OG202
Tooke Paint Inspection Gauge
The Tooke Paint Inspection 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 micro-scopic observation and measurement of substrate and film defects. The Tooke Gauge uses an illuminated 50-power microscope equipped with a “universal scope” with a measuring reticle that accommodates measurement in mils, microns, and millimeters. (Note: Each universal microscope is validated before sale against a certified gage block traceable to the National Institute of Standards & Technology (NIST).) It mounts tungsten carbide cutting tips for precise incision of the work surface. Standard cutting tips are 1×, 2×, and 10×. An optional 5× tip is available. Also, a gauge can be ordered with three tips of the same size, or with a single precision-ground tip and two blanks.
Direct measurement of total coating thickness and thickness of individual coats of paint is a unique capability of the Tooke Paint Inspection 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, cratering, or other microscopic film symptoms.
The new anodized version with the universal microscope
Showing the old style scope
(no longer available)
Operation
A special cutting tool (the “cutting tip”) that is integral to the gauge is used to incise a small precision V-groove through the paint film and into the substrate.
Micro-Metrics Company 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 gauge in standard configuration mounts 1×, 2×, and 10× cutting tips. An optional 5× tip is available. The gauge 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 (in the new style anodized body).
Close-up of a non-standard arrangement of tips;
a 1× tip extended for use and two blanks;
mounted in an old-style gauge body.
Principle: using the new universal microscope
The incised V-groove is observed vertically through an illuminated microscope bearing a measuring reticle (scale). The OG202 is equipped with a “universal scope” with a reticle that accommodates measurement in mils, microns, and millimeters.
Reading the universal microscope
(We’re very sorry, but we do not yet have a professionally done photograph through the new miscrope; we hope to have one soon. This was taken by Elenor. A larger version is also posted.)
Not yet lined up for an actual measurement.
| Smallest hashmark measures in: | 1× tip | 2× tip | 10× tip | |||
|---|---|---|---|---|---|---|
| Mils* | 2 | (1.97) | 1 | (0.984) | 0.2 | (0.197) |
| Microns** | 50 | (50.0) | 25 | (25.0) | 5 | (5.0) |
| Millimeters | 0.05 | (0.050) | 0.025 | (0.025) | 0.005 | (0.005) |
| * 1.0 mil = 0.001" = one thousandth of an inch
**micron = micrometer (µm) = 1,000,000th of a meter | ||||||
The geometry of the Tooke gauge incision
A detailed explanation of the geometry of the Tooke Gauge is now available on this site.
Principle: using the old-style microscope
The incised V-groove is observed vertically through an illuminated microscope bearing a measuring reticle (scale). Both the “English” (Imperial) version with the reticle marked in mils and the metric version with the reticle marked in microns, are no longer available. Micro-Metrics is attempting to have these scopes custom made.
The view through the English microscope
English Reticle Specifications
| Cutting tip |
Maximum Coating Thickness |
Precision of thickness determinations |
One division on the reticle scale represents: |
|---|---|---|---|
| 1× | 100 mils | ± 0.25 mils | 1.0 mil |
| 2× | 20 mils | 0.13 mils | 0.5 mil |
| 10× | 1.0 mil | 0.025 mils | 0.1 mil |
An enlargment of the (English) reticle view showing the divisions
Metric Reticle Specifications
| Cutting tip |
Maximum Coating Thickness |
Precision of thickness determinations |
One division on the reticle scale represents: |
|---|---|---|---|
| 1× | 2500 µm | ± 5 µm | 20 µm |
| 2× | 500 µm | ± 2.5 µm | 10 µm |
| 10× | 75 µm | ± 0.5 µm | 2 µm |
An enlargment of the (metric) reticle
view showing the divisions
The geometry of the Tooke gauge incision
A detailed explanation of the geometry of the Tooke Gauge is now available on this site.
Special applications
The Tooke 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. It 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
| Material: | Machined aluminum body |
| Overall dimensions: | 4.5" x 3.5" x1" 11.4cm x 8.9cm x 2.5cm |
| Microscope: | 50-power, 45-degree, illuminated |
| Power | Two 15V AA drycells, plus two spares |
| Lamp | LED 222 bulb plus spare |
| Cutting tips: | Tungsten-carbide: 1×, 2×, and 10× |
| Shipping Weight: | 2 pounds (0.9 kg) |
The machined aluminum Tooke Gauge comes in a polycarbonate plastic case with two spare batteries, a spare LED bulb, a marking pen, a hex wrench, and a technical data sheet. Standard cutting tip configuration is 1×, 2×, and 10×. An optional 5× cutting tip is also available. Any configuration of tips may also be requested (for example, three 10× tips; or a 1×, 2×, and 5×).
The Technical Data Sheet for the OG202 Tooke Gauge is now available on this site, in a form that can be printed on 8-1/2" by 11" paper.
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