DISCOVER

# How to measure aviation rivets

Updated April 17, 2017

Rivets secure aircraft structures and parts all over an aeroplane. They are one of the most important and fasteners and are used on installations that need to be secure and permanent. But they will only work correctly when properly installed. Part of proper installation is selecting the right-sized rivets. Rivets that are too large will not form correctly and may damage the rivet holes, while rivets that are too small will not hold structures sufficiently.

Read the rivet's part number if it is available. The part number will tell you the rivet's exact length and diameter if you know how to read it. Every letter and number on an aircraft rivet is important but the last two numbers indicate the rivet diameter and length. So on a rivet with the part number MS20470 AD 4-7, 4 tells the diameter and 32ths of an inch and 7 tells the length in 16th of an inch. So the rivet is 4/32 of an inch wide (1/8th of an inch) and 7/16ths of an inch long.

Measure the length of a solid rivet manually from the top of the head to the end of the shank for flush mount rivets. Remember that length of aircraft rivets is indicated in 16ths of an inch, so don't measure with a metric ruler.

Measure the length of a solid rivet manually from the underside of the head to the end of the shank for universal rivets (rivets with a button shaped head). Still keep in mind that length of aircraft rivets is indicated in 16ths of an inch.

Measure the width of all solid rivets in 32nds of an inch. The rivet width should be slightly smaller than the width of the hole because the rivet will expand when installed.

Read blind rivet part numbers in the same way as solid rivets, remembering that the last two numbers represent width and length. But on a blind rivet, the last number does not indicate total length. It indicates grip length, which is equal to the total thickness of material that can be fastened with the rivet.

Measure the total length of a blind rivet manually from the top of the head to the end of the shank for flush mount rivets. Also measure this length in 16ths of an inch. But the overall length is less important with a blind rivet because its part number will tell you exactly what thickness of material it can be used with.

Measure the total length of a blind rivet manually from the underside of the head to the end of the shank for universal rivets (rivets with a button shaped head)Still keep in mind that length of aircraft rivets is indicated in 16ths of an inch. Again, it is easier to get the grip measurement from the blind rivet's part number.

Measure the width of all blind rivets in 32nds of an inch. The rivet width should be slightly smaller than the width of the hole because the rivet will expand when installed.

#### Tip

A solid rivet's total length is greater than its grip length, so you can't drive a rivet that is 4/32s of an inch through 4/32 of an inch of metal. The rivet must be longer than the material thickness. The exact dimensions needed differ according to the rivets length and diameter, so check you maintenance or installation documentation or FAA advisories if needed.

• Rivets
• Small ruler