Small Differences.
Big Impact.
Is your bore really the right size? Discover how Mitutoyo bore gauges and inside micrometers help you measure internal diameters with confidence.
Looks Round. But Is It Accurate?
A cylinder bore can look perfectly fine but still be slightly oversized, tapered, or uneven. In precision work, those small differences matter.
Whether you're rebuilding an engine, machining a component, or inspecting a bearing housing, the right measuring instrument helps you make informed decisions before assembly.
Not sure where to start? Let's find the tool that matches your job.
What Are You Measuring Today?
Choose your application below. Tap an option to discover which Mitutoyo instrument is worth considering.
🔧 I'm checking an engine cylinder bore.
Dial Bore Gauge
Useful for comparing cylinder diameters at different depths and directions, helping you investigate taper and out-of-round conditions.
Check first: Bore diameter, measurement depth, and required tolerance.
Explore Bore Gauges⚙️ I'm inspecting a small precision hole.
Extra-Small Bore Gauge or Small-Hole Gauge
Series 526 is designed for extra-small internal measurement. Series 154 transfers a small-hole dimension to a suitable outside micrometer.
Check first: Hole diameter, tolerance, and access.
Explore Small Bore Tools📏 I need a direct internal measurement.
Inside Micrometer
Provides a direct measurement of an internal dimension when properly positioned and verified.
Check first: Required internal span and instrument range.
Explore Micrometers🧰 I measure several different internal sizes.
Interchangeable-Rod Inside Micrometer
Uses compatible interchangeable rods to cover multiple internal measuring ranges.
Check first: Included rods, overall range, and setup requirements.
Explore MicrometersOne Bore. Four Things to Check.
Internal diameter inspection is about more than getting one number.
Diameter
Is the bore within the required dimensional tolerance?
Taper
Does the measured diameter change along the bore?
Out-of-Round
Do diameter measurements differ between orientations?
Component Fit
Will the measured dimension support the intended fit?
Curious About Measuring Terms?
What's comparative measurement?
Comparative measurement checks how far a dimension differs from a known reference. A dial bore gauge is typically set to a reference before measuring the workpiece.
What's direct measurement?
A direct-reading instrument provides a dimension on its own scale or display. Inside micrometers are an example, although correct technique and verification remain essential.
Does 0.01 mm resolution mean 0.01 mm accuracy?
No. Resolution describes the smallest displayed increment. Overall accuracy also depends on the instrument specification, reference, calibration, conditions, and technique.
Meet the Tools Behind the Measurement.
Explore these Mitutoyo product families and models referenced in KHM Megatools' listings.
511-711-20 Bore Gauge
Listed range: 18–35 mm
For comparative measurement of smaller internal diameters.
Explore Collection →511-712-20 Bore Gauge
Range: Confirm before ordering.
For internal diameter comparison. KHM's product listing contains a range discrepancy, so verify the exact manufacturer specification.
View Product →511-713-20 Bore Gauge
Listed range: 50–150 mm
Useful for larger bores, including suitable cylinder and housing inspection applications.
View Product →511-714-20 Bore Gauge
Listed range: 100–160 mm
For larger internal diameter inspection within its measuring range.
View Product →Extra-Small Bore Gauges
Designed for small internal openings where a larger conventional bore gauge may not fit.
Explore Collection →Inside Micrometers
Single-rod tubular instruments for direct internal dimension measurement.
Explore Collection →Interchangeable-Rod Micrometers
Suitable for multiple internal measuring ranges using compatible rods.
Explore Collection →154-902 Small-Hole Gauge Set
Listed range: 3–13 mm, four-piece set.
Transfers internal dimensions for measurement with an outside micrometer.
View Product →Which Tool Fits Your Workflow?
| Instrument | Method | Best Considered For |
|---|---|---|
| Series 511 Bore Gauge | Comparative | Cylinder bores and diameter variation |
| Series 526 Bore Gauge | Comparative | Extra-small holes |
| Series 133 Inside Micrometer | Direct | Internal spans within model range |
| Series 141 Inside Micrometer | Direct, interchangeable rods | Several internal measuring ranges |
| Series 154 Small-Hole Gauge | Transfer | Small holes with outside micrometer measurement |
From Zero to Measurement.
Here's a simplified workflow for using a dial bore gauge. Follow the instructions for your exact instrument.
Know Your Target
Identify the nominal diameter, tolerance, and inspection positions.
Choose the Correct Range
Use a gauge suited to the bore's diameter and required depth.
Set the Reference
Use an appropriate setting ring or approved reference arrangement.
Find the Reversal Point
Carefully position and rock the gauge through the measuring axis.
Compare and Record
Check the required depths and directions, then document the results.
Think You Know Your Measurements?
Try this quick exercise before revealing the answer.
What's the Bore Diameter?
Your gauge is set against a 50.000 mm reference. The bore is measured to be 0.020 mm larger.
Choose your answer:
A — 49.980 mm
Not quite. This result would mean the bore is smaller than the reference.
B — 50.020 mm
Correct! 50.000 + 0.020 = 50.020 mm.
C — 50.200 mm
Almost! Watch the decimal places. The difference is 0.020 mm, not 0.200 mm.
Simplified example. Actual dial interpretation depends on the instrument's reference setup and reading convention.
Ready to Measure? Check These First.
A quick checklist can help you avoid preventable measurement mistakes.
Still Have Questions?
Can a bore gauge detect cylinder taper?
Yes. Comparing readings at different depths helps identify diameter changes along the cylinder.
Can I use an inside micrometer instead of a bore gauge?
Both measure internal dimensions, but they use different methods. Choose based on whether direct measurement or comparative inspection better matches your task.
Which instrument should I use for a 75 mm bore?
A gauge covering 75 mm, such as the listed Series 511 model 511-713-20 with a 50–150 mm range, may be suitable. Confirm depth, tolerance, and accessories.
Do I need a setting ring?
A suitable reference is necessary for comparative measurement. Follow the manufacturer's approved setting methods.
Where can I buy Mitutoyo measuring tools in the Philippines?
Explore Mitutoyo measuring instruments at KHM Megatools and check individual listings for product details and availability.
Your Next Accurate Measurement Starts Here.
Explore Mitutoyo bore gauges and inside micrometers for your workshop, machining, and industrial inspection requirements.
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