Creating Holes & Subtractive Design – Advanced Techniques

Introduction

Subtractive design—creating shapes by removing material—is one of TinkerCAD's most powerful features. This guide covers advanced hole creation, complex cutouts, and practical applications like cable organisers and modular storage systems.

Understanding the "Hole" Function

How Holes Work in TinkerCAD

Unlike traditional CAD software, TinkerCAD uses a simple but powerful approach:

1. Create an outer shape (the solid object)
2. Create an inner shape (the shape to remove)
3. Mark the inner shape as a "Hole"
4. When exported, the inner shape is subtracted from the outer shape

Key Principle

The hole shape must be completely inside the outer shape. If any part extends beyond the outer boundary, the subtraction won't work as expected.

Creating Your First Hole

Step-by-Step Example: A Simple Box with a Hole

1. Create Outer Box: Add a cube, set dimensions to 50mm × 50mm × 20mm
2. Create Inner Hole: Add another cube, set dimensions to 20mm × 20mm × 20mm
3. Position the Hole: Set position to X=15mm, Y=15mm, Z=0mm (centered horizontally, flush with bottom)
4. Mark as Hole: Select the inner cube, right-click, and choose "Make a Hole"
5. Verify: The inner cube should now appear transparent/ghosted, indicating it's a hole
6. Group Together: Select both shapes and press Ctrl+G to group them

Result: When exported, you'll have a solid box with a 20mm × 20mm square hole through it.

Practical Project: Cable Organizer

Let's design a functional cable organiser with multiple holes for different cable types.

Design Specifications

• Overall Dimensions: 80mm × 40mm × 30mm
• Material: PETG (durable for repeated use)
• Wall Thickness: 2.5mm
• Hole Diameters: 8mm (USB), 12mm (Power), 15mm (HDMI bundle)

Construction Steps

1. Create Main Body: Cube 80mm × 40mm × 30mm
2. Create Hollow Interior: Cube 75mm × 35mm × 25mm, positioned at X=2.5mm, Y=2.5mm, Z=2.5mm, marked as hole
3. Create USB Hole: Cylinder with 4mm radius, 30mm height, positioned at X=15mm, Y=20mm, Z=0mm, marked as hole
4. Create Power Hole: Cylinder with 6mm radius, 30mm height, positioned at X=40mm, Y=20mm, Z=0mm, marked as hole
5. Create HDMI Hole: Cylinder with 7.5mm radius, 30mm height, positioned at X=65mm, Y=20mm, Z=0mm, marked as hole
6. Group All: Select all shapes and group them together

Design Considerations

• Hole Depth: Make holes go completely through (height = body height)
• Hole Positioning: Center holes vertically (Y=20mm for 40mm-wide body)
• Spacing: Leave 10mm minimum between hole centers to maintain structural integrity
• Diameter Tolerance: For cables, add 1–2mm clearance to the actual cable diameter

Advanced Hole Techniques

Technique 1: Threaded Holes

For screw holes, create a cylindrical hole slightly smaller than the screw diameter:

• M3 Screw: Create a hole with 1.5mm radius (3mm diameter)
• M4 Screw: Create a hole with 2mm radius (4mm diameter)
• M5 Screw: Create a hole with 2.5mm radius (5mm diameter)

Pro Tip: The screw will slightly deform the plastic as it threads in, creating a secure fit.

Technique 2: Countersunk Holes

For flush screw heads, create a cone-shaped recess:

1. Create a cylindrical hole for the screw shaft (e.g., 1.5mm radius)
2. Create a cone above it (base radius 3mm, height 2mm) to recess the screw head
3. Mark both as holes
4. Result: A screw head sits flush with the surface

Technique 3: Slots and Rectangular Cutouts

For cable slots or rectangular openings:

1. Create a cube with dimensions matching your desired slot (e.g., 30mm × 5mm × 20mm)
2. Position it where you want the slot
3. Mark as hole
4. Result: A rectangular opening for cables or tabs

Complex Cutout Example: Modular Storage System

Design stackable storage boxes with interlocking tabs and slots.

Design Specifications

• Box Dimensions: 60mm × 40mm × 30mm
• Tab Height: 5mm
• Slot Width: 2.2mm (for 2mm wall thickness)
• Material: PLA (cost-effective for multiple units)

Construction

1. Create Main Box: Cube 60mm × 40mm × 30mm with hollow interior (2mm walls)
2. Create Side Tabs: Two cubes 5mm × 40mm × 5mm on opposite sides (for stacking)
3. Create Slot Cutouts: Four rectangular holes 2.2mm × 40mm × 5mm on adjacent sides (to receive tabs from other boxes)
4. Create Divider Slot: One rectangular hole 2.2mm × 40mm × 28mm in the center (for optional divider)
5. Group All: Select all and group

Assembly Logic

When printed:

• Tabs on one box slide into slots on adjacent boxes
• Boxes stack vertically and horizontally
• Optional dividers insert into the center slot
• System is modular and reconfigurable

Hole Positioning Precision

For accurate hole placement, use this formula:

• Horizontal Center: Body Width ÷ 2 = X Position
• Vertical Center: Body Depth ÷ 2 = Y Position
• Depth Position: 0 (for through holes) or specific Z value (for blind holes)

Example: Centering a Hole in an 80mm × 60mm Box

• X Position: 80 ÷ 2 = 40mm
• Y Position: 60 ÷ 2 = 30mm
• Z Position: 0 (for through hole)

Common Hole Design Mistakes

Mistake	Problem	Solution
Hole extends beyond outer shape	Subtraction fails; hole doesn't appear	Ensure hole is completely inside outer boundary
Hole too small for intended use	Cable won't fit; screw won't thread	Add 1–2mm clearance to actual dimensions
Multiple holes too close	Thin walls between holes; parts break	Maintain 3mm minimum wall between holes
Forgot to mark as hole	Inner shape prints as solid	Select inner shape and right-click "Make a Hole"
Hole positioned off-center	Aesthetically poor; functional issues	Use positioning formula to center precisely

Exporting Designs with Holes

When you export a design with holes:

1. TinkerCAD automatically performs the subtraction
2. The exported STL file contains the final geometry (no separate hole objects)
3. Your slicer software sees a single solid object with cutouts

Pro Tip: Before exporting, rotate your design and verify that holes appear correctly from all angles.

Key Takeaways

• Holes must be completely inside outer shapes
• Use cylinders for round holes, cubes for rectangular cutouts
• Add 1–2mm clearance for functional holes (cables, screws)
• Maintain 3mm minimum wall thickness between holes
• Use precise positioning formulas for centred holes
• Mark all hole shapes before grouping and exporting

Next in the series: Adding Text, Importing Models & Advanced Features