Embedded Files
- Hand Tools
Dividers
Dividers
Workshop Spring Dividers (or compass) are used for marking out work. Sharp points can be used to scribe the workpiece, creating arcs and circles. They can also be used to measure the distance between two points. They provide a high degree of accuracy and repeatability.
Oddleg calipers are used mainly to scribe lines parallel to the edge of metal (or plastics) - they are used for much the same reason that a woodworker might use a Marking Gauge. Oddlegs can also be used to find the centre of a disc by first estimating its radius then scribing a number of arcs from different points around the circumference. The various arcs will enclose a small area in which the centre must lie and so can be judged.
Note: To make scribed lines stand out more, bright steel can be coated with Marking Blue (or a felt tipped pen) whilst black steel or rusty metal can first be rubbed with chalk.
Snips
Snips
Aviation snips are designed to cut sheet metal in a straight line(yellow) or curves to the right with the waste material on the right (green) or curves to the left with the waste material on the left (red). You can use the snips with either hand, but if you're right-handed you'll find it easier to use green snips for many types of cuts.
Scriber
Scriber
A scriber is a hand tool used in metal work to mark lines on workpieces, prior to machining. Some scribers have a point at both ends. It is used by dragging the point over the surface of the workpiece to leave a shallow scratch on its surface.
When you scribe a line, draw it once. Going over the line several times causes wide, inaccurate lines and dulls the scriber. The scriber should be tilted so that the point contacts the guiding edge of the measuring tool to scribe a neat, accurate line. Drag or pull the scriber instead of pushing it. Pushing a scriber can cause it to bounce and produce irregular lines.
Hammers and Mallets
Hammers and Mallets
Ball-peen - A ball-peen or ball pein hammer, also known as a machinist's hammer, is a type of peening hammer used in metalworking. It has two heads, one flat and the other, called the peen, rounded. It is distinguished from a cross-peen hammer, diagonal-peen hammer, point-peen hammer, or chisel-peen hammer by having a hemispherical peen. The flat side is used for striking punches and chisels and the rounded head, is useful for tasks such as rounding off edges of metal pins.
Tinsman Mallet - A mallet is a kind of hammer, often made of wood and usually has a relatively large head. Mallets are used in various industries, by carpenters, furniture makers, sheet metal workers and upholstery work. It is a tool of preference for wood workers using chisels with plastic, metal, or wooden handles, as they give a softened strike with a positive drive. The Tinsman mallet is used to shape or bend sheet metal.
Spring Dividers
Aviation Snips
Scriber
Ball-pein Hammer
Measuring Equipment
Measuring Equipment
Combination square
The square head and blade (rule) of the combination set are called the combination square. It can be used in semi-precision layout operations to scribe straight lines and to lay out lines that are perpendicular, or square, to the edge of the workpiece. Place the square head against the edge of a piece of material and use the blade (rule) to guide a scriber to scribe the line.
Combination set
The combination set consists of a blade, square head, center head and protractor head. The different heads are mounted to the blade by tightening a clamping screw. The centre of round material can be found with the use of the centre head and blade as shown in the adjacent image.
Angular measurements can be made using a normal protractor or when the protractor head is mounted to the blade of a combination set.
Combination set
Finding centre using centre head.
Vernier Protractor
When angles need to be measured more accurately than within 1 degree, the vernier bevel protractor can be used. It has 5 minute (1/12th degree) graduations. With an acute angle attachment, the protractor can more easily measure angles less than 90 degrees.
Vernier Calipers
A vernier caliper is similar to a semi-precision slide caliper, but its vernier scale allows it to be used for measurements as small as 0.02mm. A vernier caliper has a solid jaw and a moveable jaw that are brought in contact with part surfaces to measure external dimensions. Internal dimensions are measured by placing the "nibs" between two surfaces. Some vernier calipers also have a depth rod for depth measurement.
Advancement in technology has seen the development of digital calipers, which makes reading vernier scales easier and more efficient.
Vernier calipers
Micrometer
The micrometer is a precision measuring tool that uses a very accurate screw thread to perform measurement. It has one stationary point of contact and another that moves as the screw is rotated. A graduated scale on the tool then shows the distance between the two points of contact equal to the measurement. Micrometers come in many different sizes and styles for different applications, such as Inside Micrometers, Outside Micrometers, Depth Micrometers, Multiple-Anvil Micrometers, Screw Thread Micrometers and Larger Scale Micrometers.
Outside micrometer
Files
Files
FIles are used in benchwork for tasks such as shaping, smoothing, fitting, and deburring. It is essential to learn how to properly use files when filing is a more practical method than a machine tool. Files are available in a multitude of shapes, sizes, and styles for different applications.
Files can be classified according to:
Length - measured from the heel to the tip of the file
Cross section - Flat, Square, Round, Half Round, Three Square, Mill, Pillar and Knife
Cut or tooth type -
Single cut - have a single set of teeth
Double cut - have a second set of teeth perpendicular to the first set. Used for faster removal of material.
Rasp - Large teeth, uncommon in machining as it is used to quickly remove soft material like timber.
Coarseness - From coarsest to smoothest, Rough, Bastard, Second-cut, Smooth and Dead Smooth.
