Tooke Paint Inspection Gauges
Measures Thickness of Coatings Applied to Wood, Plastic, Cement, Glass, Ceramics, Mirror Backings, Metal, Etc.
Assists in Measuring Brittleness and Adhesion of Coatings and Materials.
Model OG202 & OG204 are supplied with 1X, 2X, & 10X cutting tips installed in the gage body. The 2X tip is shown extended to working position.
Direct measurement of total coating thickness, and thickness of individual coats of paint is a unique capability of the “Tooke Gauge.” Thus, in addition to routine use, it often serves as a “referee” instrument to calibrate indirect or “non-destructive” thickness measuring instruments. Other uses include assessment of substrate conditions and coating adhesion, and observation of microscopic cracking, tendency for brittleness, blistering, cratering, or other microscopic film symptoms.
The OG202 gauge body, cap, and focusing ring, are machined aluminum. The OG204 gauge body is made of injection molded high-impact plastic. It contains the microscope and lamp batteries as well as the groove-cutting tungsten carbide cutting tools mounted on the narrow side. In addition to the cutting tools, two adjustable threaded guide studs also project from the body on the same side.
The tripod thus formed by the three legs (guide studs and tool) provides for precise alignment of the tool with a surface to be grooved. A lanyard and keeper looped through the body secure the instrument to the inspector’s wrist. A flexible carrying case with neck strap is compartmentalized to include: the gauge, a felt-tipped marker, and extra batteries and bulb. The entire unit is designed for convenience and completeness in field inspection tasks.
Both gages now come with LED bulbs which are much more rugged than the incandescent bulbs and are expected to last some 50,000 hours. The LED bulbs are also available for purchase as replacements. (Incandescent bulbs are also still available.)
Open the carrying case and remove the instrument. For field use, secure the safety lanyard to the
wrist to prevent accidental dropping. Check the positioning of the cutting tips. As originally supplied, the tip positions will be from top to bottom 1X, 2X, and 1oX. The numerals 1, 2, and 10 are engraved in the body alongside each tip respectively. The 1X and 1oX tips will be bottomed in their slot, thus protruding about 3/16" from the case. The 2X tip (center position) should be in working position, thus protruding about 5/16" from the case. In general, this is the correct configuration for making an initial measurement on a film.
Make a small mark with the brush-pen at the desired measurement location on a painted surface. Grasp the instrument with the cutting tip down as shown in Fig. 2. Place the cutter tip and guide studs in firm contact with the surface with the tip slightly above the mark and aligned to scribe across the mark. Align the forearm with the intended cutting direction to assure a straight cut. Draw the cutter tip straight across the mark, applying just sufficient pressure at the tip to cleanly penetrate through the film into the substrate. In this operation, the cutter trails midway between the two guide studs, and continuous 3-point surface contact should be maintained to assure precise vertical alignment of the groove. Excessive pressure on the guide studs should be avoided.
Turn on the microscope lamp with the slide switch on top of the case next to the eyepiece. Center the foot of the microscope on the scribed line with the mark about one-quarter inch from the foot directly under the microscope objective. Check the microscope for focus (See Fig. 3). If the image is not clear, it may be brought into sharp focus by turning the focusing screw in the body below the microscope. Check the clarity of the reticle (scale) image in the microscope. If it is fuzzy, unscrew or tighten the chrome eyepiece until it sharpens.
With focusing accomplished, view the intersection of the mark and the cut as shown in Fig. 4. Note how the mark delineates the top edge of the cut. Position the microscope as required to align the left edge of the cut with any convenient long line of the reticle and begin counting the small graduations inwardly (to the right) until the next layer or the substrate is reached. This count divided by the tip designation (2) is the film thickness. If the result should be less than 2 or more than 20 mils, the inspector may wish to utilize 10X or 1X cutting tips respectively.
This may be quickly accomplished by using the knurled- head hex key wrench to loosen the tip set screws. (The wrench is conveniently located atop the switch plate, and serves a dual function as a screw closure for the switch 0" m .02 ‘03 . .03 .07 .02 .09 .10 plate.)
Allow all three tips to bottom in their slots, then pull the selected tip out to 5/16" (approximately) and retighten all tips with moderate finger pressure. Tip changes: Cutting tip designations and appropriate film thickness ranges for each are shown below.