Part 1. Preparation and safety
Objective
- Use a torque angle gauge in conjunction with a torque wrench.
Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection – such as rubber gloves and barrier cream
- Respiratory equipment – such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
- Refer to the manufacturer's specifications when tightening fasteners.
- If replacing a fastener, make sure it has the correct tensile value for the task it has to perform.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Over-tightening a fastener can damage the gasket and the threads.
- Support the head of the torque wrench during its use.
- Vehicle manufacturers specify torque values for certain fasteners. This is to make sure that fasteners are not over- or under-tightened.
- The torque value will be specified in foot-pounds (lb-ft) or Newton-meters (Nm) and is the amount of twisting force applied to a fastener by the torque wrench.
- A foot-pound is described as the amount of twisting force applied to a shaft by a lever one foot long with a weight of one pound placed on the outer end. A torque value of 100lb-ft will be the same as a 100 lb weight placed at the end of a 1-foot-long lever.
- A Newton-meter is described as the amount of twisting force applied to a shaft by a lever one meter long with a force of one Newton applied to the outer end. A torque value of 100Nm will be the same as applying a 100 Newton force to the end of a 1-meter long lever.
- One lb-ft is equal to 1.35 Nm.
Torque wrench
- The torque wrench is used to apply a specified amount of torque to a fastener.
- There are various methods used by torque wrenches to indicate that the correct torque has been reached. Some will give an audible signal such as a click or a beep, while others will give a visual signal such as a light or a pin moving or clicking out.
- Make sure the threads are clean before tightening the fastener to a specified torque. Any friction will give an inaccurate reading and will affect the compressive force the fastener will apply to the component.
- Always handle a torque wrench carefully. It is a precision instrument that will lose its calibration if mistreated.
Torque angle gauge
- The torque angle gauge is used to make sure there is equal tightness of fasteners on a component. It is calibrated in degrees.
- Tightening by angle rather than torque removes the error that is produced by friction in the threads.
Torque to yield (also known as torque and turn)
- Some fasteners are designed to be deliberately over-tightened. These bolts are known as "torque to yield" bolts. The fastener is tightened to a specific torque with a torque wrench, then the torque angle gauge is turned a number of degrees.
- When tightened, these fasteners are stretched beyond their elastic limit. So when they are removed, they must be discarded and replaced with new ones.
Part 2: Step-by-step instruction
- Check the specifications
Determine the correct torque value for the bolt or fastener you’re using. This will be in Foot-Pounds or Newton Meters. Also, check the torque angle specifications for the bolt or fastener.
- Tighten the bolt
Tighten the bolt to the specified torque.
- Install the gauge
Install the torque angle gauge over the head of the bolt, and then put the torque wrench on top of the gauge.
- Torque to specifications
Turn the torque wrench the specified number of degrees for that bolt. If the component requires multiple bolts or fasteners, make sure to tighten them all to the same torque value and torque angle.
Part 1. Preparation and safety
Objective
- Identify the common types, length, diameter, grade and thread pitch of threaded fasteners.
Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection – such as rubber gloves and barrier cream
- Respiratory equipment – such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
- Never use a bolt that has been over-tightened. Its tensile strength is very low and it could break.
- Use the correct tool to tighten or loosen bolts, otherwise you could break them.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Fasteners are used to secure components or pieces of components together. There are two main types of fasteners: inch and metric. They are not compatible.
- Bolts are identified in four ways:
- Length
- Diameter
- Thread Pitch
- Tensile Strength
- A bolt’s length is the distance from under the head of the bolt to the far end of the thread. Inch bolts can come in sizes such as 1 1⁄4", 3 1⁄2", etc. Metric bolt sizes might be 25mm, 40mm, etc.
- The bolt diameter is the thickness of the bolt shank. This will be 1⁄4" or 1⁄2", etc if it is an inch bolt, or 6mm, 8mm, 10mm, etc if it is a metric bolt.
- Fine threads can achieve a greater tightening force than coarse threads.
- Coarse threads are used in softer materials because they have a greater grip on the material.
- The measurement of thread pitch for UNC and UNF bolts is described in the number of threads-per-inch (TPI).
- A UNF bolt may measure 1⁄2" x 3" x 20. That is, the bolt is 3" long, has a shank diameter of 1⁄2" and the threaded area has 20 threads in every inch of thread. A UNC bolt that measures 1⁄2" x 3" x 13 will have the same dimensions but have only 13 threads for every inch of thread.
- The length and shank diameter of metric bolts is measured in the same way as UNF and UNC bolts but the measurements are in millimeters, rather than in inches or fractions of an inch. The difference lies in how the thread pitch is measured. Metric bolts define their pitch by the distance between each thread. There are still fine and coarse threads but this time the bolt dimension may be 6mm x 40mm x 1.0 or 1.25 in the case of a fine thread. A coarse threaded bolt of a similar size will have the dimensions of 6mm x 40mm x 1.75 or 2.0.
- The suitability of a bolt for an application is determined by its tensile strength and its yield strength. The tensile strength is defined as the maximum stretching stress a bolt can withstand without breaking. The yield strength is the maximum stress a bolt can withstand and still return to its original form.
- There are two standards of bolt grading in use. The Society of Automotive Engineers (SAE) and the American National Standards Institute (ANSI) apply the ANSI standard. This grading applies to the strength of the bolt. The second is the International Standards Organization (ISO) grading for tensile strength and yield strength of the bolt.
- A bolt graded by the ANSI standard is identified by the number of lines arranged around the head of the bolt. The minimum value of tensile strength is defined as 2. A bolt of this value has no lines on its on its head.
