# How to inspect an existing object using a radius gauge

### Step 1 – Select radius gauge set

Select a radius gauge set, either with single function blades or multi-function blades. Both gauges are capable of measuring concave and convex radii.

### Step 2 – Decide radius type

Decide whether you are measuring a concave or convex radius. For external measurements, a convex object requires a concave blade. Whereas a concave object requires a convex blade, (the reverse is true for internal radius measurements).

### Step 3 – Select blade

Separate a single blade and extend it from the case. Select a blade which has a curve close to the approximate size of the radius you wish to measure.

### Step 4 – Light object

Set up a bright light source behind the curved object being measured. This is so the clearance between the gauge and the surface being measured is clearly visible.

### Step 5 – Light object (contd)

Hold the object you wish to measure in between a source of light and your eye. This is an observational measurement because of the visual testing method.

Check to see if light is visible through between the object you are measuring and the gauge. If there is any light leakage, then the object’s radius does not match the radius of the selected blade.

### Step 7 – Match blade to object surface

Try to match the blade of the radius gauge to the object’s surface using trial and error. Once the gauge fits against an object’s surface, then you know the radius of the object is the same as the selected blade.

### Step 8 – If necessary, adjust surface

An object’s surface may not be able to match any of the blades because of an irregular curvature. In this case, the object may require adjustment to the radius. This can be done by re-cutting, grinding, sanding or buffing the surface.

### Step 9 – Measure object radius

After adjustment again try to fit blades against the surface. When surfaces fit together with no gap then you can read off the inscribed measurement to identify the object’s radius.