Cuts and tooth types
File Selection
File Selection
When selecting files, longer, coarser, double-cut files are generally chosen to remove material quickly, while shorter, finer, single-cut files are generally chosen to create smoother finished surfaces. With practice and experience, you will begin to develop a sense of what type of file to use for different situations, since every job is unique.
As you use files, their teeth will eventually become clogged with the materials you are removing. This is called loading. Sometimes, particularly on softer metals such as aluminium, particles of the material being filed called pins can embed in the teeth. This is called pinning. Pinning and loading will occur more quickly if you use too much pressure. Clear your file frequently to keep pins from scratching the workpiece. If you notice scratches in the material, it's a sign that you need to clean your file. File cards are brushes used to clean files. A file card can have short soft or wire bristles. Many of them also have a small pick that can used for removing pins. To remove the pins, use the pick and slide it between the teeth to push out the pins. Move the brush parallel with the angle of the teeth.
Coarseness
2. MIG Welder
2. MIG Welder
What is MIG Welding?
What is MIG Welding?
Metal Inert Gas (MIG) welding is an arc welding process in which a solid wire electrode is continuously fed through a welding gun into a weld pool. An arc is formed between the wire electrode and base metal, melting the base material while consumable filler wire is deposited, creating the weld.
At the same time, a shielding gas is fed through the welding torch to protect the weld from outside contaminants.
MIG welding is also known as Gas Metal Arc Welding (GMAW).
How Does MIG Welding Work?
How Does MIG Welding Work?
The MIG welding process is relatively straightforward, and most of it is automated too.
MIG welding is always done on direct current (DC), which means that the current only runs in one direction. Like a battery, it requires a completed electrical circuit to work. All the components of the welder work together to form this circuit.
First, a wire spool is loaded into the machine. This wire is fed through the driver rollers, into the torch liner and out of the contact tip and nozzle. The wire will start feeding continuously when the torch trigger/button is pressed and stop when it’s released.
Pressing the torch trigger will also start the gas (if it’s needed), which is fed through the nozzle to shield the weld.
The wire plays two parts: heat source and the filler material. When the wire passes through the copper contact tip, it becomes electrically charged with the welding current. The wire comes out of the torch and touches the base metal, creating an arc between the two.
That’s the first half of the electric circuit formed.
The arc melts both metals, depositing filler metal into the molten base metal to form a weld. There are several ways filler metal can be transferred from the wire into the base. Your normal MIG welding transfers metal via the short circuit mode.
Click the following link for information on other modes of metal transfer.
The final piece of the puzzle is the earth clamp. Without it, your machine won’t arc. You can still pull the trigger and feed the wire through your torch, but all you’ll end up with is wasted wire.
The earth clamp completes the electric circuit that runs from the machine, through the torch, into the base metal, and then back up the earth clamp to the machine.
On top of that, getting a proper grounding is important because a bad earth can cause several issues, including burnback and a wandering arc.
MIG welding is considered a semi-automatic process. The wire feeding is automatic, but the torch movement is still manual, making it semi-auto.
Settings (Voltage & Wire Feed Speed)
Settings (Voltage & Wire Feed Speed)
There are only two settings on MIG dedicated machines: voltage and wire feed speed.
The voltage determines how much heat is in the weld. Turning it up or down will adjust how much welding current is added to the weld.
The wire feed speed determines how much wire per minute is added to the weld. The more wire that’s added, the cooler the weld will be, and vice versa.
Your voltage and wire feed speed generally work in harmony together. If you turn your wire feeding to the max but leave your volts too low, the wire won’t burn. You need enough heat to melt the wire, but not so much heat that it gets sprayed everywhere except in the weld.
What you want to set them to depends on a few things. The metal thickness, the metal type, filler wire thickness, weld position and joint type will all impact the settings.
If you’re not sure where to start, almost every UNIMIG MIG welder comes with a Setup Guide on the inside of the machine’s door. It provides recommended settings for different metal types, metal thicknesses and wire sizes as a starting point. It also includes the gas flow and polarity recommended for each application.
Polarity
Polarity
Getting the polarity right is pretty important, as it impacts the quality of the weld. The wrong polarity will leave you with excessive spatter, an uncontrollable arc and poor penetration.
Gas MIG welding runs on an electrode-positive polarity. That means the current is positively charged and runs from the negative to the positive. It’s most commonly referred to as reverse polarity or DCEP (Direct Current Electrode Positive).
To set up a UNIMIG welder for DCEP, plug the polarity cable in the positive (+) panel mount and the earth clamp into the negative (-) panel mount.
Gas MIG electrode positive
Keep in mind, only gas MIG uses DCEP. The polarity is flipped to DCEN (Direct Current Electrode Negative) if you’re looking to weld with flux-cored (gasless) MIG wire.
That means you’ll plug your torch/polarity cable into the negative (-) panel mount and your earth clamp into the positive (+) panel mount.
Gasless MIG electrode negative
Unimig 350 Razor MIG/TIG/MMA
Metals
Metals
MIG welding is one of the more versatile when it comes to the different materials that it can be used on. These metals include:
Mild steel
Stainless steel
Aluminium
Copper
Bronze
Wire Electrode Selection
Wire Electrode Selection
There are two things to consider when picking your filler wire. Making sure the base and filler metals match and getting the right size.
