpentry, hole quality is no problem, and a number of bits for fast cuts in wood exist, including bit spades and self-feeding auger bits. Many types of special drill boring holes in wood have been developed, including brad-point bits, Forstner bits and hole saws. Chipping on the exit can be minimized by using a piece of wood as a backing behind the workpiece, and the same technique is sometimes used to keep the hole in neat.
Holes are easier to start using wood because the drill can be positioned accurately by pushing it into the wood and creating dimples. Thus, few will have little tendency to wander.
More
Some materials such as plastic as well as non-metals and some metals have a tendency to heat enough to expand making the holes smaller than desired.
Related process
Here are some related processes that often accompany drilling:
- CounterboringÃ,
- This process creates a hole in which the larger diameter follows a smaller diameter partially into the hole.
- CountersinkingÃ,
- This process is similar to counterboring but the step in the hole is conical.
- Dull
- Boring actually enlarges existing holes using a single point cutter.
- Friction loading
- drill holes using plastic deformation of the subject (under heat and pressure) rather than cutting it.
See also
- Laser drilling
- Drilling rig
References
External links
- Top Pile Company
- Feeds for high speed training
Source of the article : Wikipedia
0 Comments