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.
Source: CDX Global