You want your wire metal and its grade to be as close a match to your parent metal as possible. If you’re welding with mild steel, you’ll need mild steel wire. If you were welding aluminium, you could choose 5356 or 4043 or another grade wire, depending on your parent metal
Filler wires of the same metal as your base metal will work even if the grades aren’t an exact match. Don’t worry if you’re not sure what grade your metal is; just match the metals.
The other thing to consider is how thick your wire is. If you’re working with sheet metal, you’re not going to want filler wire that’s 1mm thick. Your wire should be thin enough that it’ll melt but thick enough that there’s enough metal deposited to form a proper join.
A good all-around wire size is 0.8mm. You can drop down to 0.6mm for very thin metal or go up to 0.9mm for thicker applications.
Shielding Gas
Shielding Gas
Shielding gas is used to protect the weld from outside contaminants. The gas you can use will vary depending on the type of metal you’re welding. Different gases also have different effects on the weld.
The most common (and generally best) shielding gas you can use for mild and stainless steel is a 75% argon/25% CO2 mix. It helps stabilise the arc and deepen penetration while shielding the weld. For aluminium welding, pure argon gas is needed for shielding.
Advantages of MIG
Advantages of MIG
There are a lot of things that make MIG a great choice, not just the fact that it’s easy to learn (though that is one of them!).
It’s versatile. MIG welding can be used on a wide variety of metal types and thicknesses, covering most welding applications.
It’s more efficient, with higher productivity compared to other methods. Because MIG wire comes in large spools (1kg, 2kg, 5kg & 15kg), there’s less downtime than if you were swapping rods or chipping off slag. It also has a higher deposition rate, and there’s no electrode stub loss.
It’s fast. On top of not needing to constantly replace your filler, MIG welding is the fastest type of welding.
It’s easy to learn. Being a semi-automatic, point-and-weld process with two settings makes it the best type of welding to learn as a beginner.
It welds in every position. MIG welding works regardless of whether you’re in a flat, horizontal, vertical, or overhead position.
It’s relatively clean. Okay, so it’s not as clean as TIG welding, but MIG still produces minimal spatter, and there’s no slag involved at all, saving you time and effort.
It produces aesthetic, high-quality welds. The ease of use, automatic wire feeding, and clear visibility of the weld pool means producing a good weld is easy.
Disadvantages of MIG
Disadvantages of MIG
While it might be the most popular type of welding, that doesn’t mean there aren’t a few downsides to MIG.
The initial cost. When first purchasing a MIG welder, the cost of the machine, gas, filler wire and other consumables can add up. It’s not as cheap to get going with MIG as it is with stick. The good news is that your MIG machine should last you years.
It’s not suited for the outdoors. Any kind of wind or breeze will blow your shielding gas away, leaving your weld exposed to contaminants. However, there are some solutions, like setting up welding curtains or other barriers. You could also swap to gasless MIG.
It’s not very portable. The fact that you need a bottle of gas means that moving the welder around frequently isn’t the easiest task.
It can’t weld through dirt and rust. Your base metal will need to be clean before it can be welded on. This is true of most welding, though there are more forgiving weld methods than MIG in this regard.
In summary, MIG welding is fast, efficient, simple to set up, easy to learn and used for almost everything. If you’re just getting into the world of welding, it’s the perfect place to start.
3. Oxy-Acetylene
3. Oxy-Acetylene
Oxy-fuel equipment is quite versatile, not only because it is preferred for some sorts of iron or steel welding but also because it lends itself to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), rust, or scale removal, the loosening of corroded nuts and bolts, and is a ubiquitous means of cutting ferrous metals.
The torch is the tool that the welder holds and manipulates to make the weld. It has a connection and valve for the fuel gas and a connection and valve for the oxygen, a handle for the welder to grasp, and a mixing chamber (set at an angle) where the fuel gas and oxygen mix, with a tip where the flame forms. The common types of torches are:
Welding
Cutting
Rose Bud
Injector
Air-acetylene produces a flame temperature of around 4000° F (2200° C). This is hot enough to solder aluminum work glass, repair radiators and braze plumbing fixtures. It is not hot enough to weld steel. When acetylene is burned in pure oxygen, the flame temperature may be as high as 5730° F (3166° C).
Types of flames
Types of flames
Neutral Flame: A neutral flame results from equal volumes of oxygen and acetylene being used. The inner core of the flame is long and clearly defined within the outer envelope. The neutral flame is used for the majority of welding requirements with steel, cast iron and copper.
Oxidising flame: An oxidising flame is obtained by first setting a neutral flame, then reducing the acetylene to shorten the inner cone. The oxidising is used when welding brass alloys as the chemical effect of the free oxygen tends to prevent loss of zinc from the parent metal.
Carburising Flame: A carburising flame is obtained by using an excess of acetylene. Through welding goggles the parts of the flame are clearly visible; an intense but feathery-edged inner core surrounded by a luminous secondary cone and a bluish outer envelope forming a third zone. A carburisng flame is generally used for welding aluminium, bronze and nickel alloys.