- 0 lines = Grade 2 tensile strength
- 3 lines = Grade 5
- 5 lines = Grade 7
- 6 lines = Grade 8
- A high grade-value = a high tensile value.
- The ISO standard uses two numbers on the head of the bolt. The first number indicates the tensile strength; the second number signifies the yield strength.
- If a bolt is marked 8.8, it has a tensile strength of 800 MegaPascals (MPa) and a yield strength value of 640 MPa, 80% of its tensile strength. A marking of 10.9 indicates a tensile value of 1000 MPa with a yield strength of 900 MPa, 90% of its tensile strength.
- 4 = 400 MPa
- 5 = 500 MPa
- 8 = 800 MPa
- 10 = 1000 MPa
- .5 = 50%
- .6 = 60%
- .7 = 70%, etc.
- Always use a bolt suitable for the application. If a bolt with too high tensile strength is used and not tightened to its designed value, it may fail. That is because high tensile bolts have less resistance to fatigue than bolts with a lower tensile value.
Part 2: Step-by-step instruction
- Choose a pitch gauge
To determine the thread pitch of a particular fastener, you need to use a thread pitch gauge.
- Check gauge markings
Open out the pitch gauge set and examine the markings on the toothed blades. The markings will be either in inch units or in metric units. The numbers stamped on the toothed blade of an inch gauge set indicate the number of threads per inch of thread length. For example: 16 threads to the inch. Look at the numbers on the blade of a Metric pitch gauge set. The numbers indicate the width between each thread in millimeters. For example: a thread pitch of 1.5 millimeters.
- Measure a known size
Choose a fastener of a size you know. Say, 3/8inch U-N-C bolt. Using your inch gauge set, select each blade and hold the toothed edge against the thread of the bolt. Continue trying the blades until you find one that matches exactly the thread on your bolt. Check the number on the blade; it should read 16. That is, 16 threads per inch.
- Measure an unknown size
Now choose a fastener whose size you do not know. If it is a metric bolt, select the metric thread pitch gauge. Repeat the procedure with the blades against the thread of the bolt, until you find a perfect match. Check the number on the blade; it will tell you the thread pitch of this fastener in millimeters.
- Correctly store gauge
When you have finished, be sure to fold all of the blades back into their casing before putting the gauge set away. This is to protect the blade teeth from damage.
Part 1. Preparation and safety
Objective
- Connect and use a vacuum gauge to check engine manifold vacuum.
Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection – such as rubber gloves and barrier cream
- Respiratory equipment – such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Vacuum gauges are possibly the most useful diagnostic tool in engine diagnosis. They are often forgotten by technicians who may prefer to use modern electronic diagnostic equipment.
- A vacuum gauge is used to measure the manifold pressure. In naturally aspirated engines, this pressure is always below atmospheric pressure. It is referred to as a vacuum.
- The vacuum gauge reads in either millimeters of mercury (mm Hg) or inches of mercury (in Hg). Those measurements mean the vacuum is strong enough to support a column of mercury in a tube to a height of so many millimeters or inches.
- 0 in Hg is equal to atmospheric pressure. A fully loaded engine at wide-open throttle will reach close to this reading.
- 30 in Hg is referred to as a perfect vacuum. It is a point where there is no pressure at all. It is a theoretical number because it is impossible to achieve. An engine decelerating on closed throttle will reach close to this reading.
- Healthy engines will create more vacuum in their inlet manifolds than worn engines. So a pressure comparison between a known healthy reading and the engine you are testing can assist in determining the state of wear of the engine.
- Refer to the chart below for various vacuum gauge readings.
| Engine Speed | Gauge Reading | Engine Condition |
| Idle | 16" - 22" steady | Healthy |
| Idle | 14" - 20" steady | Fair but worn |
| Snap throttle | Jumps to 2" then on decel moves to 25" | Healthy |
| Snap throttle | Jumps to 1" then on decel moves to 22" | Fair but worn |
| Idle | 8" or less | Vacuum leak, loose intake manifold |
| Idle | Fluctuated between 14" - 19" | Worn valve guides or head gasket blown between 2 cylinders |
| Idle | Reading drops from normal | Burnt valve, valve stuck open, misfiring spark plug |
| Idle | 8" - 14" | Valve timing incorrect or large camshaft overlap |
| Idle | 14" - 16" | Ignition timing wrong |
| Idle | Moves between 12" - 16" | Idle mixture incorrect |
| Slow engine speed rise | Needle falls then rises suddenly | Blocked exhaustWeak valve springs |
| 3000 rpm | Needle fluctuates and worsens with higher rpm | Weak valve springs |
Part 2: Step-by-step instruction
- Examine the gauge
The vacuum gauge has many uses in vehicle maintenance but its importance in detecting leaks or diagnosing problems is often overlooked. Examine the vacuum gauge that’s used in your workshop. Determine the units of measurement. And be sure to read the printed instructions that accompany the gauge.
- Fit the gauge to the manifold
In this case, the vacuum gauge will be used to measure manifold vacuum. Fit the vacuum gauge onto the engine intake manifold. You may need to fit a “Tee” piece to an existing vacuum connection.
- Start the engine
With the vehicle in neutral or park, and the emergency brake on, start the vehicle’s engine and let it settle into a uniform idle.
- Check the reading
Check the reading on your vacuum gauge. If the engine has no problems, the reading should be within the range fourteen to twenty- two inches of mercury and the needle steady.
- Change the load on the engine
Snap the throttle open and let it close. You will see the vacuum gauge needle quickly move to near zero then move all the way to almost thirty inches then back to the idle position. Open the throttle slowly. Notice the reaction of the needle.
- Record your observations
Make sure you keep a record of the readings and needle movements you experience when working with different engine components.
