OG212 Dual-Measure
Tooke® Paint Inspection Gage

 

The OG202 Tooke Paint Inspection Gage is a precision tool for inspection and dry-film 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.

Dual-Measure features

  • Dual-Measure scope, with 1 mil per hashmark space above the line and 20 microns below the line scale.
  • 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.
  • Both the OG212 and OG214 are supplied with 1×, 2×, and 10× cutting tips installed in the gauge body. An optional 5× cutting tip is available.
  • Gauges come in a rugged plastic carrying case with cutting tip wrench, indelible marker, spare LED bulb, and spare batteries

The Tooke Gage uses an illuminated 50-power microscope equipped with the Dual-Measure microscope with a measuring reticle that accommodates measurement in mils, microns, and millimeters. The gage mounts three tungsten carbide cutting tips for precise incision of the work surface. Standard cutting tips are 1X, 2X, and 10X. (An optional 5X tip is available.) Also, a gauge can be ordered with any three tips desired, or with a single precision-ground tip and two blanks.

Dual-Measure scope testimonial

Oct 2019: Peter M., Product Quality Manager at a major industrial client:

The new reticles are AMAZING!

I have 2 more [gauges for scope swaps] in the mail for you and would like to purchase a new gauge as well.

FYI, I plan to purchase one more new one after this and will also send another 2 for new scopes after I get these back; that should take care of us.

Thanks again, these are AWESOME!

I can add that I took the Tooke to the line and watching my inspectors use the new gauge was like watching my kids at Christmas.

Direct measurement of total dry-film coating thickness and thickness of individual coats of paint is a unique capability of the Tooke Paint Inspection Gage. Thus, in addition to routine use, it often serves as a “referee” instrument to calibrate indirect or non-destructive thickness measuring instruments.

(Note: Each microscope is validated before sale against a certified gage block traceable to the National Institute of Standards & Technology (NIST). An OEM calibration certificate is available for an additional fee.)

Special applications

The Tooke Gage 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.

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 anodized Dual-Measur OG212 microscope reticle is marked in mils and microns.OG202

The aluminum gauge body contains an illuminated microscope and mounts three tungsten-carbide cutting tips (that incise the “V-groove” for measuring) on the narrow side. Two 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.

The old-style scope (not currently available)
More information about this gauge is posted elsewhere.

OG202

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.

Ensure the operable tip and both guide studs are in solid contact
when incising the V-groove with the anodized OG212 Tooke Gage
using the OG212
Incorrectly incising the V-groove with the anodized OG212 Tooke Gage.
Notice the closer guide stud is not touching the surface. using the OG212

Tooke Gage cutting tips are precision-ground from tungsten-carbide blanks.

Cutting tips are precision-ground from tungsten-carbide blanks.

The gauge in standard configuration mounts 1X, 2X, and 10X cutting tips. (An optional 5X tip is available.) The gauge can be ordered in any desired configuration, such as with three tips of the same size. You may also order (for a lower price) a gauge with only a single cutting tip and two blank tips (spacers).

The tip slot is marked for the standard
tip arrangement (in the anodized body).
close-up of tip slot
Close-up of the 1X tip extended for use and two blank tips;
mounted in a (very) old-style gauge body.
tips mounted in a 202 gauge

Principle: using the Dual-Measure microscope

Measurement with a Tooke Gage is a function of
the cutting tip face-angle and NOT of the microscope.

One of the best things about the new Dual-Measure scopes is the return to an easy calculation system related to the cutting tip face-angle. As described in the measuring demo above, you count the hashmarks spaces for each layer of coating, and then calculate the coating depth using the the Dual-Measure scope conversion shown below.

 Conversion for the
Dual-Measure scope
Cutting tip used:Each counted hash =
1×1 mil
2×1/2 mil
10×1/10 mil
View through the new Dual-Measure reticle
view through the Dual-Measure reticle
The discontinued universal microscope reticle is marked in 0.05mm (50µm) per hashmark

For the scope conversion for the discontinued “universal” scope, see the Reticles section below.

Reading the Dual-Measure microscope

Note that in the photo below, the zero-line of the reticle is not lined up for the actual measurement (nor does it need to be; any hashmark will do). The gray/silver-colored “line” is the metal substrate; the white “line” is the (inside of the) green coating, which is what is measured visually through the scope. (See below for a different annotated version.) The cutting tip “draws” the (specifically-angled, depending on the chosen tip face) incision, which allows for calculation of the coating thickness. In this photo, the black marker has not been used to make the edge (top) of the green coating more easily seen.