4. Cutting Equipment
4. Cutting Equipment
Hacksaws
Hacksaws
The hacksaw is used to cut steel and other metals. It can also be used to cut plastics, although it is not normally used to cut woods. It is sometimes called an adjustable hacksaw because the length of the frame can be altered to hold blades of different sizes. Blades are supplied in two lengths, 250mm and 300mm. If the adjusting screw is unscrewed, the frame can be pushed into the handle so that the smaller blades fit the hacksaw.
Blades are also described by the number of teeth per inch (TPI). Blades have 14, 18, 24, 32 teeth per 25mm (inch). A blade with 14 TPI is coarse whilst a blade with 32 TPI is very fine.
Technique
Technique
Selecting the correct number of teeth per inch (25mm) is also important. The general rule is that at least three teeth should extend across the surface of the material to be cut. One hand holds the hacksaw handle with the index finger pointing in the direction of cutting (pistol grip). The other hand holds the frame, near the wing nut. Cutting/sawing should be carried out close to the jaws of the vice. This ensures that the metal does not flex or bend under the force of the hacksaw and the sawing motion. When the metal has been cut, it will need filing. This removes sharp ‘burrs’ so that the metal can be handled safely, without the possibility of cuts to the hands.
Selecting the correct blade
Selecting the correct blade
Blades eventually wear or break and need replacing. The blade can be replaced by loosening the wing nut adjuster until it comes off the two ‘studs’ that normally hold it in tension in the frame. A blade should always be positioned with its teeth pointing away from the handle. Two types of hacksaw blade are generally available. High Carbon Steel blades are used for general cutting/sawing. They do not last as long a High Speed Steel blades. These are much more expensive but keep their cutting edge for longer and are suitable for cutting hard materials such as stainless steel and alloys. Selecting the correct blade for the material to be cut is important when setting up a hacksaw. High Speed Steel (HSS) blades are used for tough, resistant materials whilst High Carbon Steel blades are for general cutting.
Cold Saw
Cold Saw
A cold saw is a circular saw designed to cut metal which uses a toothed blade to transfer the heat generated by cutting to the chips created by the saw blade, allowing both the blade and material being cut to remain cool. This is in contrast to an abrasive saw, which abrades the metal and generates a great deal of heat absorbed by the material being cut and saw blade.
As metals expand when heated, abrasive cutting causes both the material being cut and blade to expand, resulting in increased effort to produce a cut and potential binding. This produces more heat through friction, resulting in increased blade wear and greater energy consumption.
Cold saws use either a solid high-speed steel (HSS) or tungsten carbide-tipped, resharpenable circular saw blade. They are equipped with an electric motor and often a gear reduction unit to reduce the saw blade's rotational speed while maintaining constant torque. This allows the HSS saw blade to feed at a constant rate with a very high chip load per tooth.
Cold saws are capable of machining most ferrous and non-ferrous alloys. Additional advantages include minimal burr production, fewer sparks, less discoloration and no dust. Saws designed to employ a flood coolant system to keep saw blade teeth cooled and lubricated may reduce sparks and discoloration completely. Saw blade type and number of teeth, cutting speed, and feed rate all must be appropriate to the type and size of material being cut, which must be mechanically clamped to prevent movement during the cutting process.
Blade Selection
When selecting the best cold saw blade for your application, this is the number one, and most important question you should be asking yourself. How many teeth do I need on my cold saw blade?
Selecting the optimal number of teeth for your application will deliver you the best performance and blade life. Typically you want 2 to 4 teeth in your material at all times. The smaller/thinner the material, the more teeth required on the blade to ensure it does not grab the material while operating the machine.
The chart below provides detailed information on the blade diameter required for common-sized material used in the Industrial Technology workshop.
Plasma Cutter
Plasma Cutter
Machine Setup
Air/Gas
Torch & Consumables
Settings
1. Air/Gas
Unlike welding machines, every Australian market plasma cutter you can buy is made to work on compressed air only. The good news is that an air compressor attaches to the back of a plasma cutter in the same way a gas tank connects to the back of a welder.
The need for an air compressor means they’re not very portable because you need to be connected to the compressor and a power supply. When purchasing a compressor, make sure to get one that can deliver 70–120psi and has an airflow/intake volume rating that is greater than your plasma cutters. You don’t want to run out of air before you’ve finished your cut.
If you’re looking for more portability, some machines come with built-in air compressors. These machines will still need a power supply, however.
An air dryer or filter is essential for keeping contaminants like moisture and dust particles out of the machine’s air lines. Moisture in the pipes will come out in your torch and cause your consumables to burn up faster, resulting in bad cuts, which is something you’d like to avoid.
Depending on which model machine you have, your air dryer/filter can be found inside the machine or at the back of the machine.
3 types of filter
Basic: most plasma cutters will come with a basic air filter. These will work fine, especially if you’re only doing small cuts on hobby projects, but additional, higher quality air filters are still recommended. If you choose to upgrade your air filter, the original basic filter will remain attached to your machine, and the new filter is attached as an extra unit. Basic air filters are self-draining, with a small hose that sticks out the bottom for the captured moisture to drip out.
Roll: these filters look similar to a toilet roll, which is where they get the nickname ‘toilet roll filters,’ and consist of a cylindrical cartridge. The roll works well, but it’s not self-draining, which means they need to be changed every so often depending on the frequency of use.
