Part 1. Preparation and safety
Objective
- Use a die to repair damaged threads in an automotive component.
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
- Use safety eyewear when using cutting equipment.
- Do not run your fingers down a newly cut thread. It has many sharp edges that will cut your fingers and small metal particles will start an infection in the cut.
- 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
- A die is a metalworking tool used to repair or cut new outside threads on fasteners.
- The die is installed in a tool called a "die stock". It gives the leverage to turn the die over the new thread. The diestock locates the die in place using thumbscrews that match indentations in the outer edge of the die.
- The die has a top and a bottom. The bottom has tapered threads to guide the thread into the die.
- Use a thread cutting compound with the die. It will keep the cutting edge of the die sharp, allowing it to be used many times.
- If cutting a new thread on a bolt or stud, make sure the top of the shank is square. This will help lead the die teeth squarely onto the shank.
- Make sure the die is square to the shaft of the stud or bolt at the start of the thread cutting process.
- When cutting or repairing a thread, once the die has started to cut, turn the die about a quarter of a turn then back off. Cut another quarter of the thread and back off again. Continue until the thread has been cut. This action clears the cutting teeth of any scrap and gives a better finish.
- Once the thread has been cut and the die removed, clean the new thread with a wire brush. This will remove any sharp edges and any left over scrap from the new thread.
- Do not use a wrench to tighten the die locating thumbscrews.
Part 2: Step-by-step instruction
- Determine the thread size
Use a thread pitch gauge to confirm the size of the bolt or stud. This should match the thread it will go into.
- Choose the correct die
Choose the correct size and type of tap and die set for the job. It will be either Inch or Metric.
- Fit the die to the die stock
Fit the die into the diestock, using the locating screw on the stock to engage the hole on the die and secure it into place.
- Apply thread cutting compound
Apply a small amount of thread cutting compound to the exposed, damaged threads of the bolt. If the bolt or stud is a separate item, hold it upright in a vise. Make sure the vise is equipped with soft jaws so you don’t damage the thread any further. Then tighten the vise so that the bolt is vertical.
- Rotate the die stock clockwise
Slowly and carefully turn the diestock in a clockwise direction onto the damaged bolt. Make sure to keep the pressure vertically above the bolt. You will feel the die removing the metal from the bolt. Continue to turn the die until you reach the depth to which the matching nut will be tightened.
- Remove the die counterclockwise
To remove the die, turn the diestock counter-clockwise up and away from the bolt. Clean any filings or particles from the cutting threads of the die.
- Clean and test
Use a rag and then a wire brush to clean the compound and metal particles from the thread of the bolt before you remove it from the vise. Test the job by using the correct size nut and tightening it by hand all the way down the bolt or rod. If the repair is sound, dismantle the die from the diestock, clean them both and put them away safely.
Part 1. Preparation and safety
Objective
- Use a tap to repair damaged threads in an automotive component.
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
- Use safety eyewear when using cutting equipment.
- The teeth of a tap are sharp. Be careful when handling the tap so that you do not injure yourself.
- 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
- There are three different types of thread taps: starting, intermediate and finishing.
- A starting tap has a well tapered end, which is why it is sometimes called a "taper" tap. This allows the tap gradually to cut deeper threads as it passes through the job. It can be used to cut a thread in work that has a thin enough section to allow the tap to pass through it. It is also used to perform the first cut in a blind hole.
- An intermediate, or second tap is used for the second cut in a blind hole. It has fewer tapers than a tapered tap, which allows the threads at the bottom of the hole to be more complete.
- A finishing, bottoming or plug tap is designed to cut the final thread into a blind hole. It has almost no taper, so the threads it cuts extend to the bottom of the hole.
- Use a thread cutting compound with the thread tap. It will keep the cutting edge of the tap sharp, allowing it to be used many times.
- When cutting a new thread into a hole, make sure the tap is square to the work piece. This will help lead the teeth to cut squarely onto the shank.
- When cutting or repairing a thread, once the tap has started to cut, turn it about a quarter of a turn then back off, then cut another quarter thread and back off again. Continue until the thread has been cut. This action clears the cutting teeth of any scrap and gives a better finish.
- Once the thread has been cut and the tap removed, clean the new thread with an air duster.
