What It’s Called
- Name: Feeler gauge (also called a blade feeler gauge or thickness gauge)
- Type: A folding set of hardened steel blades, each blade stamped with a specific thickness (often in thousandths of an inch or millimeters).
- What your photos show: A fan-fold feeler gauge set with individual blades marked by thickness values; the handle stamp indicates “MOORE & WRIGHT” and “SHEFFIELD ENGLAND.”
When It First Appeared
- Core idea (measuring tiny gaps): Emerged alongside precision machining in the late 1800s, when industry needed repeatable ways to verify small clearances.
- Widespread everyday use: Became common in the early 1900s, especially as internal combustion engines spread and routine service required accurate clearance settings.
- “Vintage” workshop sets like this: Frequently associated with mid-20th-century mechanical service work (automotive, motorcycle, and general machine maintenance), though the same style remains in use today.
Who Created It
- Not a single inventor: The feeler gauge is best understood as a workshop-developed measuring tool refined by machinists, engineers, and toolmakers as tolerances tightened in manufacturing.
- Who made your example: The markings indicate manufacture by Moore & Wright, a well-known Sheffield, England toolmaker recognized for precision measuring tools.
What It’s Used For
A feeler gauge measures or sets a clearance (gap) between two parts where precision matters.
Most common mechanical uses (especially engines)
- Setting ignition points gap (classic distributor systems)
- Adjusting valve clearance / valve lash (rocker arms, tappets)
- Checking or selecting valve shims (when matching shim thickness to spec)
- Verifying spark plug electrode gap (some gauges are dedicated; feeler blades can assist depending on access and design)
General workshop uses
- Checking bearing, bushing, or sliding-fit clearances
- Confirming machine setup gaps (fixtures, guides, stops)
- Spot-checking alignment-related gaps on assemblies where a small clearance is specified
How It Works (Simple Explanation)
- Each blade is a known thickness.
- You insert a blade between two parts until it slides with a slight, even drag.
- The stamped value on the blade tells you the gap, or helps you set the gap by adjusting until the correct blade fits properly.
Key Features You Can Point Out in a “Vintage” Set
- Hardened steel blades for durability and consistent thickness
- Stamped thickness numbers on each blade (quick identification even when dirty)
- Pivot screw and folding handle for compact storage and quick selection
- Patina and surface staining that often indicates real shop use—common on older mechanic tools
Why This Tool Mattered Historically
- As engines and machines evolved, performance and reliability increasingly depended on tight tolerances.
- A simple tool like the feeler gauge made it practical for everyday mechanics to set critical clearances accurately, enabling:
- Smoother running engines
- Easier starting
- Reduced wear
- More consistent tune-ups without specialized measuring equipment
