Thickness Gauges

There are several types of thickness gauges used in luthiery, each suited for specific measuring tasks.

Best for: Measuring the thickness of tops, backs, and sides during shaping.
How it works: Uses a dial indicator with a measuring probe that contacts the wood surface, providing a precise reading.
Advantages:
- No batteries required.
- Highly precise, typically measuring in increments of 0.01 mm (0.001 inches).
- Reliable in dusty workshop environments.
Uses in Luthiery:
- Ensuring consistent thickness in soundboards and backs.
- Measuring rib and side thickness before bending.
- Checking brace thickness before gluing.

Best for: Quick and highly accurate thickness measurements.
How it works: Similar to a dial gauge but features a digital display for easy reading.
Advantages:
- Provides instant digital readings.
- Can switch between metric and imperial units.
- Higher accuracy, often up to 0.01 mm (0.0005 inches).
Uses in Luthiery:
- Fine-tuning critical wood thicknesses.
- Checking plate graduation on archtop guitars and violins.
- Measuring veneers and purfling strips.

Best for: Measuring small, thin pieces such as veneers, bindings, and purfling.
How it works: Functions like a caliper but with a measuring probe for precise thickness reading.
Advantages:
- Compact and easy to use.
- Suitable for detailed component work.
- Ideal for checking nut and saddle thicknesses.
Uses in Luthiery:
- Measuring binding and purfling stock.
- Checking nut and saddle thickness before shaping.

Best for: Measuring thickness at the center of large plates like guitar tops and backs.
How it works: Features an extended frame to allow measurements deep into the material, ensuring uniform thickness across the entire surface.
Advantages:
- Allows measurement at various points across a large piece of wood.
- Essential for tuning the thickness of instrument tops and backs.
- Typically used with dial or digital indicators for high accuracy.
Uses in Luthiery:
- Ensuring soundboard and back graduation in acoustic instruments.
- Measuring the thickness of bent sides and braces.

Best for: Measuring small gaps and clearances in luthiery setups.
How it works: A set of thin, flat metal strips in varying thicknesses, used for checking tight tolerances.
Advantages:
- Very precise for measuring clearances in nuts, saddles, and truss rod adjustments.
- Affordable and easy to use.
Uses in Luthiery:
- Checking nut slot depth.
- Measuring truss rod relief.
- Ensuring proper glue joint clearances.

Applications of Thickness Gauges in Luthiery

The thickness of a guitar or violin’s soundboard greatly influences its tonal response.
A deep-throat thickness gauge ensures consistency across the entire surface, helping maintain even graduation.
Different thicknesses are required for different woods and playing styles:
- Spruce top (acoustic guitar): Typically 2.2 mm – 3.0 mm.
- Backs (rosewood, mahogany, maple): Typically 2.5 mm – 3.5 mm.
- Sides: Typically 1.5 mm – 2.5 mm.

Braces must be carefully tapered and graduated to balance strength and resonance.
Dial or digital thickness gauges help ensure precise dimensions before gluing.

Bent sides must maintain a uniform thickness to avoid weak spots.
A dial or digital thickness gauge helps monitor thickness before final shaping.

Nut and saddle thickness must match the slots precisely for optimal tone transfer.
A caliper-style thickness gauge or feeler gauge ensures an exact fit.

Thin decorative elements require precise measurements to ensure proper seating in routed channels.
Caliper-style thickness gauges are ideal for measuring these materials.

When selecting a thickness gauge, consider the following factors:

Measurement Accuracy: Look for gauges that measure down to at least 0.01 mm (0.001 inches).
Depth Capability: For large plates, choose a deep-throat gauge to measure at various points.
Ease of Reading: Digital gauges are easier to read, while dial gauges work well in dust-prone workshops.
Durability: Stainless steel components last longer and maintain accuracy.

Keep gauges clean: Dust and wood particles can affect accuracy.
Store properly: Keep gauges in protective cases to avoid damage.
Calibrate periodically: Check against known thicknesses to ensure accuracy.
Handle gently: Avoid dropping gauges, as this can misalign the measuring mechanism.