- Do not use an impact wrench on the tap.
- Practice on a scrap component before attempting a real one.
Part 2: Step-by-step instruction
- Choose the correct tap
Choose the correct size and type of tap you need to repair the thread, either in Metric or Inch.
- Determine the thread size
Determine the thread size of the screw that should fit the damaged hole. Use a thread pitch gauge to confirm the size.
- Select corresponding tap
Select the corresponding tap size and type: either a taper, intermediate or bottoming tap.
- Fit the tap to the tap wrench
Select either a T-handle wrench or a hand-held tap wrench, and fit the square end of the tap shank into the chuck on the wrench then tighten the chuck.
- Apply thread cutting compound
Apply a small amount of thread cutting compound to the cutting teeth of the tap. Position the tap in the damaged hole, making sure that it’s square to the hole and not at an angle.
- Rotate the tap clockwise
Slowly and carefully turn the tap wrench in a clockwise direction into the damaged hole. You will feel the tap removing the metal from inside the hole, making the thread. Continue to turn the tap until it has bottomed in the hole or has passed all the way through.
- Remove the tap counterclockwise
To remove the tap, turn the wrench counter-clockwise up and out of the hole. Clean any filings or particles from the cutting threads and the flute of the tap before you remove it from the wrench.
- Clean out the hole and test it
Clean out any filings or particles from the hole you have just repaired. You can then test the repair by using the correct size screw or bolt and tightening it by hand. Sometimes you’ll find the damage was so severe that the tap wrench procedure fails to fix the problem. If this happens refer the job to your supervisor.
Removing a stud
Part 1. Preparation and safety
Objective
- Remove and replace a stud with a jam and drive nut or a stud remover.
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
- Do not apply too much force to old and corroded studs. They may break if too much force is applied to 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
- Studs can be removed and refitted using two different methods:
- Jam and drive nut
- Stud remover
- The jam and drive nut method is used when the stud is re-used because it does not damage the stud.
- Stud removers are used to remove damaged studs when jam and drive nuts cannot perform the task.
- The most common type of stud remover consists of a frame with two holes and a knurled offset movable set of jaws.
- The holes are two different sizes. When you slide the stud remover over the stud, select the hole that allows the jaw to have the best purchase.
- Measure the exposed length of the existing stud before removal.
- After the stud has been removed, compare it to the new one. They should be the same thread and pitch.
- When fitting the new stud, apply the correct thread coating compound. It may be thread locking compound or an anti-rusting agent.
Part 2: Step-by-step instruction
- Use penetrating fluid
If the stud is rusted in place, soak the base of the stud threads with penetrating fluid to remove the corrosion and make it easier to take out. If possible, let the penetrating fluid soak in overnight.
- Measure the old stud
Before working on the old stud, measure its exposed portion to verify the new stud is the same size. Note the measurement.
- Install the ‘drive’ nut
Find two nuts with the same size and thread as the old stud, and thread one of these all the way down to the bottom of the stud. This will be the ‘drive’ nut.
- Install the ‘jam’ nut
Thread the second nut all the way down until it sits on top of the drive nut. This second nut will be the ‘jam’ nut.
- Tighten the 'jam' nut
Secure an open-end wrench to the bottom “drive” nut and hold it in position. Then tighten the “jam” nut against the “drive nut” with a box or open-end wrench. The jam nut will now prevent the drive nut from moving.
- Turn the ‘drive’ nut
Use the open-end wrench to turn the bottom drive nut counter-clockwise. The drive nut applies the turning force to the stud and forces it to unscrew.
- Remove the stud
Continue to rotate the drive nut until the stud comes out.
- Attach the stud remover
If jam and drive nuts don’t budge the stud, you can use a stud remover. Slide the stud remover over the old stud and seat it flush with the surface of the component. Turn the jaws in a counter clockwise direction until the stud is held tight.
- Turn counterclockwise
Fit a wrench onto the stud remover and turn the wrench in a counter-clockwise direction. The stud remover will grip the stud and turn it. Continue to rotate the stud, using the wrench, until the stud comes out.
- Inspect for damage
Once you’ve removed the old stud, inspect the internal thread of the hole for any damage
Using a screw extractor
Part 1. Preparation and safety
Objective
- Use a screw extractor to remove a broken stud or screw.
