Which tool is used to measure valve stretch?

Which tool is used to measure valve stretch?

• A. Micrometer
• B. Feeler gauge
• C. Contour or radius gauge
• D. Dial indicator

Answer: (C)

Measuring a curved surface, not just a single straight dimension, is what’s being tested here. A contour or radius gauge is built to check the shape of curved surfaces by matching various radii to the actual surface. Valve stems and related areas often have specific radii that must be preserved for proper seating and guide fit, so you’re checking whether the stem’s curvature matches the required profile. If the stem has stretched or distorted, the radius will no longer align with the template, which the gauge will reveal. In contrast, a micrometer measures a single linear diameter at one point, which doesn’t capture curvature. A feeler gauge checks clearances with flat or nearly flat gaps, not the surface’s curvature. A dial indicator assesses straightness or runout along an axis, not the actual radius of a curved surface. That’s why the contour or radius gauge is the best choice for detecting valve stem radius changes or “stretch” in a curved surface.

Measuring a curved surface, not just a single straight dimension, is what’s being tested here. A contour or radius gauge is built to check the shape of curved surfaces by matching various radii to the actual surface. Valve stems and related areas often have specific radii that must be preserved for proper seating and guide fit, so you’re checking whether the stem’s curvature matches the required profile. If the stem has stretched or distorted, the radius will no longer align with the template, which the gauge will reveal.

In contrast, a micrometer measures a single linear diameter at one point, which doesn’t capture curvature. A feeler gauge checks clearances with flat or nearly flat gaps, not the surface’s curvature. A dial indicator assesses straightness or runout along an axis, not the actual radius of a curved surface. That’s why the contour or radius gauge is the best choice for detecting valve stem radius changes or “stretch” in a curved surface.