You can create a gauge using column-type gauge. There are some specific configuration options that you can provide using the chart-gauge directive.

<c3chart bindto-id="gauge-plot1-chart">
    <chart-column column-id="Data 1"
                  column-values="70"
                  column-type="gauge"/>
    <chart-gauge min="50"
                 max="75"
                 units=" hours"
                 width="39"
                 show-label="true"
                 expand="true"
    />
</c3chart>