Magnetic Drilling Machine
A Magnetic Drilling Machine is a machine tool used for drilling holes in variety of metals. A magnetic drilling machine is a portable drilling machine with a electro-magnetic base or a permanent magnet base. The magnetic drilling machine drills holes with the help of cutting tools like annular cutters (broach cutters) or with twist drill bits. There are various types of magnetic drilling machines depending on their operations and specialisations like magnetic drilling cum tapping machines, cordless magnetic drilling machines, pneumatic magnetic drilling machines, compact horizontal magnetic drilling machines, automatic feed magnetic drilling machines, cross table base magnetic drilling machines etc.[1]
A Magnetic Drilling Machine is also popularly known as a magnetic core drilling machine, magnetic base drilling machine, mag base drilling machine, mag base, magnetic broach cutter machine, magnetic drill or mag drill.
A portable magnetic drilling machine is the best solution for drilling large and heavy workpieces which are difficult to move or bring to the stationary conventional drilling machine for making holes, where as the magnetic drilling machines are so portable and lightweight that the machines can be taken to the workpiece to be drilled. The magnetic drilling machines have popularly changed the method of bringing workpiece to the drilling machine by bringing the machine to the workpiece.
A portable magnetic drilling machine is available in various sizes, shapes, designs, electronics and equipment depending upon the purpose of the machine. It combines the versatility of a drill press with a strong electromagnetic base enabling it to adhere to a carbon steel (ferrous metal) surface. It can be positioned to drill horizontally, vertically or even upside down.[2]
Applications
A magnetic drilling machines can be used at steel fabrication, building and construction, pre-engineered buildings (PEB), bridge construction and maintenance, shipbuilding, railway construction, automobile industry, pipeline, offshore, oil industry, welding shops, power utilities, heavy engineering companies, heavy machine manufacturing, boiler manufacturer, etc.[3]
Parts
A magnetic drilling machine is mainly made from three parts namely magnetic base, metal frame and a DC motor.
Magnetic Base
Generally, an electromagnetic base is equipped with magnetic drilling machines, but recent trends also show machines with permanent magnets. The electromagnet can comprise two, three or four electric coils depending on the power of magnet to be achieved. The higher the drilling diameter & drilling depth capacity of the magnetic drilling machine the more powerful is the magnet required to withstand the adhesion.
Metal Frame
The metal frames are made from cast aluminium or other material depending on the manufacturer. The metal frames have handle to lift the machine and feed-handles to give feed to the motor of the machine. Generally, the magnet switch, power switch, motor rotation switch, magnet indicators, etc are fitted on the metal frame. Recent trend also show that these switches are places on the motor instead of the metal frame depending on the manufacturer. The base of a magnetic drill is equipped with a powerful electromagnet to easily clamp the machine on the work piece to be drilled. When energized this magnet gets strongly fixed on the metal work piece locking the machine base to the metal profile which helps the operator to give a steady feed against the work piece. The electromagnet plays a very important role in a portable magnetic drill, as it helps the machine to be steady, does not let the machine dismount during drilling, can work with the machine overhead, horizontal or vertical. Generally, a magnetic core drilling machines is used on a ferrous material directly, but it can also be used on no ferrous material like stainless steel with the help of clamping devices. The body of the magnetic drill holds together the motor and the magnet base.
Motor
Motor is the main part and heart of a magnetic drilling machine. It plays a very important role on performance and life of the magnetic drilling machines. A magnetic drilling machines capacity can be determined from Wattage of the motor. Generally, all magnetic drilling machines have brush DC motor. For example, 900 Watt power is required for a magnetic drilling machine to drill 35 mm diameter and 55 mm cutting depth. An arbor or chuck on a magnetic drill is attached to the motor. It is a type of clamp used to attach the core drills. There are mainly two types of chuck available for the magnetic drill, industrial arbor (manual tightening) and quick change drill chucks. The quick change drill chucks are easy and fast option to attach the core drills. They do not need to tighten the screws/jaws manually. The arbor or chucks have different types of spindle holder (machine taper) like Morse taper MT 2, MT 3, and MT 4. The chuck allows different types of core drill shafts (shanks) to fit in it. The motor of a magnetic drilling machine can be of two types depending on the lubrication system of gears inside the motor. The two types are grease gearbox motor and oil bath gearbox motor.
