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Home  >>  Products  >>  Film Thickness  >>  Tooke Gage

Tooke® Paint Inspection Gages


Dual-Measure Scopes - OG212 Gage & OG214 Gage

Meets ASTM D4138-82; ISO 2808

OG202 OG204
Model OG212 (machined-aluminum body) Model OG214 (molded plastic body)

Direct measurement of total coating thickness and thickness of individual coats of paint is a unique capability of the Tooke Gage. It features a Dual-Measure scope, with 1 mil per hashmark space above the line and 20 microns below the line scale. 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 direct observation of microscopic cracking, tendency for brittleness, blistering, cratering, or other microscopic film symptoms.




FEATURES | USE | MORE INFO | PRICE LIST
 

 

Features

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  • Dual-Measure Scope, 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.
  • Models OG212 & OG214 are supplied with 1X, 2X, & 10X cutting tips installed in the gauge body. The 2X tip is shown extended to working position. An optional 5X cutting tip is available.
  • Gauges come in a rugged plastic carrying case with cutting tip wrench, indelible marker, spare LED bulb, and spare batteries.

 

Measuring Procedure

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Open the carrying case and remove the instrument. Check the positioning of the cutting tips. Ensure that the curved cut-out on the side of each cutting tip, the relief cut, is oriented toward the guide studs. This relief cut allows the coating(s) being incised to curl up and away from your incision, making for a cleaner incision. For field use, secure the safety lanyard to the wrist to prevent accidental dropping. As originally supplied, the tip positions will be from top to bottom 1X, 2X, and 10X. The numerals 1, 2, and 10 are engraved in the body alongside each tip respectively. The 1X and 10X tips will be bottomed in the slot, and the operable tip should be extended and secured so the narrow face of the gauge will be parallel to the surface to be incised. In general, this is the correct configuration for making an initial measurement on a film.

An indelible marker is included in the Tooke Gage kit. Marking the top before incising in not required; however it may help determine where to stop counting hashmarks. If you can easily differentiate between the “slope” formed by the incision and the edge marking the top of the coating, marking may not be helpful and can be skipped. Depending, too, on the coating color, other markers may be useful: Wite-Out® for dark colors or a silver- or gold-Sharpie® marker rather than the black one provided, may provided a clearer differentiation. Make a small mark with the marker, if used, at the desired measurement location on the coated 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 for 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 ensure precise vertical alignment of the groove. Excessive pressure on the guide studs should be avoided. The incision does not need to cut deeply into the substrate; merely ensure the substrate is incised along your entire cut.


Fig. 5

Fig. 2. Gauge held in cutting position

Fig. 3. Adjusting Tip Set Screws

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. If the image is not clear, it may be brought into sharp focus by turning the focusing screw in the body below the microscope. This may be quickly accomplished by using the supplied hex key wrench to loosen the tip set screws. Allow all three tips to bottom in their slots, then pull the selected tip out to the correct height, matching the height of the guide studs and retighten all tips with moderate finger pressure.

With focusing accomplished, view the intersection of the mark and the cut as shown in Fig. 4. Note how 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 gage slightly. Nor does it need to be lined up; any hashmark will do.)

 


Fig. 4

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

Fig. 4a.Micrograph of paint film incision.

Fig. 4b. Dual-Measure reticle scale.

The universal scope is no longer available: all Tooke Gages now come with the Dual-Measure scope. However, since the cutting tip angle determines your calculations, using the view through the universal gauge in Fig. 4a shows the same process as through a Dual-Measure scope. "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.

Count the hashmark spaces for each layer of coating. (For instance the top coat, B-to-C, in Fig. 4a is 5 hash wide.) Important: The type of microscope your Tooke Gage is fitted with makes an absolute difference in calculating your measurement.

  • Using the mils-scale on the new Dual-Measure reticle, you divide the number of hashmark spaces by the number designation of the cutting tip. So, if you used the 2X tip to draw your incision, you would divide the 5 hash by 2, which gives your your coating depth in mils (2.5mils). If you used the 1X tip (45-degree face), the ratio is 1:1, so the coating depth would be 5 mils.
  • Using the micron scale on the new Dual-Measure reticle, you use the same division (1x tip = 1:1; 2x tip = 1/2 the counted hash; 10X tip = 1/10 the counted hash) but multiply your calculated count by 20 microns to get your coating depth.
  • Using the older "universal" scope, with its reticle marked in 50microns per hash, you use the same division (1x tip = 1:1; 2x tip = 1/2 the counted hash; 10X tip = 1/10 the counted hash) but multiply your calculated count by 50 microns to get your coating depth.
  • Measurements made using the Tooke Gage are a function of the cutting tip geometry (and not of the microscope). A detailed explanation of the geometry of the Tooke Gage called “Measuring: the Geometry of the Tooke Gage” is available.