The view through the universal microscope

In the next photo, the “zero-line” of the reticle is not lined up with the edge of the primer coating (the white line to the left of the zero-line); it is approximately centered in the substrate (gray/silver line). (This was not intentional; lining up the camera moved the gauge slightly. Nor does it need to be lined up; any hashmark will do.) “Line A” is on the edge between the substrate and the beginning of the primer-coating: begin your measurement there. “Line B” marks the top of the primer coating/beginning of the top coating (light blue). “Line C” is the incision into the top coating, made easier to see by using the black marker provided with the Tooke Gage.

Annotated close-up through universal scope
Thus, in this photo and using the discontinued “universal”
scope with 50µm per hashmark space,
the thickness measured for each tip equals:

1 X tip

  • “white primer” = 2 reticle/hashmark spaces = 100µm
  • “blue topcoat” = 5 reticle/hashmark spaces = 250µm

2X tip

  • “white primer” = 2 reticle/hashmark spaces = 50µm
  • “blue topcoat” = 5 reticle/hashmark spaces = 125µm

10X tip

  • “white primer” = 2 reticle/hashmark spaces = 10µm
  • “blue topcoat” = 5 reticle/hashmark spaces = 25µm

(If you have an older gauge, with an English-only or metric-only reticle, please see this page for the measurements that would apply to this incision. These old-style scopes have a green-anodized barrel.)


The geometry of the Tooke Gage incision

In essence, you are incising a triangle into your coating by cutting the hypotenuse of a right-angle triangle. The easiest example of the process is demonstrated using the 1× cutting tip. With the 45° 1× tip, you’re drawing an equi-lateral triangle. (See 1× figure below: 1× tip has a 1 : 1 ratio.) That is, the “bottom” side of the triangle (your view through the microscope) that you are measuring by counting the hashmarks across the ‘cut-width,’ equals the triangle-side that is your coating depth. With the 10× tip, you’re drawing a right-angle triangle, and one-tenth (1/10) the number of hashmarks across the cut-width is your coating depth. (See 10× figure below.)

Cutting tip diagram and
ratio of cut-width : coating-depth

A′ : A = 1 : 1

A′ : A = 1 : 0.5

A′ : A = 1 : 0.2

A′ : A = 1 : 0.1

A detailed explanation of the geometry of the Tooke Gage called “Measuring: the Geometry of the Tooke Gage” is available.

 

Replacement tungsten-carbide cutting tips.

Available in 1× (45°), 2× (26.6°) and 10× (5.7°) configurations. An optional 5× tip (11.18°) and blank unfaced tips are also available. (The blank tips provides lateral stability for the operable tip, if only one faced tip is used.)


Shipping specifications

The machined aluminum Tooke Gage comes ready for use in a polycarbonate plastic carry case with two spare batteries, a spare LED bulb, a indelible marking pen, a hex wrench, and a technical data sheet.

  • Standard cutting tip configuration is 1X, 2X, and 10X.
  • An optional 5X cutting tip is available.
  • Any configuration of tips may be requested (for example, three 10X tips; or a 1X, 2X, and 5X).
  • You may also order (for a lower price) a gauge with only a single cutting tip and two blank tips (spacers).

Specifications

Material:Machined anodized aluminum body
Overall dimensions:4.5" x 3.5" x1"
11.4cm x 8.9cm x 2.5cm
Microscope:50-power, 45-degree, illuminated
PowerTwo 15V AA drycells in the gauge,
plus two spares
LampLED 222 bulb plus a spare bulb
Cutting tips:Precision-ground tungsten-carbide:
  1X, 2X, and 10X (or as desired)
Shipping Weight:~2 pounds (0.9 kg)

Documentation

The Technical Data Sheet for the OG202 Tooke Gage is available to be printed on 8-1/2" by 11" and A4-sized paper.
and
A detailed explanation of the geometry of the Tooke Gage called “Measuring: the Geometry of the Tooke Gage” is available.

Website design and management provided by SnowTao Editing Services.

A (slightly pained) comment (by an overly fastidious technical editor) on spelling:   In the American coatings industry, the word gauge is usually spelled “gage.” Because the Tooke Paint Inspection Gage is – and always has been – known by this spelling, I have used that spelling in the proper name of the gauge, but not elsewhere.