Part of Unit: Tools, Equipment Identification and Utilization
Lesson Plan Overview / Details
The instructor will demonstrate the need, theory, key terms and techniques of broken bolt extraction. At the end of the lesson, students will demonstrate the ability to name 6 broken bolt extraction methods.
- One class period of
- 57 Minutes
- 0 Minutes
- 0 Minutes
California Career and Technical Education Standards
- T.C.C1.5 Use appropriate personal protective equipment and safety practices.
- T.C.C2.1 Understand and use appropriate tools and equipment, such as wrenches, sockets, a...
- T.FS.5.1 Apply appropriate problem-solving strategies and critical thinking skills to wor...
- T.FS.5.3 Use critical thinking skills to make informed decisions and solve problems.
- T.FS.5.5 Understand and demonstrate the ability to plan and solve problems in a systemati...
California Academic Content Standards (Reinforced)
Objectives and Goals
- Students will understand and use appropriate tools and equipment, such as punches, easy-outs, and left hand drill bits, to extract broken bolts.
- Students will use appropriate personal protective equipment, such as eye and ear protection, and appropriate safety practices, such as proper dress in a shop environment.
- Students will apply appropriate problem-solving strategies and critical thinking skills to work-related issues and tasks, by choosing the correct extraction tool based on the specifics of various broken bolt scenarios.
- Students will use critical thinking skills to make informed decisions and solve problems, such as how hard to push down when turning the extraction tool.
- Students will understand and demonstrate the ability to plan and solve problems in a systematic manner and apply the learned skills to real-world situations, such which size extractor, drill bit and punch to use on a particular bolt.
- Students will show up on time.
- Students will follow instructions and procedures common to all detailed shop work and production processes in order to create a specific solution to a problem.
Activities in this Lesson
Each day, when students enter the classroom, I usually have a warm up question projected on a video screen, but you could write it on the board. At the beginning of the week students grab a new blank warm up work sheet, which I have created for them, which students keep in a folder in their back packs. Students complete all the warm ups for the week on that sheet and turn in their sheet to me at the end of the week for grade points.
Also, under the daily warm up question, I have an outline of our activities for that day.
As students enter I wait for them to take their seats, I ask them to take out their warm up work sheets, then I call their attention to a shop dilemma that I would like them to address.
Using a video camera which projects on the classroom projection screen, I will bring their attention to an 8mm intake or exhaust manifold bolt on the side of a cylinder head that I have on a bench in the classroom. I am trying to loosen the bolt, but in reality I will be tightening it. The bolt will eventually break. (You could also produce your own video of the same thing and show that to them. You could also demonstrate bolt breaking without any media, by simply acting it out in front of the class, and showing them the head of the bolt after you break it off.)
After breaking the bolt, I ask students to:
- consider what mistake was made that caused the bolt to break
- compose an answer to the question on their warm up work sheet
- they may discuss the question with their neighbors
After about five minutes, I call on students to share their answers with the class. As students, give their answers, I repeat their answers out loud. I will also call on non volunteers. After a few minutes, I take about five minutes to comment on the scenario, explaining what caused the bolt to break.
- Bolt Extraction Tools Lecture
I pass around examples of "easy-outs," center punches, left hand drill bits, etc. As students are handling the tools, I have a list of key terms and tool names on the video screen. I pronounce the terms and names of each tool aloud. I explain how each tool is used, in what order the tools are used, and when you might choose one tool instead of another. I also begin to explain that judgements need to be made at each step of the process, in order to deal with various scenarios that students may encounter.
I will mention that there are articles and information on the web about removing broken bolts. I will have the web page "The Art of Extraction" on the screen behind me, as an example, or write the title of the article on the board.
Resources and Materials
- The Art of Extraction [ Go to Site ] Article about removing broken bolts
- Methods and Techniques of Broken Bolt Extraction Demo / Modeling
Using a video camera projecting the image on a screen behind me (or simply demonstrating without a video image), I begin removing the broken bolt using a typical series of steps.