 

Principle

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

The easiest example to follow in understanding the principle is demonstrated using the 1X cutting tip. In essence, you are incising a triangle into your coating by cutting the hypotenuse of a right-angle triangle. With the 45° 1X tip, you’re drawing an equi-lateral triangle. (See 1X figure below.) That is, the side of the triangle (/ the bottom of your view), which you are measuring by counting the harshmarks across the ‘cut-width,’ equals the triangle-side that is your coating depth. A 1 : 1 ratio with the 1X tip. With the 10X 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 10X figure below.)



The 1X tip with its cutting face of 45° has a ratio of 1 : 1 so, A = A′ (measured cut A′ : calculated coating thickness A) ("what you see is what you measure").
Ratio: 1X tip: A = A′

The 10X tip with its cutting face of 5° 42' has a ratio of 1 : 0.1 so, A = 1/10th of A (measured cut A : calculated coating thickness A)
Ratio: 10X tip: A = (0.1) A

 

Tip Angle Representation

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Tooke Graph

Diagram of an incision made using a 1X (45°) cutting tip

 

Fig. 1

Diagram of incisions cut by three different cutting tips

 

Reticles

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Please take note: Tooke Gages produced after November 2019 now have the new, custom-designed, custom-manufactured Dual-Measure scope and reticle. Tooke Gages produced between June 2010 and November 2019 are fitted with the “universal” reticle. (See photos below.) The universal scope can be swapped out for the new Dual-Measure scope: contact Gardco for information.

The chart below shows the conversion basis for hashmarks on the universal scale produced between June 2010 and November 2019. For the hashmark conversion using the new Dual-Measure scope, see the Principles section above.


Increment (Hash Mark) Chart - English/Metric
The discontinued "universal" scope conversion.
Note that this table applies ONLY to the discontinued "universal" scope, and not to the new Dual-Measure scope.

Calculating your coating depth as above, using counted hashmarks of the cut-width, visualized through the
"universal" scope, each hashmark for the three main cutting tips will equal:
  1X 2X 10X
Mils 2 (1.97) 1 (.984) .2 (.197)
Microns 50 (50.0) 25 (25.0) 5 (05.0)
Millimeters .05 (.050) .025 (.025) .005 (.005)


Dual Measure Reticle

Universal Reticle

 

Construction

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The OG212 body is made of machined and anodized aluminum. The OG214 gauge body is made of injection molded high-impact plastic. The body holds the microscope and lamp batteries as well as the groove-cutting tungsten carbide cutting tips mounted on the narrow side.

The tripod formed by the two guide studs and the extended / operable cutting tip provides for precise alignment of the cutting tip with the coating surface to be incised. A lanyard and keeper looped through the body secure the instrument to the inspector’s wrist.

A plastic (polypropylene) carry case with foam inserts to carry your Tooke Gage and spare parts: marker, wrench, LED bulb, and spare batteries. The entire unit is designed for convenience and completeness in field inspection tasks.

 

Calibration

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Original factory/OEM calibration of the optics is performed on all gauges when assembled. If OEM certification is desired, it can be ordered at additional cost. Repeat calibration with certification is also available. Contact Gardco for details. Checks are also made with precision applied film standards. For highest precision work, the user is advised to maintain painted panels of known thickness, and to check and calibrate the instrument measurements periodically.

 

Suggestions to Users

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  • On wood or other directional material, make incisions in the grain or “machine” direction to avoid ragged cuts.
  • Soft or elastic materials can sometimes be cooled or frozen with ice or dry ice to obtain good cutting characteristics. An accessory device, the MG402 Microgroover with a precision positioning block that provides an abrasion readable using the Tooke Gage is available. Contact Gardco for details.
  • Dyes or indicator solutions such as phenolphthalein are sometimes helpful to develop appearance contrast between metals (iron-galvanizing) or paint coats.
  • With some coatings, improved cuts can be achieved by wetting the surface, or by speeding or slowing the cutting rate.
  • Coatings with poor adhesion will exhibit a ragged line at the substrate interface. Read thickness from the left incision edge in the SUBSTRATE in these cases. (Note Reference on "Coatings Adherence Measurement..."

 

Special Applications

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The Tooke 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. It is virtually the only tool for measuring paint on plastics.

As indicated above, the quality of the incision in the film discloses much about characteristics of brittleness and adhesion of the material. In addition to the benefits as a dry film thickness gauge, the Tooke Paint Inspection Gage Inspection Gauge (PIG) offers the advantages of a close inspection tool. Abnormalities that would otherwise go undetected by conventional electronic or magnetic gauges include pinholes, adhesion faults, deteriorated substrate conditions, and lack of overall coating integrity. Consider the Tooke Gage Gaug as an excellent adjunct to the conventional DFG and even more useful as a verification tool for the more exotic ultrasonic instruments.