In-line: these sound cool, but in reality, they’re not that good. Made from specially treated plastic, it works by closing up when moisture touches it to block the water from getting through. The problem? Airflow is one of the most important things when running a successful plasma cut, and these filters block the moisture as well as the airflow when they close.
Both roll and in-line filters are mostly needed in high-humidity environments
2. Torch & Consumables
Plasma cutting is done in DCEN (Direct Current Electrode Negative). Getting the polarity correct on your plasma cutter is a lot easier than any form of welding because the plasma torches have a different shaped plug.
There’s no guesswork involved with this one; you literally can’t connect your earth clamp or torch into the wrong hole.
Quick Tip: don’t clamp your earth to the bit of metal that will be cut off, as you could then become the path of least resistance, which is not a good time. Make sure to attach your earth clamp to either a (clean) metal workbench or the part of the metal that will not fall away once it’s cut.
Because plasma cutting machines come with a specific plug for the torch and only the Positive (+) polarity panel mount, you can’t use them for anything else, unlike welding machines, which are generally mix and match (to a degree).
Electrode
Swirl ring (gas distributor)
Cutting tip
Shield cap body (retaining cap)
Shield cap
Consumables
The attachments on your torch will make a significant difference to the type of cutting you can do with your machine.
Types of Shields
Contact cutting: contact cutting is what it sounds like; you place the tip of the gun against the metal you want to cut, and off you go. Some torches come with a contact cutting shield cap so that the cutting tip doesn’t touch the metal (as this can wear your tip out), but some machines don’t, in which case the tip itself will be pushed along the metal.
Gouging: gouging is used when you want to remove metal from a piece without actually cutting through it. It’s generally used to remove defective welds so that you can redo them.
Stand off cutting: stand off cutting is similar to contact cutting, except you are forced to leave a space between the torch and metal, as the shields come with little legs or small wheels known as ‘stand off guides’. This process gives your consumables extra life as they remain at a distance from the sparks.
In general, regardless of the type of cutting you want to do and the shield you attach for it, there are several consumables inside the gun which remain the same, though they may look slightly different.
Note: Different guns will allow for more or less varieties of shields to be attached.
3. Settings
Amperage
Unlike welding, the amps you set your machine to will not affect your cut all that much, so long as you adjust your travel speed to compensate. You can set your machine to its max amps and cut every thickness of metal, but if your machine goes up to 80A and you’re cutting 2mm steel, you’re going to have to fly across the cut to avoid warping or completely melting the metal.
You’ll also need to make sure you’ve got consumables in your torch that can handle the amps you’re putting out. If you have a machine set to 80A with consumables only capable of handling 60A max, you’re going to burn through them.
Air Pressure
In general, the air pressure regulator can be found on the back of the machine above the air filter. The regulator will have a hose that runs in on one side and out on the other, with a twistable valve on top. This valve is how you change the air pressure, which you can see on the pressure gauge.
Most machines come pre-set at a pressure level that will work well regardless of the amperage, and the regulator is inside the machine. A good starting pressure regardless of the machine is 75psi.
The amps and air pressure do work together, so if you’re cranking your amps as high as they can go, you’ll want to up your air pressure as well. You don’t want one overpowering the other, as it’ll give you a poor-quality cut
2T vs 4T
2T (two touch) means you will need to hold the button down while you cut. In 4T (four touch) mode you will only need to click the button to ignite the arc, and it will stay ignited until you click it again to turn it off. This setting works the same way that a welder’s 2T/4T setting works, but there’s no foot pedal option.
Air Test
The air test light looks like a gas bottle, and this will check that your air is flowing through the torch at the correct pressure.
Perforated Metal
This setting will have an image of a plasma cutter over a dotted line and will allow you to cut over mesh and other perforated metals. The torch arc will automatically cut out on standard settings if it can’t find metal to complete the electric circuit, so switching to this mode will keep your arc steady for a smooth cut. Otherwise, you’ll have to keep pulling the trigger to start the arc over and over.
5. Drill Press
5. Drill Press
The drill press is one of the most basic machine tools used in the machining field. The drill press performs holemaking operations by pushing a rotating cutting tool into the workpiece. The spindle is the part of the drill press that holds and rotates the cutting tool. Spindle speed is the term used in machining to refer to the RPM of the machine's rotating spindle. Advancement of the cutting tool into a workpiece is called feed.
Common operations performed on the drill press include drilling, reaming, countersinking, counterboring, spotfacing and tapping. Drill presses can provide greater power and control than hand-held electric drills when performing holemaking operations and are available in different styles and sizes depending on the type of work to be performed.
When operating the machine, workpieces should always be secured tightly in a machine vice that is placed on the table of the drill press. Ensure your fingers are clear of the slots in the table as a safety precaution in case the drill bit grabs in the workpiece, which may causes the machine vice to rotate. As a general rule:
Large drill bit = Slow spindle speed
Small drill bit = Fast spindle speed
Calculating RPM
Calculating RPM
Machine RPM for drilling can be calculated in the same way as for turning on the metal lathe, except that the drill diameter is used in the calculation. The formula for approximating spindle speed (RPM) can also be used for drilling RPM.