At this time, put on your safety glasses. Have any students in the front row/s put on safety glasses. If the drill is loud, have students put on ear protection. Point out the importance of having long hair tied back, and of securing or removing loose clothing or jewelry.
Method A: Vise Grips and Penetrating Oil
Explain that, if a piece of the bolt is sticking up above the surface, you can try to grab it with some vise grips, and twist it out that way. Try soaking it with some penetrating oil first.
Demonstrate using this method. Explain how to adjust vise grips properly, and how to orient the jaws in the right direction to increase mechanical advantage, but don't remove the bolt with this method. Save that for the "easy out" method.
(Note: I usually don't demonstrate the next two methods because many students in a real world setting will not have access to a torch or a welder to perform these techniques, and because the easy out mentioned in this lesson will usually work just as well.)
Method B: Vise Grips and Heat
Explain that by using a propane or acetylene torch to heat the bolt, then letting it cool, and then striking it with a hammer, it can sometimes make the "vise-grip" method work better.
Method C: Creating a New Head
Explain that you can weld an appropriate size washer on the broken piece, then weld an appropriate size nut onto the washer. After that, you can sometimes twist the bolt out with a wrench or socket.
Method D: Left Hand Drill Bits
If vise grips don't work, cut or grind off the piece that's sticking up (make it as flat as possible), or if it originally broke flush or below the surface, take out an appropriate size punch and ball peen hammer.
Demonstrate how to properly make a punch mark in the center of the bolt. Emphasize the importance of getting it as close as possible to the center. Tell them they can us a centering block, if possible.
Tighten a small (1/8th inch) diameter left hand drill bit into a (preferably) low speed, high torque drill. Demonstrate how to drill a pilot hole in the bolt. Emphasize the importance of putting the drill in reverse mode, and of going in straight. Use a centering block, if possible.
Explain that by using the next larger bit size, it will hopefully jam in the hole and twist the piece out, because the bits are left hand style.
Don't remove the bolt with this method. Save that for the easy out method.
Method E: Right Hand Drill Bits and Easy Outs
Using the hole that you made with the left hand bit, pick an appropriate size easy out, place it in a T-handle holder, tap the easy out with the hammer, and begin pushing and rotating counterclockwise to remove the broken piece. Explain that easy outs can be used with right hand drill bits, which are more common.
You may remove the piece at this stage, if possible.
Pass the piece around the classroom or the shop, so students can see the finished product.
Method F: Drilling Out the Piece Completely
I usually don't demonstrate this method, but it's a good time to mimic the actions of using incrementally larger bits to drill all the way through the broken piece until all that remains is the threads, at which time students can use a pick or a die to remove the threads and the remaining pieces. Emphasize the importance of not drilling into sensitive areas below the bolt, as well as the importance of drilling straight and through the center.
Also, point out the importance of not breaking off a drill bit or easy out in a bolt, because these objects are made of hardened steel and are very difficult to drill through. At that point, only a machine shop will have the special equipment necessary to remove the broken bit or easy out.
Take appropriate questions throughout the demonstration. Ask for questions at the conclusion of the demonstration.
I clean the work area and inform the students that during the next class meeting they will have the opportunity to do their own bolt extraction in the shop/lab.
- Pop Quiz Assessment
I have students return to their desks, if they are not already there. Each student gets a piece of 4" x 5" scratch paper. They must put their name at the top and write down the title of all 6 extraction methods before they can leave the classroom. They must right legibly.
I collect a completed quiz from each student. After that, I will say, "Okay, so what are the 6 methods?" As students are shouting out answers, I repeat them and count on my fingers until we get to all 6.
- Assessment Types:
- Teacher-Made Test,
Before the next class meeting, I review student quiz responses, and identify students who have gaps in their learning, and review steps and procedures to increase student performance. In the next lesson during their guided practice, I will seek out those students who performed poorly on the quiz and remediate/modify instruction.
- Broken Bolt Extraction by Robert Thayer.doc [ Download ]