The original uploader was Graibeard at English Wikipedia., CC BY-SA 2.0, via Wikimedia Commons
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The thing in the image above might look like a Swiss Army knife, but it isn’t. It’s a “feeler gauge.” In this Tool Tutorial, you’ll learn:
- What a feeler gauge is
- Its common uses
- How to use one to measure a spark plug gap
What is a “Feeler Gauge?”
A feeler gauge is a tool used to measure the gap between two spaces closed together where a regular tape measure won’t fit. The tool contains a series of small blades inside a metal container that can be bought individually or as a kit. However, these blades aren’t for cutting – they’re for measuring. Each blade has a stamp of its thickness on the side. For example, this blade has a thickness of 0.40 mm (or approximately 0,02 inches):
Uses of a Feeler Gauge
In the context of motorcycle mechanics, some common uses include:
- Measuring spark plug gaps
- Measuring valve play in an overhead camshaft engine
How to use a feeler gauge – step-by-step
- Bring out the object whose gap you want to measure (in my case, I’ll use a spark plug)
2. Fold out one of the blades and stick it into the gap you want to measure:
The blade is supposed to go into the slot with little to no wiggle room. If you’ve got too much wiggle room, you need to choose a thicker blade. If you can’t get the blade through the gap, you need a thinner blade.
Once you’ve found one that is thick enough to fit in the slot but small enough so that they’re very little wiggle room, you’ve found the correct measurement. Look at the specs on the side of the blade and note the measurement. In the image above, the blade had a with of 0.50mm – therefore, the spark plug gap is 0.50mm wide.