How do I measure blind rivet length and grip range?

Selecting the wrong size blind rivet (pop rivet) is one of the most common causes of joint failure, structural looseness, and broken setting mandrels. To achieve a strong, reliable joint, engineers and shop technicians must accurately determine two key dimensions: Grip Range and Rivet Body Length.

This technical guide walks you through the exact measurement formulas, step-by-step procedures, and sizing rules to ensure optimal fastening for your assembly line.

1. Key Definitions: Grip Range vs. Rivet Body Length

Before grabbing a caliper, it is important to understand the fundamental difference between these two parameters:

• Total Material Thickness (Grip Requirement): The combined thickness of all the sheets or components being joined together ($T_1 + T_2 + \dots$).

• Grip Range: The manufacturer-specified thickness range (minimum to maximum) that a specific rivet can securely clamp (e.g., $0.126″ – 0.250″$).

• Rivet Body Length ($L$): The physical measurement of the rivet shank, measured from underneath the head to the very end of the rivet tail (for standard dome heads).

2. Step-by-Step: How to Measure Combined Material Grip

To find the correct rivet, start by measuring the exact thickness of your assembly materials.

1. Clamp Materials Together: Ensure all metal plates or structural pieces are tightly clamped in their final installed position to eliminate gaps.

2. Measure Total Thickness: Use a digital vernier caliper or a depth micrometer through the pre-drilled rivet hole to measure the total combined thickness ($T$).

3. Select a Matching Grip Range: Choose a rivet whose Grip Range spans your measured thickness.

   • Example: If your total combined sheet thickness is 0.180″, select a rivet with a Grip Range of 0.126″ – 0.250″ (e.g., a standard -44 trade size rivet).

Pro Tip for Variable Thicknesses: If your production line deals with varying sheet metal thicknesses, consider Multi-Grip Blind Rivets. A single Multi-Grip SKU features an extended grip range (e.g., $0.078″ – 0.472″$), replacing up to three standard rivet sizes and reducing inventory management costs.

3. How to Measure Physical Rivet Length ($L$)

When measuring an existing rivet or verifying specs against a Technical Data Sheet, follow these head-style measurement rules:

A. Dome Head (Standard) & Large Flange Rivets

• Measure from the underside of the head (where the head sits flat against the work surface) to the end of the rivet body tail.

• Do NOT measure the mandrel/stem protruding from the back or top.

B. 120° Countersunk (Flush) Rivets

• Measure the entire length of the rivet, including the top of the countersunk head to the tip of the body tail.

• Because countersunk heads sit flush inside a chamfered hole, the head thickness is included in the total length calculation.

4. Standard Trade Numbering System (Decoded)

In North America, blind rivets use a standard 2-digit trade numbering system (e.g., Rivet #42, #64, #86) representing diameter and grip length in 64ths and 16ths of an inch:

Quick Trade Size Reference Chart

5. Consequences of Incorrect Sizing

• Rivet Too Short (Grip Range Exceeded): The mandrel head will snap before creating a full bulb on the blind side, causing joint separation under minimal shear load.

• Rivet Too Long: The body extends too far past the blind side, resulting in incomplete clamping force, loose assemblies, and potential internal rattling.

High-Quality Industrial Fasteners Stocked in the USA

Accurate sizing requires consistent manufacturing tolerances. At ProRivet, all our Open End, Closed End, and Multi-Grip blind rivets are built to rigid IFI and ISO engineering standards.

We stock complete size catalog ranges in Aluminum, Carbon Steel, and 304/316 Stainless Steel at our primary warehouse in Wheeling, Illinois (60090) for fast 1–3 day shipping across North America.

• Browse Sizing Catalog: Visit prorivet.com to inspect dimensional spec sheets.

• Get Engineering Support: Send your material stack-up specs to info@vortexdiamond.com  for professional rivet sizing recommendations.