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
- Always wear eye protection when drilling and removing a broken stud or bolt.
- 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 can fail for many reasons: over-tightening, over-stressing, fatigue and old age are all possible causes.
- If the fastener is broken near the surface, a screw extractor will be needed to remove it.
- Screw extractors are available in two common types: One has reverse threads and the other has straight flutes.
- The fastener needs to be drilled before the screw extractor can be inserted.
- Always drill to the size recommended by the screw extractor instructions. If you are unsure of the correct size, ask your supervisor.
- If a fastener is rusted into place, use a penetrating fluid on the threads and allow it time to work before attempting to loosen it.
- Sometimes the fastener can be made easier to remove by the application of heat to the surrounding area. Ask your supervisor to demonstrate this to you.
- When fitting a replacement stud, apply the recommended coating to the thread. It may be thread locking or anti-seize compound. Follow the manufacturer's instructions on the application and use of the compound.
- Use a jam and drive nut to fit the replacement stud.
Part 2: Step-by-step instruction
- Select the correct tools for the job
Open your screw extractor set and study the instructions, which should be enclosed. Identify and select the correct size drill and screw extractor for the job.
- Mark the exact center
With a center punch, mark the exact center of the broken screw to get the power drill started.
- Drill a hole
Drill a hole through the center of the bolt. Drill only to the depth specified in your screw extractor instructions.
- Select the correct size
Make sure you use the correct screw extractor – that is, the one that matches the drill bit you used.
- Turn extractor counterclockwise
Because the screw extractor has reverse threads, you will need to remember to turn it counter-clockwise.
- Use a tap wrench
Use a tap wrench and turn the screw extractor into the hole. The reverse threads will force the extractor into the hole until the broken bolt or stud is forced to turn. Continue turning until the stud is removed.
Using a gear puller
Part 1. Preparation and safety
Objective
- Select, install and use a gear puller to remove a pulley.
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
- Always wear eye protection when using a gear puller.
- Make sure the puller is located correctly on the work piece. If the jaws cannot be fitted correctly on the part, then select a more appropriate puller. Do not use a puller that does not fit the job.
- 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
- Gear and bearing pullers are designed for hundreds of applications. Their main purpose is to remove a component, such as a gear, pulley or bearing from a shaft, or to remove a shaft from inside a hole. Normally these components will have been pressed on to that shaft, or into the hole, so they will need considerable force to remove them.
- Gear pullers come in a range of sizes and shapes, all designed for particular applications. They will consist of three main parts:
- Jaws
- Cross Arm
- Forcing Screw
- There will normally be two or three jaws on a puller. They will be designed to work either externally around a pulley, or internally.
- The forcing screw is a long, fine threaded screw that is applied to the center of the shaft. When the forcing screw is turned, it applies many tons/tonnes of force through the component you are removing.
- The cross arm attaches the jaws to the forcing screw. There may be two, three or four arms. If the cross arm has four arms, three of the arms will be spaced 120-degrees apart. The fourth arm will be positioned 180-degrees apart from one arm. This allows the cross arm to be used as either a two- or a three-arm puller.
Part 2: Step-by-step instruction
- Examine the gear puller
Examine the gear puller you have selected for the job. Identify the jaws – there may be two or three of them, and they must fit the part you want to remove. The cross-arm enables you to adjust the diameter of the jaws. The forcing screw should fit snugly onto the part you’re removing. Finally, select the right size wrench to fit the nut on the end of the forcing screw.
- Adjust and fit the puller
Adjust the jaws and cross-arms of the puller so that it fits tightly around the part to be removed. The arms of the jaws should be pulling against the component at close to right angles.
- Position the forcing screw
Use the appropriate wrench to run the forcing screw down to touch the shaft. Check that the point of the forcing screw is centered on the shaft. If not, adjust the jaws and cross-arms until the point is in the center of the shaft.
- Tighten the forcing screw
Tighten the forcing screw slowly and carefully onto the shaft. Check that the puller is not going to slip off center or off the pulley. Readjust the puller if necessary.
- Remove the part
If the forcing screw and puller jaws remain in the correct position, tighten the forcing screw and pull the part off the shaft.
