California Career and Technical Education Standards

• BTC.A.A2.1 Use common hand tools and accessories, such as planers, shapers, clamping and gr...
• BTC.A.A6.2 Use hand tools (wood chisels, drills, coping saws) and power tools (routers, san...

California Academic Content Standards (Reinforced)

• ELA.8.R.CAGT.2.5 Understand and explain the use of a complex mechanical device by following techn...3
• M.5.NS.2.5 Compute and perform simple multiplication and division of fractions and apply th...1
• M.6.NS.2.2 Explain the meaning of multiplication and division of positive fractions and per...1

• Break a joint - Hooks / Set

  Teacher pre-makes two joints -  one dado and one butt. Both joints are glued together with a weak glue concentration.

  Pass out the prediction sheet. Have the students look at the joints and choose which joint will break first and to guess how much force it will take to break the joints.

  Using a hydraulic jack and bath scale, break each joint. Teacher will take a joint and place it in the jig. Then place a hydraulic jack on a bath scale and place it under the joint. A student will be pumping the jack. Another one will be reading off the scale reading in units of five.  

  Have students turn in their papers as a form of assessing th e ir understanding.

  Talk to the students about why the dado is stronger than the butt joint. Give samples of items that use dado joints.

  • Dog - Front View [ View Image ] [ Download Original ]
  • Dog - Side View [ View Image ] [ Download Original ]
  • Dog - Exploded View [ View Image ] [ Download Original ]
  • Jig [ View Image ] [ Download Original ] null
  • Prediction sheet [ Download ] null
• Discussion of joints - Lecture

  Teacher passes out the demo worksheets and shows each tool for making the dado. Back saw, paring chisel, combo square, project drawings and pencil. Students will write down the tool names on their worksheet as the teacher points them out.

  Teacher will ask student what they think the dado joint could be used for. After input, the teacher explains it is used for shelves, boxes, homes. They write this on their worksheet.

  • Step by step worksheet [ Download ]
• How is it made - Demo / Modeling

  Teacher demonstrates how to make the joint. At each stage students will write down the step on their worksheets. Each time the teacher picks up a tool he asks what its name is . Teacher will be using an  8” piece of wood.

  Teacher says:

  Look at your drawing. Point to the dado joint. What is the length of wood?

  Step 1: From the end of the wood measure over 2 ½” using your combination square to mark all the way around the wood.

  Teacher should review how to use a combo square properly

  Step 2: “What is half of 1 ½ ?” From the same end of the wood measure over 1 ¼ and mark all the way around. This is the center of the dado.

  Step 3: “Look at the drawing. How wide is the dado?” What is half of 1 ¼ “. From center line measure over 3/8” on each side. Mark all the way around.

  Step 4. “Look at the drawing, How deep is the dado cut?” Using your combo square set it to 1/4” and mark each sides depth. 

  Step 5: “Using your backsaw cut both shoulders down to depth”

  Teacher demos how to hold a backsaw, split the line during cut, and cut a straight line.

  Step 6: “Using your paring chisel, chisel out your joint.”

  Teacher demos how to use the chisel. Demo how to chisel with the grain and work to the centers. Demo how do fine shavings and fit the joint. Review that they need two clamps to hold down the wood and basic chisel safety.

  Step 7: “ From the other end of the wood make a second dado joint” “the cut off both pieces.”

  Teacher demo how cut through the wood and not cut into the table.

  • Dog drawing [ Download ]
• Time to build - Guided Practice

  Give the students an 8” piece of wood and have them make two dado joints. Teacher will walk around the shop watching and helping students finish the joint. Teacher may need to do review with some students on proper safety that was covered in past lessons.
• On your own - Independent Practice

  Student that finish early will make a dado out of oak. Or they will make a rabbet on new wood. Have them go home and make a list of all the rabbets they see.