There are three types of welding gauges that test different dimensions: flatness, thickness, and root opening.
Flatness gauges are used to measure the degree of curvature in a weld. The gauge has two V-shaped notches of different depths. The depth of the notch is measured with a micrometer before and after the weld is made. If the difference in depth is greater than the tolerance specified by the manufacturer, then the weld is considered to be out-of-flat.
Thickness gauges are used to measure the thickness of a weld bead. There are two types of thickness gauges: those that measure in millimeters (mm) and those that measure in inches (in). The former are more common in Europe while the latter are more common in America. To use a millimeter-based gauge, simply place it on top of the weld bead and read off the measurement indicated by the pointer. To use an inch-based gauge, first convert your measurement to inches using a conversion chart provided by the manufacturer or found online. Place the inch-based gauge on top of the weld bead and read offthe measurement indicated bythe pointer.
Root opening gauges are used to measurethe sizeof themelt pool created duringwelding .The mostcommon typeiscalledanEgger . It consists of asliding scale with numbered markings from 0to 10and two arms that can be positioned at any point alongthe scale .To usethe Egger , first make surethat both armsarepositioned at 0 . Next ,placeitunderneaththemeltpool so that one armis touchingthe bottomofthe pool whilethe otherarmrestson topofthe pool . Finally , slide themarkingscaley until both arms line upwith thenumber10 markingon opposite sidesofthe scale . Read offthe numberindicatedbythescale pointer;this will bethemaximumdepthofyourmeltpool .