 

CTH01 & CTH02 Cutting Tip Holders

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CTH01 Cutting Tip Holder

The CTH01 Cutting Tip Holder, at a little under two inches (4.1cm) long, allows easy use of a carbide cutting tip without having to manipulate the Tooke Gage Gauge to make the incision and then manipulate the gauge again to view the incision through the microscope. Make multiple incisions with your most-used tip without having to return the gauge to viewing position multiple times.

The cutting tip is secured by two set screws, one on the short end of the holder and one in the side. The wrench provided with OG212 and OG214 Tooke Gage Gauges fits these set screws. The two set screws give 90° support to the cutting tip. The cutting tip storage compartment on the opposite end holds two tips secured by a compartment retaining screw. double cutting tip holder

The CTH02 Double Cutting Tip Holder allows two tips to be mounted on opposite sides and, like the shorter, single cutting tip holder (CTH01), allows easy use of the cutting tips without having to manipulate the Tooke Gauge to make the incision and then manipulate the gauge again to view the incision through the microscope. With this tip holder you can:

double cutting tip holder
  • Make multiple incisions with your most-used tip(s) without having to keep switching the gage to viewing position.
  • Mounting Mount two of the same tips to allow for checking two incisions against each other.
  • "Bracket" your incisions by mounting two different tips to create different incising geometries.




Tips

Replacement tungsten-carbide cutting tips. Available in 1X (45°), 2X (26.6°) and 10X (5.7°) configurations.
An optional 5X tip (11.18°) is also available.

 


Case


DF-OG200-CASE - (included with gauge) Case made of polypropylene with foam inserts to carry your OG212 or OG214 Tooke Gage and spare parts. Has a convenient carry handle, closes securely with two latches and stands upright on two molded feet.

 

References

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  1. "A Paint Inspection Gage" by Raymond Tooke, Jr., OFFICIAL DIGEST, July 1963, 35, pp. 691-698.
  2. "Coatings Adherence Measurement By An Angular Scribe-Stripping Technique" by W. R. Tooke, Jr. and J. Montalvo, JOURNAL OF PAINT TECHNOLOGY, January 1966, 38, pp. 18-28.
  3. "Development of Specifications For Measurement of Paint Thickness On Structural Steel" by J. D. Keene and T. L. Shoemaker, JOURNAL OF PAINT TECHNOLOGY, 45, No. 585, October 1973, pp. 46-67.
  4. "How Instruments Boost Coatings Application Productivity" by W. R. Tooke, Jr., PROFESSIONAL DECORATING AND COATING ACTION, October 1976, pp. 16,18.
  5. "Standard Method of Measurement of Dry Film Thickness of Protective Coatings Systems by Destructive Means", Designation: D4138-82, 1988 ANNUAL BOOK OF ASTM STANDARDS, pp. 695-697.
  6. "Method and Device for Measuring the Thickness of Films" by W. R. Tooke, Jr.

 

Prices

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Prices subject to change    Prices listed in US dollars for domestic shipments within US, Canada, & Mexico only    Export orders require quotations - click here for a quote     For more info call us 1-800-762-2478 or 954-946-9454.
Item Number Item Prices

OG212 - Complete 3 cutting tips (1X, 2X and 10X), plastic carry case, spare LED bulb, 2 batteries, a tip wrench and an indelible marker.

OG214 - Complete 3 cutting tips (1X, 2X and 10X), plastic carry case, spare LED bulb, 2 batteries, a tip wrench and an indelible marker.
DF-OG212 Universal Paint Inspection Gage, Model OG212 (aluminum) $1,095.00
DF-OG214 Universal Paint Inspection Gage, Model OG214 (plastic) 825.00
Accessories/Replacements
DF-OG202-11 EXTRA 1X Cutting Tip 80.00
DF-OG202-12 EXTRA 2X Cutting Tip 80.00
DF-OG202-13 EXTRA 10X Cutting Tip 80.00
DF-OG202-123 1X, 2X, & 10X Cutting Tip Set 250.00
DF-OG202-14 Special 5X Cutting Tip 80.00
DF-OG202-91 CTH01 Cutting Tip Holder (single tip) 66.00
DF-OG202-95 CTH02 Cutting Tip Holder (two- tip) 78.00
DF-OG200-LED LED bulb 7.00
DF-OG200-CASE Plastic Case with spare batteries, marker, tip wrench and LED bulb 40.00
DF-OG212/C Certified OG212 Paint Inspection Gage 1,245.00
DF-OG214/C Certified OG214 Paint Inspection Gage 975.00



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