Are spark plugs metric or imperial?
Spark plugs are gauged by their thread diameter, the common ones being 18, 14, 12, 10 and 8mm. The threads are metric fine. To confound things, old UK plugs are imperial, as are USA varieties. The hexagon to undo them is also metric (with the above exclusions) and the size can vary with the manufacturer.
What metric size is a spark plug?
Metric threads spark plugs according ISO 28741
| Size | Major Diameter (mm) | Pitch (mm) |
|---|---|---|
| M10 x 1.0 | 10.0 | 1.00 |
| M12 x 1.25 | 12.0 | 1.25 |
| M14 x 1.25 | 14.0 | 1.25 |
| M18 x 1.5 | 18.0 | 1.50 |
How are the threads of a spark plug measured?
A spark plugs threads are comprised of 3 dimensions: Reach, Diameter and Pitch. Thread pitch is the distance between threads expressed in millimetres. For example, a thread pitch of 1.25 means the distance between each thread is 1.25mm.
Is there difference between metric and nominal spark plug threads?
No, Mike72, your take on spark plug threads is not correct. The tolerance from nominal size is different on a spark plug than a standard metric thread. I don’t remember whether it is larger or smaller, but it is not the same. For a backyarder it may not matter, but don’t complain if your sparkplug strips or seizes.
How many threads are in a SAE spark plug?
According to Machinery’s Handbook (24th ed pg 1650), there are four standard SAE spark plug threads, all metric: M18 x 1.5; M14 x 1.25; M12 x 1.25; and M10 x 1.0
What are the ISO 28741 spark plug threads?
Spark plug threads according ISO 28741 Road vehicles — Spark-plugs and their cylinder head housings — Basic characteristics and dimensions. 1) Tolerance class 6H. Sorry to see that you are blocking ads on The Engineering ToolBox! If you find this website valuable and appreciate it is open and free for everybody – please contribute by
A spark plugs threads are comprised of 3 dimensions: Reach, Diameter and Pitch. Thread pitch is the distance between threads expressed in millimetres. For example, a thread pitch of 1.25 means the distance between each thread is 1.25mm.
Spark plug threads according ISO 28741 Road vehicles — Spark-plugs and their cylinder head housings — Basic characteristics and dimensions. 1) Tolerance class 6H. Sorry to see that you are blocking ads on The Engineering ToolBox! If you find this website valuable and appreciate it is open and free for everybody – please contribute by
What happens when a spark plug is over torqued?
An under-torqued spark plug can lead to excessive vibration and improper heat dissipation, causing spark plug and/or engine damage. An over-torqued spark plug may cause thread damage or breakage, or compromise internal seals within the spark plug, leading to improper heat dissipation or exhaust gas blow-by.
What makes the NGK spark plugs so durable?
NGK spark plugs feature trivalent plating. This silver or chrome-colored finish on the threads is designed to provide corrosion resistance against moisture and chemicals. The coating also acts as a release agent during spark plug removal. NGK spark plugs are installed at the factory dry, without lubrication or anti-seize.