OG204 Plastic Tooke Paint Inspection Gauge

OG204 Tooke Paint Inspection Gauge

The OG204 Tooke Paint Inspection Gage/Gauge is a precision tool for inspection and thickness measurement (in accordance with ASTM D4138) of single or multiple coats on any substrate, and for microscopic observation and measurement of substrate and film defects. The OG204 Tooke Paint Inspection Gage/Gauge uses an illuminated 50-power microscope with measuring reticle, and mounts tungsten carbide cutting tips for precise incision of the work surface.

Direct measurement of total coating thickness and thickness of individual coats of paint is a unique capability of the OG204 Tooke Paint Inspection Gage/Gauge. Thus, in addition to routine use, the OG204 Tooke Paint Inspection Gage/Gauge  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, cratering, or other microscopic film symptoms.

Construction

The gage body is a injection-molded high-impact polycarbonate plastic. It contains the microscope and lamp batteries and the groove-cutting tungsten-carbide cutting tips mounted on the narrow side. Two adjustable threaded guide studs project from the body on the same side as the cutting tips. The tripod thus formed by the three legs (guide studs and cutting tip) provides precise alignment of the tool with the surface to be grooved. A lanyard with keeper looped through the body secures the instrument to the inspector’s wrist. The entire unit is designed for convenience and completeness in field inspection tasks.

Operation

A special cutting tool (the “cutting tip”) that is integral to the gage is used to incise a small precision V-groove through the paint film and into the substrate.

Incising the V-groove with the OG202

The cutting tips are precision-ground by hand from tungsten-carbide blanks in a multiple-step process that includes a final inspection by microscope for accuracy of angle, fineness of finish, and lack of chips and damage.

1×, 2×, and 10× cutting tips

The gage in standard configuration mounts 1×, 2×, and 10× cutting tips. An optional 5× tip is available. The gage can also be ordered with three tips of the same size or in any desired configuration (including a single cutting tip with two non-functioning blanks).

The tip slot is marked for the standard tip arrangement

Close-up of a standard arrangement of tips;
showing2× tip extended for use.

Principle

The incised V-groove is observed vertically through an illuminated microscope bearing a measuring reticle (scale). An “English” (Imperial) version, with the reticle marked in mils, and a metric version, with the reticle marked in microns, are available.

The view through the English microscope

An enlargment of the (English) reticle view showing the divisions

Metric Reticle Specifications

An enlargment of the (metric) reticle
view showing the divisions

The geometry of the Tooke Gage incision

Special Applications of a OG204 Took Paint Inspection Gauge

The OG204 Tooke Paint Inspection Gage/Gauge has been used to assess sandblast cleaning work, to measure plating and paint thickness on ceramics, metal, wood, and concrete, and even to measure protective backing thickness on mirrors. The OG204 Tooke Paint Inspection Gage/Gauge is virtually the only tool for measuring paint on plastics. The quality of the incision in the film discloses much about the characteristics of the brittleness and adhesion of the material.

Shipping Specifications

The injection-molded high-impact polycarbonate plastic Tooke Gage/Gauge comes in a case with strap, spare batteries and bulb, marking pen, hex wrench and a technical data sheet. Standard cutting tips are 1×, 2×, and 10×.

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