Phase 2: Make it Fit

"The difference between a cool shape and a useful tool is 0.2mm of tolerance."

What You'll Learn

Now things get practical. You're moving beyond "look what I made!" to "look what I solved." This phase is all about designing parts that interact with the real world—clips that grip cables, hooks that hang on specific shelves, holders that fit exact spaces.

You'll discover that measuring is everything, that "close enough" usually isn't, and that test prints are your best friend. This is where you learn that Version 1 is always a prototype, and that's perfectly fine. Iteration isn't failure—it's how real makers work.

Core Skills

• [ ] Measure real objects accurately with a ruler (eventually calipers)
• [ ] Understand tolerances: add 0.2-0.5mm gap so parts fit without forcing
• [ ] Design test pieces (print just the critical part first, not the whole thing)
• [ ] Create holes, slots, and clips that match real-world objects
• [ ] Use basic CAD operations: align, group, mirror, duplicate
• [ ] Label your file versions (v1, v2, v3) and track what changed
• [ ] Calculate print time vs. test time tradeoffs

Suggested Projects

1. Cable Clips for Dad's Office - Measure cable thickness, design a clip that snaps onto desk edge and holds cables. Teaches tolerance and functional clips.

2. Custom Shelf Hooks - Measure a shelf thickness, create hooks that slide on perfectly and hold items. Teaches measurement precision and weight considerations.

3. Fitted Pencil Holder - Design a holder that fits a specific spot on your desk with compartments for different items. Teaches spatial planning and optimization.

4. Replacement Cap or Cover - Find something missing a lid (marker, container, etc.) and design a replacement that actually fits. Teaches reverse engineering and tight tolerances.

Success Criteria

You've completed this phase when you can:

• Measure an object and design something that fits it on the second try (first try is for experts!)
• Explain why you added 0.3mm gap instead of 0.5mm for a specific design choice
• Print a small test piece first without being reminded
• Keep a simple design log: what you changed between versions and why
• Solve an actual household problem with a custom-fitted print

Tips & Tricks

Test pieces are magic: Instead of printing a whole cable clip (1 hour), print just the clipping part (10 minutes). Test fit. Adjust. Save huge amounts of time.

The tolerance sweet spot: For parts that slide together, add 0.2-0.3mm. For snap-fits, try 0.4-0.5mm. Too tight? Sand it. Too loose? Print thicker.

Measure twice, design once: Take multiple measurements of the same dimension. If your ruler says "somewhere between 19 and 20mm," measure again more carefully.

Orientation for strength: Parts are strongest in the direction of layer lines. A hook printed flat will snap easier than one printed standing up.

Start with generous fits: New to tolerances? Make the gap bigger first (0.5mm). It's easier to tighten a design than loosen it after printing.

Real-world testing beats eyeballing: Don't just look at your CAD model and say "yeah, that'll fit." Print it. Test it. Learn from reality.

Easter Egg 🥚

Secret challenge: Design a two-piece puzzle where one part slides into the other with satisfying resistance—not too loose, not too tight. Get that tolerance perfect and you'll understand manufacturing better than most adults.

Pro tip: Every time you nail a fit on the second try instead of the fifth, that's your skills leveling up. Track your progress!