Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
A feeler gauge is a set of thin metal leaves that measure gaps and clearances between engine parts, bearing surfaces, and adjustable components. Using it correctly means finding the leaf that fits with a light, consistent drag through the gap. Once you have the measurement, consult your equipment manual to find what the clearance should be for your specific model or application.
Necessary equipment
| Item | Note |
|---|---|
| Feeler gauge set | Spring steel leaves. Sizes from 0.002 inches to 0.250 inches thick, or 0.05 mm to 6.35 mm. |
| Flashlight or work light | Permits clear visibility of the gap and blade. |
| Clean cloth material | Lint-free cloth. Clean the gauge leaves with it. Clean the surfaces to measure with it. |
| Degreaser or solvent material | Removes oil, grease, and dirt from surfaces. |
Specifications
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Procedure
Estimated 18 min
- Examine each leaf for bends, rust, pits, or discoloration. Bend each leaf slightly. Release it. It must snap straight back. Discard any damaged leaf.1mReport a problem with step 1, Procedure
- Wipe the feeler gauge leaves with a lint-free cloth. Clean the gap and surrounding area with degreaser to remove oil, dirt, and debris. Dry all surfaces.3mReport a problem with step 2, Procedure
- Start with a leaf you think is close to the gap width. If it slides through freely, select the next thicker leaf. Continue until you find a leaf that enters the gap with resistance.2mReport a problem with step 3, Procedure
Do not force a leaf through a gap.
Excessive pressure bends the leaf, damages the gap, or produces incorrect measurement. Push with gentle, steady force only.
- Slide the leaf straight into the gap. Do not tilt or angle it. Keep the leaf parallel to the surfaces above and below the gap. If you angle the leaf, the measurement will be incorrect.2mReport a problem with step 4, Procedure
- Pull the leaf slowly through the gap. The leaf must produce a steady pull. Feel this resistance throughout the entire pull. The leaf must not drop through freely. The leaf must not require hard force.2mReport a problem with step 5, Procedure
- Try the next thicker leaf. It must not enter the gap, or it must enter only with excessive force. If the thinner leaf slides easily, your selection is correct. If the thicker leaf slides in, try the next size.2mReport a problem with step 6, Procedure
- Look at the stamped or engraved number on the leaf. The number indicates thickness in inches (example: 0.010 in) or millimetres (example: 0.25 mm). Record both the leaf size and the unit.1mReport a problem with step 7, Procedure
- Consult the service manual for the specific machine or engine. Find the specification section for that clearance type (example: spark plug gap, valve clearance, bearing clearance). Compare your measurement to the specification.5mReport a problem with step 8, Procedure
Inspection and storage
Estimated 2 min
A bent leaf will produce an incorrect measurement.
A pitted leaf will produce an incorrect measurement. Discard damaged leaves. Do not use a bent gauge for critical clearances.
- Before storage, inspect every leaf one more time. Remove any leaf with a permanent bend or flat spot. Replace it.1mReport a problem with step 1, Inspection and storage
- Fold the leaves back into the case. Do not leave leaves open. Open leaves can bend under their own weight or if bumped. Store in a clean, dry location.<1mReport a problem with step 2, Inspection and storage
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- Feeler gauge
- Also called: no common alternatives
- Leaf
- Also called: no common alternatives
- Clearance
- Also called: no common alternatives
- Drag
- Also called: no common alternatives
When to use a professional
If your measurement is outside the correct range, contact a qualified technician. If parts require adjustment or replacement, consult the service manual.
Common questions
What is the difference between a feeler gauge and other measuring tools?
A feeler gauge measures gaps by direct insertion into the space. It is faster than dial calipers or micrometers for gap measurement and works in tight or awkward spaces where other tools cannot fit. Feeler gauges are less precise (typically ±0.002 to ±0.004 inches) but practical for field adjustment work.
Why does the leaf have to be parallel to the gap?
If you tilt or angle the leaf, it wedges into the gap at an angle and reads thicker than it actually is. A parallel insertion gives an accurate measurement. Tilting is one of the most common sources of measurement error.
What does 'light drag' feel like?
Imagine pulling a sheet of thin paper between your thumb and finger with gentle, steady pressure. The paper slides through but you feel consistent resistance the whole way. That sensation is the light drag you want in a feeler gauge. Too easy means the leaf is too thin; too hard means it is too thick or you are tilting it.
Can I use a bent feeler gauge?
No. A bent leaf is scrap. Even a small bend changes the thickness and produces a false measurement. Bent leaves result from dropping the gauge, storing open leaves where they can sag under their own weight, or forcing a leaf into a gap at an angle.
Why do I need to consult the manual for the clearance figure?
Every engine and component is designed with a specific clearance range. Too much clearance can cause noise, vibration, or wear. Too little can cause binding or overheating. The manual gives you the correct figure for your exact model. The feeler gauge tells you what the clearance IS; the manual tells you what it SHOULD be.
How do I know which leaf to start with?
Start with a leaf you estimate is close to the gap size. If it slides through easily, try the next thicker leaf. Keep trying progressively thicker leaves until one enters with light drag. This method is called 'Go, No Go'—the leaf that goes through with controlled resistance is your measurement.
Related procedures
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Thickness or Feeler Gages
- Tier 1DIN 2275:2014 - Feeler gauges
- Tier 1Thickness Feeler Gages
- Tier 2A Complete Guide to Feeler Gauges
- Tier 2All About Feeler Gauges – Definition, Sizes, and Uses
Revision history
Current version 1 · updated 2026-08-03 · next review due 2027-08-03
- v · 2026-08-03Initial draft from tier-1 sources: Starrett, Mitutoyo, DIN 2275 standard, RS Online technical guide.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.