Nut and Bolt Size Gauge: A Quick Guide to Measuring Bolts and Nuts

What the Champion Nut and Bolt Size Gauge Can Measure:

  • UNC and UNF thread sizes.
  • Metric and Imperial bolt/set screw sizes.
  • Conversion between Metric and Imperial tensile strength (from SAE to ISO).

Tip: The easiest way to determine if a bolt/set screw is Metric is by examining the top of the head (This is also where you’ll find the manufacture’s marking e.g W.T). Markings such as 5.8, 8.8, 9.8, 10.9, or 12.9 indicate a Metric bolt. Any other type of marking suggests it’s Imperial. You can discover more about Metric and Imperial bolts here.

Using the Gauge:

  1. Match the Nuts: Align the nuts with the correctly fitting peg on your gauge, labelled either “UNC” or “UNF”. UNC should fit snugly, while UNF may have a slight wiggle.
  2. Find the Match: Once the bolt slots perfectly onto the peg, you’ve identified your size. The label next to the peg (see example below, “1/2 UNC”) will indicate this size.

Bolt Length:

  • To measure the bolt’s length, align it along the gauge’s ruler edge, as indicated. The gauge provides multiple measuring points along the thread gauge to accommodate various bolt head types, ensuring an accurate measurement.

Measuring Thread Sizes with the Champion Gauge

  1. Start with Inspection and Identification: Begin by visually inspecting the bolt or set screw. Look at the markings on the top of the head; Metric bolts often have markings such as 5.8, 8.8, 9.8, 10.9, or 12.9, indicating their grade. In contrast, Imperial bolts may have different or no clear grade markings. This preliminary check can help you estimate not only the likely size range but also whether you’re dealing with a Metric or Imperial thread, making the measuring process smoother.
  2. Insertion Test: Insert the bolt or set screw into the holes on the gauge. Start with the hole size you believe is the closest match. The right hole is the one that the bolt or set screw fits into best without too much wiggle room or resistance.
  3. Read the Label: Each hole on the Champion Gauge is clearly labelled with the thread size. Once you’ve found the correct fit, note the size indicated by the gauge. This measurement is crucial for matching the bolt or set screw with the correct nut or threaded hole in your project.

Nut and Bolt Size Gauge

UNC & UNF Thread Measurement:
Designed to accurately measure both UNC (Unified Coarse) and UNF (Unified Fine) thread sizes.
Length and Diameter Measurement:
It’s suitable for measuring the length and
diameter of UNC, UNF, Metric, and SAE.
Quick Size Identification:
Enables fast and easy determination of the exact length, width, and diameter of nuts and bolts.
Precision Measuring Tool:
Constructed from ABS plastic for accurate measuring. It also includes SAE to ISO
hardness conversion.

Read more here

Part No: CSG-1 Category:

Additional information

Product Category

Tools & Ancillaries

Quick Connectors and Covers.