Note: When using the chart and formula, the cutting speed must be multiplied by 1000 so all dimensions are in millimeters.
Using the spindle speed chart
If the cutting speed and drill size are known, RPM can be read from a spindle speed chart such as the one below. RPM is found by reading down from the nearest cutting speed value and across from the nearest diameter value (drill size).
The RPM value read from the chart could be adjusted proportionally depending on how close the nearest cutting speed and diameter values on the chart are to actual values. However, for most drilling operations rough approximations will usually do.
Spindle Speed Chart
Example 1
A drilling machine with the following spindle speeds is to be used to drill mild steel bar with a 6mm high speed steel drill bit:
Available speeds are 100, 440, 860, 1280, 1620, 2040, 2580 and 2900 RPM.
Using the charts above, select the most suitable of the available spindle speeds.
Cutting speed for mild steel when drilling is 24m/min which is found on the cutting speed chart.
The closest cutting speed on the spindle chat is 25m/min.
Trace that down to the 6mm diameter drill bit row.
The speed on the chart is 1326 RPM.
The closest speed on the available drill press is 1280 RPM.
Using the cutting speed chart
The cutting speed chart can be used for both lathe operations and drilling operations. Note that there are two specific columns for each operation which correspond to different cutting speeds for materials depending on what process is being performed.
When completing calculations, ensure you are selecting the cutting speed for the relevant task e.g. Mild steel has a cutting speed of 30m/min when turning, but has a cutting speed of 24m/min when drilling.
Cutting Speed Chart
Example 2
Calculate the lathe RPM for rough turning a mild steel bar of 42mm diameter with a high-speed steel cutting tool.
The basic formula for calculating revolutions per minute is:
RPM = Cutting Speed/Circumference.
When using a high-speed cutting tool, the cutting speed for rough-turning mild steel is 30 metres per minute. Circumference of the bar is calculated as follows:
Circumference of the bar = ℼ x diameter of the bar
= (22/7) x 42mm
= 132mm
RPM = Cutting Speed/Circumference
= (30m/min x 1000) / 132mm
= 230 approximately
(Note that the cutting speed 30m/min is multiplied by 1000 to convert to mm)
Drill Bits
Drill Bits
There are two common types of material used for cutting tools which are High-speed steel (HSS) and Tungsten carbide. HSS is very popular due to its low cost, and ability to flex under impact without breaking or chipping. HSS can be combined with other alloying ingredients such as cobalt. Some cutting tools may have up to 8% cobalt added to them. These HSS tools are often labeled simply "cobalt". This variety of HSS offers the same advantages as standard HSS, but can operate at up to 10% higher speeds and feeds due to its slightly higher hardness, better toughness, wear resistance, and heat resistance.
Tungsten carbide offers superior tool life due to its extreme hardness, wear resistance, and ability to withstand heat. While carbide is good at many things, it is also very brittle, and easily chipped under impact. While some tooling is made of solid carbide, more economical tooling is available that uses small pieces of carbide as the tool's cutting edges. The carbide pieces can either be mounted to the steel tool body by brazing or by screws. Tooling using replaceble carbide held in place with screws is known as inserted or indexable tooling.
Twist drills
A twist drill can be divided into three main parts:
Drill point - cone-shaped area at the tip of the drill bit. The drill point is made up of sub-parts: the lips are angled cutting edges that shear the metal into chips as the drill rotates. The lips are the only part of the drill that actually cuts. The angle of the lips on a general-purpose twist drill is 118 degrees. The chisel edge is also sometimes called the dead centre and lies between the lips at the centre of the drill point. The rotating chisel edge is the pivot point of the drill and does not actual cutting.
Drill body - extends from the tip to the beginning of the shank and makes up majority of the drill bit. The drill body is made up of the following parts: flutes (pathway for chips to flow out), margin, body clearance, helix angle and the web (connects the flutes and makes up centre part of the bit).
Shank - provides an area for mounting the drill bit into some type of holder.Shanks can be tapered and are more common on larger drill bits. The more taper is a popular standardised style of taper used in drill press spindles.
Parts of a twist drill
Drill sharpening
Drill sharpening
Twist drill points will wear as they are used, and may become damaged, so it is important to know how to resharpen drills by hand to keep them sharp and reduce tool replacement cost. Twist drills can be resharpened many, many times before they need to be replaced. The following basic steps can be performed using a bench grinder:
Hold the drill with the cutting lip, at 59 degrees (approx. 60) to the wheel face, with the tip slightly higher than the shank.
Lightly touch the lip against the wheel and lower the shank end of the drill to move from the lip toward the heel. Apply more pressure when moving toward the heel to create the 8- to 12-degree lip clearance. Repeat the process three times.
Repeat with the other lip and as needed to remove any wear or chips at the cutting edge.
Check the drill point angle and lip length with a drill point gage and grind as needed to create the proper angle and make both lips the same
Check the angle of the dead centre and the lip clearance with a protractor.
Drill sharpening angle using a bench grinder
6. Vertical Milling Machine
6. Vertical Milling Machine
Conventional, or manual, milling machines are primarily used to machine flat and angled surfaces by feeding a workpiece into a rotating cutting tool to remove material. They are also commonly used to position work more accurately for the same type of hole-making operations than can be accomplished with a drill press. By combining these operations, components can be machined to countless described shapes.
