Measuring a socket primarily involves identifying its size, which indicates the dimension of the fastener head it is designed to fit.
Socket sizes are based on standard measurement systems used worldwide. According to the reference provided, socket sizes are divided into two main systems:
- SAE (Society of Automotive Engineers): This system is also known as imperial and is measured in inches.
- Metric: This system is measured in millimeters.
Both popular socket types, 6-point and 12-point sockets, are measured using these two systems.
Understanding Socket Measurement Systems
The size marked on a socket refers to the inner diameter of the opening that fits onto the bolt or nut head. This measurement is crucial for selecting the correct socket for a task.
Here’s a quick look at the systems:
| System | Units | Examples | Common Range (Metric from Reference) |
|---|---|---|---|
| SAE | Inches (in.) | 1/4", 3/8", 1/2", 7/16" | Not specified in reference |
| Metric | Millimeters (mm) | 10mm, 13mm, 19mm, 22mm | 5.5mm to 24mm |
The reference highlights that a popular range for metric sockets is 5.5mm to 24mm. SAE sizes commonly include fractions like 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", etc.
How to Physically Measure a Socket
While most sockets have their size clearly marked on the side, the marking can wear off over time. If the size isn't visible, you can measure the socket using a tool:
- Use a Caliper: The most accurate way is to use a caliper (either digital or dial). Measure the distance between the parallel flat sides of the hexagonal or square opening where the bolt head fits.
- Use a Socket Gauge: Some specialized tools or sorting trays have cutouts of various standard sizes. You can test-fit the socket onto these gauges to find the one it matches perfectly.
Practical Tip: When measuring with a caliper, ensure you are measuring across the flats of the opening, not across the points.
Socket Types and Measurement
As mentioned, both 6-point and 12-point sockets are measured in the same way – by the size of their opening that fits the fastener. The number of points (or facets) inside the socket relates to how many contact points it has with the bolt head, affecting grip and clearance, but not the size measurement itself.
- 6-point sockets: Grip the six sides of a hex bolt head, offering good grip and reducing rounding, especially on stubborn fasteners.
- 12-point sockets: Can fit onto a hex bolt head in more positions (12 vs 6), making them easier to position in tight spaces.
Both types rely on the accurate measurement of the distance across the flats of the fastener head (or socket opening), measured in either inches (SAE) or millimeters (Metric).