Grease Gearbox Motor
As the name suggests the grease gearbox motor have grease inside the gearbox which lubricates the gears. This technology is an economical technology which makes the cost of the machine low. The disadvantage of grease gearbox motor is that when the machine is in an idle condition, grease is in a solid stage, when the machine starts to run the motor gets warm up and grease changes its form from solid to liquid hence decreasing its level inside the gearbox. Thus, due to the decrease in level of liquid grease the upper positioned gears inside the gearbox does not get enough lubrication and may result in breakage of gears. This factor decreases the life of the motor.
Oil Bath Gearbox Motor
An oil bath gearbox is considered to be the heavy duty gearbox for magnetic drilling machines. As the name suggest this gearbox are filled with lubrication oil. The advantage of oil is that, oil is always in its liquid state even in cold condition or when the motor is very warm. The liquid state of oil gives lubrication to all the gears on upper level as well as lower level, hence the life of gears is drastically extended and the magnetic drilling machine gets longer service life. The oil bath gearbox needs specialised sealing, this sealing technology makes the oil bath gear box more expensive than grease gearbox.
Types
There are various types of magnetic drilling machines available in the market depending on its purpose of use and specialty.
Lightweight Magnetic Drilling Machine
The lightweight type of magnetic drilling machines are very useful for drilling on higher location like tower, building, structures where the weight of the machine to be carried manually is important. these type of machines have power in the range of 800-100 watts and can drill up to 32 to 35 mm diameters with broach cutters. Lightweight magnetic drilling machines fall in the range of 9 Kg. to 12 Kg. category. These type of machines are meant only for drilling and not for tapping operations.
Magnetic Drilling cum Tapping Machine
A magnetic core drilling machine fitted with a reversible motor can also be used for tapping, countersink and reaming operations. These type of magnetic drilling cum tapping machines have become very popular as a substitute for the hand tapping method. These type of machine uses machine taps to make the threads. The basic requirement for a mangnetic drilling cum tapping machine is to have a reversible motor, variable speed contro and variable torque control. The reversible motor helps the taps to return back after the thread is made without damaging the thread and the tap. The reversible motor also helps in making left-hand taps. Such type of machines are available in capacity for making taps from M6 up to M42 depending on the model of the machine. Compared to hand tapping operations which takes more time and uses primary, secondary and tertiary taps to make a single thread, the magnetic drilling cum tapping machines are faster and use only one tap (no need for primary, secondary and tertiary taps).
Magnetic Drilling Machines with Swivel Base
The modern magnetic drilling machines now also come with an option of Swivel Base. The swivel base can rotate in left and right in certain degrees like 30°- 45°. This helps the operator to make multiple holes beside each other without demagnatizing the machine every time and moving it. With swivel base the magnet of the machine is kept activate and only the body of the machine can be moved in angle to position for other holes to be made nearby. The swivel base is very important for drilling on horizontal or overhead position because in this situations the machines has to be lifted and along with the heavy weight of the machine it has to be placed and positioned correctly at the hole marking. If the machine is not positioned exactly the operator needs to again deactivate the magnet and reposition the machine carrying heavy weight. This is avoided by the swivel base, while the operator can approximately position the machine overhead or horizontal near the hole marking and with the help of swivel base the operator can exactly position the body of the machine on the hole marking without demagnetising the machine. How the swivel base works: place the machine roughly in position, activate the magnet, release the adjustment feature and adjust it effortlessly. The swivel base enables the drill to be placed in exactly the right position without needing to hold the whole weight of the machine at the same time. This relief is an additional factor in work safety even when the machine is secured with a chain.