The vertical spindle milling machine is widely used in many machining careers in many different industries. Movements of the vertical milling machine are often identified by the Cartesian coordinates system using X-, Y-, and Z-axes.
Parts of the Mill
Parts of the Mill
Knee
The Knee is a heavy casting with a dovetail slot at its rear. This slot is used to attach the knee to the column portion of the mill. The dovetail slide also allows the knee to be raised and lowered as needed. The knee is both supported and moved by a heavy elevating screw mounted inside the knee. The elevating screw is attached to the elevating crank by a geared mechanism, so when the crank handle is turned, the elevating screw rotates and raises or lowers the knee.
The elevating crank contains an adjustable micrometer collar so that the amount of knee movement can be accurately controlled. The locking collar can be loosened and the micrometer colar rotated to set a "0" reference. Then the locking collar can be retightened and the knee moved the desired amount. On most vertical milling machines, each graduation on the micrometer collar equals 0.001" and one full turn of the crank moves the knee 0.100". The knee of the vertical mill provides movement along the Z-axis.
Saddle
The saddle is mounted on another machined dovetail on top of the knee. The saddle permits movement toward and away from the column along the Y-axis. A nut inside the saddle is attached to another heavy screw called a leadscrew. This leadscrew is turned by the saddle crank handle located on the front of the knee. This handle also has an adjustable micrometer collar so that the amount of saddle movement can be accurately controlled. After positioning the saddle, the saddle lock can be used to secure it in place to prevent unwanted movement.
Important: Be sure to release this lock before moving the saddle to prevent damage to the dovetail slide or leadscrew mechanism.
Table
The table is mounted on another machined dovetail on the top of the saddle. The table allows movement from left to right along the X-axis. As with the knee and saddle a leadscrew provides the table movement. This leadscrew is turned by one of two crank handles located at each end of the table to move the table to the left or right. These handles also have adjustable micrometer collars to accurately control movement.
Important: Be sure to release this lock before moving the table to prevent damage to the dovetail slide or leadscrew mechanism.
The table provides a flat reference surface used for locating workpieces for machining operations. T-shaped slots machined in the table accommodate clamping equipment used to secure workpieces or workholding devices for machining. Every effort should be made to protect the surface of the table from damage. When installing heavy devices, such as mill vises, they should always be gently placed on the table. Do not place cutting tools, hammers, files, wrenches, or other rough tools on the machine table.
Turret
The top of the column casting is a machined flat surface. The turret rests on this surface and allows the entire machine head to be swiveled 360 degrees. A protractor on the turret is graduated in degrees and contains a zero mark to position the head in the center of the column. Loosening the clamping bolts allows the turret to be swiveled by pushing on the head.
Ram
The ram allows the entire head to be moved forward and backward and then locked in postion. the movement is provided to increase the workpiece capcaity of the machine. The bottom of the ram contains a dovetail that is fitted to a mating dovetail slot in the top of the turret. The dovetail ensures that the head moves back and forth accurately in a straight line. The ram also contains a rack and pinion gear system. Rotating the ram adjusting lever or nut moves the ram forward and backward.
Head
The head of the mill contains the mechanisms for holding and driving cutting tools. Its basic construction and components are similar to the head of a drill press but with added features
Parts in the Head
Parts in the Head
Spindle
The spindle is a precisely ground shaft. A hole passes through its middle to accommodate various cutting-tool holding devices and the drawbar. The threaded drawbar passes through the spindle from the top of the head. These threads provide a means of securing tools such as drill chucks and collets to the spindle. The top of the drawbar contains a hex for tightening the drawbar into the tool-holding device with a wrench.
The inside diameter of the end of the spindle is tapered for accurately centering tool-holding devices in the spindle. Most modern vertical milling machines use a standard taper known as an R-8 taper. A small key inside the spindle acts as a way to both align tool-holding devices inside the spindle and aid in driving them.
Setting spindle speed
A motor on top of the head rotates the spindle. Most vertical mills have a high/low range lever that controls a msall transmission gear train inside the head. This lever should be placed in the range that corresponds with the desired RPM. Most vertical mill speed ranges are:
low range - 60 to 500 RPM
high range - 500 to 4000 RPM
Important: The lever should only be operated with the spindle is not rotating to avoid damage to the machine head's powertrain.
The RPM can be adjusted in each range by rotating a dial, while the spindle is running, located on the front of the head until the desired RPM is reached.
Spindle brake
The spindle brake lever can be slightly rotated forward or backward to quickly stop the spindle. It can also be pulled out to lock the spindle in place. It is important to remember to release the lock before starting the spindle to avoid excessive wear on the spindle brake mechanism.
Quill
The quill on the vertical mill is much like the quill on the drill press. The quill feed handle can be used when performing holemaking operations or to position the cutting tools for milling operations. A spring inside the head balances the wieght of the quill and helps it to stay where positioned with the feed handle. The micrometer adjusting nut can be set to limit quill travel by moving it so the quill stop comes in contact with the nut. Graduations on the adjusting nut along with those on the front of the head allow for accurate positioning. The quill of the mill provides additional movement along the Z-axis.
