The Junior Tri-Gauge VM Lever Type Pit Gauge is today's most accurate Lever Pit Gauge, with a continuing tradition of Metric and dual Imperial Scales. The Junior Tri-Gauge serves its traditional use as a Pit Depth Gauge, but also as a Weld Inspection Gauge for: Weld Undercut Depth, Weld Crown Height, and both Metric and Imperial Rules. The Junior Tri-Gauge, like the original Tri-Gauge, is fitted with our Contact Point Offset Correction for improved accuracy and repeatability. Any Lever Pit Gauge is intended to evaluate corrosion / erosion, and not an absolute measuring tool. The Junior Tri-Gauge is supplied with a Vinyl Sheath Storage Case and Instructions.
Reading the Scale
The operator simply lines up the appropriate Pointer with the desired Scale; fractions of an inch (1/64"), millimeters (0.2mm), or thousands of an inch (0.005"). The scale is typically dictated by the reference Specification the inspector is employing, Corporate Guidelines, or the Jurisdiction that normally governs the selection of the scales to use.
Measuring Corrosion (Depth)
Extend the Lever to the maximum depth, so the Scale is also reading a maximum measure. Place the Contact Point into the Pit (or area of corrosion), and gently bring the Scale Plate Base of the Tri-Gauge firmly against the surface of the workpiece. The Scale Window will come to rest at the appropriate depth measurement.
The Contact Point of the Junior Tri-Gauge is specially formed to bring it in-line with the Contact Surface of the Scale Plate. This Offset Correction, ensures error is reduced if the Tri-Gauge is not normal (at right angles) to the surface of the workpiece.
Measuring Weld Reinforcement (Height)
Place the Lever to a neutral depth, so the Scale is also reading Zero. Place the Contact Point onto the top of the Weld Reinforcement, and gently bring the Scale Plate Base, of the Junior Tri-Gauge, firmly against the surface of the workpiece. The Scale Window will come to rest at the appropriate depth measurement.
Measuring Weld Undecut (Depth)
Weld Undercut measurement is identical to Pit Depth Measurement by simply extending the Lever to the maximum depth, so the Scale is also reading a maximum measure. Place the Contact Point into the Undercut, and gently bring the Scale Plate Base of the JuniorTri-Gauge firmly against the surface of the workpiece. The Scale Window will come to rest at the appropriate depth measurement.
It is important for the Operator to know if the Junior Tri-Gauge's Lever Arm and Contact Point are zeroed to the Scale. When the Contact Point is in contact with a flat surface, the Scale should read zero. However if there is an offset (positive or negative), the operator must be mindful to add or subtract the appropriate amount of error, thus keeping the measurement accurate.
Zeroing the Contact Point
When the Junior Tri-Gauge is manufactured a Skilled Technician Zeroed the Contact Point after the Offset Correction was induced into the Lever Arm. The Contact Point can become worn, damaged, or the Offset Correction can be damaged. Any Zero Offset can become a hindrance to the operator, so it may be desirable to Zero the Contact Point.
This Standardization can be performed by Western Instruments or you can attempt it yourself. If you attempt it yourself, you will need a small Ball Peen Hammer, an Anvil (or heavy plate), a Flat Plate, and a fine 6" file. You will need to determine if the Contact Point is too long or is too short. If the Contact Point is too short, it is placed on the Anvil, and the Hammer is used to Stretch the end by lightly taping the Contact Point. After each tap the Junior Tri-Gauge should be checked against the Flat Plate. If the Contact Point is too long, or you have stretched it too much, the Tip is lightly filed from the beveled or inner side (adjacent to the Scale Plate).