Compact Horizontal Magnetic Drilling Machine
Horizontal magnetic core drilling machine with angular gear, are ideally suited for most confined drilling situations. These machines are specially designed to make holes between I-beam or H-beam, confined locations like bridges, etc. The height of compact magnetic drilling machines ranges between 180 mm to 210 mm. The motor fitted with this machines are powerful and some modern compact magnetic drilling machines are now also equipped with LED light to drill holes in confined situations in darkness. A cutting depth of 30–35 mm can be achieved with compact magnetic drilling machines.
Automatic Magnetic Drilling Machine
The automatic drilling machines in recent days are becoming more and more popular due their variety of advantages. The automatic drilling machines takes the feed automatically and once the hole is made the reverse feed is also automatic. The advantages of automatic drilling machines are that the performance of the machine is independent of operator skills, the life of tool increased drastically due to steady feed, one operator can operate multiple simultaneously, steady flow of lubrication is achieved, the quality of the hole made is also improved and most important the time is saved. An automatic magnetic drilling machine is available in various capacities depending on the manufacturer like 35 mm, 50 mm, 100mm and 130 mm diameter. The modern automatic magnetic drilling machines are also equipped with overheat protection, overload protection, magnet adhesion indicator, etc. The automatic magnetic drilling machines are also idle for drilling with conventional drill bits.
Cordless Magnetic Drilling Machine
The next generation of magnetic drilling machines are the cordless types. A cordless magnetic drilling machine is equipped with li-Ion battery which is charged internally or externally with an electric power supply. These machines are suitable for drilling at remote locations, on heights or location with electricity supply shortage. Generally with one charge a magnetic drilling machine can make up to 40 holes depending on the model and manufacturer. Many manufacturers have started research and development to make this technology better and more economical. Currently, there are only handful of manufacturers which have cordless magnetic drilling machines in their product range.
Drilling Non-Ferrous Materials
The magnetic drilling machine due to the properties of magnet can be easily used on any ferrous material, but on non-ferous material the magnet can not work. To drill non-ferrous materials like aluminium or stainless steel, the magnetic drilling machine has to be used with a clamping device such as Vacuum Plates.[4]
Drilling Tubes and Pipes
The magnetic drilling machines can also be used for drilling large tubes and pipes with the help of clamping devices such as Tube Clamp.
Drilling Small Parts
Due to the size of the magnet of the magnetic drilling machines, one can not put the machine over small parts and drill. To drill small parts a moblie stand with wise is needed.
Drilling Small Plates
Due to the size of the magnet of the magnetic drilling machines, one can not put the machine over small plates whose width or length is too less compared to the magnet size. To drill small plates a table top magnet clamp is required.
Formula For Calculating RPM
The magnetic drilling machines are provided with speed gears and some machines are also equipped with variable speed control. As per the diameter of the annular cutter and the type of annular cutter the speed of the magnetic drilling machine has to be set.[5]
The formula for calculating the speed is:
n = (v X 1000) / (d X Pi) = min-1
d = diameter of the annular cutter in mm.
v = cutting speed of the annular cutters. See below chart for cutting speeds.
References
- ↑ "What is a Magnetic Drilling Machine? » Broach Cutters India". Broach Cutters India. 2017-03-22. Retrieved 2017-03-21.
- ↑ "What is a Magnetic Drilling Machine? » Broach Cutters India". Broach Cutters India. 2017-03-22. Retrieved 2017-03-21.
- ↑ "The professional way to use Broach Cutters and Mag Drills | | BDS Machines Pvt. Ltd.". BDS Machnes Pvt. Ltd. 2017-03-08. Retrieved 2017-05-08.
- ↑ "How to clamp the magnet on ferrous and non-ferrous material or non-magnetic material?". Magnetic Drilling Machines .com. 2016-07-14. Retrieved 2017-03-21.
- ↑ "uae-magneticdrillingmachine.com". uae magnetic drilling machine.