Power quill feed
When performing holemaking operations the quill can be set to feed under power. First, the power feed transmission engagement crank located near the upper-right portion of the head must be engaged. Only engage and disengage this knob when the spindle is not running. Most mills have three feed rate settings for the quill feed, 0.0015", 0.003", or 0.006" IPR (inches per revolution).
The feed control lever is located on the left side of the head and is used to start the quill feed. Before beginning quill feed, the spindle must be turned on. The wuill will begin to feed when the clutch is engaged by pulling the handle out.
When using downward poer quill feed, the micrometer adjusting nut can be used to automatically disengage the feed. When the quill stop makes contact with the micrometer adjusting nut, the feed control lever will automatically disengage and quill feed will stop.
7. Lathe
7. Lathe
The metal lathe is designed to support and rotate a piece of material as it is being shaped by a cutting tool. The lathe can produce cylindrical, conical, helical and spherical shapes that are coaxial with the centre line of the lathe.
This type of lathe is often called a centre lathe. Small machines are usually mounted on a bench or a stand and sometimes called bench lathes. Bench lathes are available in various sizes, capable of turning lengths between about 600mm and 1000mm. Larger, heavy duty lathes can turn lengths up to 3 metres or more.
There are two main types of centre lathe. Lathes in which turning speeds are varied using step-cone pulleys are belt driven and are usually called belt-drive head lathes. Lathes that are driven through a gear box are usually called geared head lathes. The drive mechanism of a lathe is contained within the headstock as shown in the diagram below.
In the headstock, a spindle or main shaft is mounted in robust bearings that must are capable of withstanding heavy loads imposed by turning operations and maintaining the accuracy required for the finished job. The main functions of the headstock are to:
Support and rotate the workpieace.
House the speed changing mechanism.
Enable the work holding devices (Chucks) to be attached to the spindle.
The tailstock is made up of two castings. One rests on the guide ways and is clamped to the bed to suit the length of the work. The tailstock spindle or quill is housed in the upper casting which has a sideways adjustment. The tailstock spindle is bored to a standard morse taper to take centres, drill chucks and other attachments.
The carriage is the part of the lathe that supports and controls the movement of the cutting tool. It is comprised of the saddle which fits over and slides on the guide ways and the apron which is fastened to the saddle and hangs in front of the lathe bed. The apron carries the handwheel mechanism for the hand feed as well as the mechanisms for engaging the automatic feed and the lead screw.
Cutting Speed & Machine RPM
Cutting Speed & Machine RPM
Cutting speed is defined as the number of metres of material that passes the lathe tool in one minute, measured around the circumference of the work. Recommended cutting speeds depend on the type of material you are turning and the properties of the cutting tool. For example, Bronze has a faster cutting speed than steel because it is a much softer material. A tungsten carbide cutting tool will enable even higher cutting speeds on the same material compared to using high-speed steel cutting tools.
To achieve the required cutting speed the lathe has to be set to the correct RPM for the diameter of the material. This information can be read from a chart; however, it is useful to know how to calculate RPM when a chart is not available.
Example: Calculate the lathe RPM for rough turning a mild steel bar of 42mm diameter with a high-speed steel cutting tool.
The basic formula for calculating revolutions per minute is: RPM = Cutting Speed/Circumference.
When using a high-speed cutting tool, the cutting speed for rough turning mild steel is 30 metres per minute. Circumference of the bar is calculated as follows:
Circumference of the bar = ℼ x diameter of the bar
= (22/7) x 42mm
= 132mm
RPM = Cutting Speed/Circumference
= (30m x 1000) / 132mm
(Note that the cutting speed 30m per minute is multiplied by 1000 to convert to mm)
= 230 approximately
Centre Drill
Centre Drill
Centre drills are usually double sided drills with a 60' stepped point, held in a drill chuck or collet chuck in a lathe.
The purpose of the centre drill is to create an accurate centre hole in the face of a job so as a live centre can be inserted to support the weight and load of the job, whilst turning it.
Longer jobs generally require a live centre from the tailstock of the lathe to support the job, which prevents chatter and run out.
Centre drills can also be very useful in spotting or starting a precise hole, which will also give a chamfer on the hole; ideally used on the edge of round bar.
Lathe Tools
Lathe Tools
Lathe cutting tools are tools you can use with a lathe machine to produce turned parts and shape materials into the desired shape. There are three major classification categories for lathe cutting tools: material, uses, and method of applying feed.
Cutting edge material is commonly made from high speed steel, but sometimes carbide, tungsten or even diamond is used.
Your tool selection will be determined by the process you wish to complete such as, roughing, finishing, facing, boring, chamfering, knurling or thread cutting.
Chucks
Chucks
Lathe chucks are fitted to the spindle and are used to grip the work. Generally, two sets of jaws are provided with lathe chucks. One set for holding work externally, the other internally. Jaws for a self centering chuck must be fitted with identification amrks corresponding to those on the chuck. They must also be fitted in correct sequence.
The three jaw self centering chuck is made so that the three jaws all move together and are always the same distance from the centre. The three jaw chuck is gennerally used to hold round or hexagonal work.
More information on chucks: four jaw, keyless, scroll
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8. CNC Machines
8. CNC Machines
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