Activity 001: Workholding Methods Comparison Lab

Activity ID: U4M3-ACT-001 Duration: 45 minutes Objective: Students will set up and evaluate three different workholding methods on the CNC router, measuring hold strength and identifying appropriate applications for each. Group Size: 3 students

Overview

Each group will secure identical pieces of material using mechanical clamps, double-sided tape, and screws, then evaluate each method for hold strength, setup time, toolpath accessibility, and material compatibility. This comparative approach builds practical judgment for real-world workholding decisions.

Materials & Equipment Needed

• CNC router (powered off for setup phases)
• 3 pieces of ¾" MDF, each 12" × 12"
• Toe clamps with T-slot hardware (2-4 clamps per setup)
• Double-sided carpet tape (2" wide)

• 10 wood screws with fender washers (6 per setup)

• Spring scale or fish scale (for pull testing)
• Stopwatch
• Setup evaluation worksheet
• PPE: Safety glasses

Instructions & Procedure

Phase 1: Mechanical Clamp Setup (12 minutes) 1. Place the first MDF piece on the spoilboard 2. Start the stopwatch — record setup time 3. Position 4 toe clamps around the perimeter, leaving a 10" × 10" interior clear zone for cutting 4. Tighten all clamps securely 5. Stop the timer — record setup time 6. Perform pull test: attach spring scale to the center of the material, pull horizontally. Record the force at which the material begins to shift (or note "did not shift" at maximum scale reading) 7. Evaluate: What percentage of the material surface is accessible for cutting? Where are the "no-go zones" for the toolpath? 8. Remove clamps and set the piece aside

Phase 2: Double-Sided Tape Setup (12 minutes) 1. Clean the spoilboard surface with isopropyl alcohol where the material will sit 2. Start the stopwatch 3. Apply 4 strips of carpet tape to the bottom of the second MDF piece, running parallel, covering approximately 50% of the surface 4. Press the material firmly onto the spoilboard — apply weight or roller pressure for 30 seconds 5. Stop the timer — record setup time 6. Perform pull test: attach spring scale, pull horizontally. Record force at which material shifts 7. Evaluate: What percentage of the material surface is accessible for cutting? Are there any no-go zones? 8. Carefully pry up the material (putty knife at corner) and clean tape residue

Phase 3: Screw-Down Setup (12 minutes) 1. Start the stopwatch 2. Place the third MDF piece on the spoilboard 3. Mark screw positions: 4 corners at 0.5" from each edge, plus 2 additional screws centered on the long edges 4. Pre-drill through the MDF and into the spoilboard 5. Drive #10 screws with fender washers at all 6 positions 6. Stop the timer — record setup time 7. Perform pull test (same method) 8. Evaluate: accessible cutting area, noting screw head positions relative to potential toolpaths 9. Remove screws

Phase 4: Comparison & Discussion (9 minutes) 1. Complete the comparison table on the worksheet:

Criteria	Clamps	Tape	Screws
Setup time	___ min	___ min	___ min
Hold force (lbs)	___	___	___
Accessible area (%)	___	___	___
Reusability	___	___	___
Cost per setup	___	___	___
Best material type	___	___	___

1. Discuss as a group: When would you choose each method?
2. Present findings to the class (1-2 minutes per group)

Discussion Points

• Which method provided the strongest hold? Was it also the fastest to set up?
• For a production run of 20 identical parts, which method would be most efficient?
• How would your choice change for ⅛" acrylic vs. ¾" plywood vs. 2" hardwood?
• What hybrid combinations might work better than any single method?

Expected Outcomes

• Students can set up all three workholding methods independently
• Students understand the trade-offs between hold strength, setup time, and accessibility
• Students develop judgment for selecting appropriate workholding based on job requirements

Assessment Rubric

Criteria	Excellent (4)	Proficient (3)	Developing (2)	Beginning (1)
Setup Execution	All methods set up correctly and efficiently	Methods set up correctly with minor issues	Setup requires significant assistance	Cannot set up workholding independently
Measurement Accuracy	Consistent, well-documented measurements	Reasonable measurements with minor gaps	Inconsistent measurements	Missing or unreliable data
Analysis Quality	Insightful comparison with practical recommendations	Good comparison covering key factors	Basic comparison missing important factors	No meaningful comparison
Safety Awareness	Follows all safety procedures, identifies hazards	Follows procedures with minor reminders	Needs frequent safety reminders	Safety awareness lacking

Safety Considerations

• Machine must be powered off and locked out during all setup phases
• Wear safety glasses when driving screws (risk of shattered screw or flying debris)
• Be careful with sharp edges on metal clamps
• When removing taped material, use a putty knife — do not pry with fingers
• Screws that hit hidden metal in the spoilboard can shatter — wear glasses

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Last Updated: 2026-03-19