Kagasida The substrate should be sufficiently rigid to prevent deformation of the coating during the cutting process. It includes definitions of key terms, reference documents, the significance and use of the practice, and the advantages and limitations of the instruments. This standard is also available to be included in Standards Subscriptions. Coatings astj be applied within a certain minimum and maximum thickness tolerances in order that they can fulfill their intended function.
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A number in parentheses indicates the year of last reapproval. Asuperscript epsilon indicates an editorial change since the last revision or reapproval. Use of theseprocedures may require repair of the coating film. It includes definitions of key terms, referencedocuments, the significance and use of the practice, and theadvantages and limitations of the instruments. Thesubstrate should be sufficiently rigid to prevent deformation ofthe coating during the cutting process.
The surface may be flator moderately curved. Pipes as small as 25 mm 1 in. The values given in parentheses are for informationonly.
It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Referenced Documents2. Summary of Practice4.
Each procedure employs different instruments to makethe cut in the coating. Current edition approved July 1, Published July Originally approvedin Last previous edition approved in as D — 07a.
DOI United States The groove is cut at a precise angleto the surface. Various wedge angles are available. Thisprocedure requires the manual cutting of the coating bydragging a cutting wedge through both the coating and thesurface of the substrate.
In this operation, the cutter trailsmidway between the two guide studs. Continuous 3—pointsurface contact should be maintained to assure precise verticalalignment of the groove. Excessive pressure on the guide studsshould be avoided. Axes of the cavities can be oriented at various angles ofinclination to the surface.
This procedure is similar to Proce-dureAexcept in how the cut is made. This technique eliminatesthe deformations of coating and substrate that may occur whenconventional cutting wedges are used. Hard, brittle, tough,fibrous, tender, or elastomeric materials exhibit clean, non-tearing, controlled disintegration under the rotary cutter. This procedure is commonly usedfor hard, brittle or very thin coatings.
Less damage often resultsfrom the small hole used to measure thickness. Thecutting operation works better on some coatings than on others. For example, elastomeric coatings may close up after cutting. Some plastic coatings may stretch. Other coatings may tear. The cutting process must result in a clearly visible cross-section of the coating or coating system and the substrate. Softor elastic materials can sometimes be cooled or frozen to obtaingood cutting characteristics. With some coatings, improvedcuts can be achieved by wetting the surface, or by speeding orslowing the cutting rate.
Significance and Use5. To be able to compare results obtained by differentoperators, it is essential to measure film thickness carefully. Coatings must be applied within a certain minimum andmaximum thickness tolerances in order that they can fulfilltheir intended function.
Test Specimen6. Coating shall be uniformly applied in accordancewith Practice D or as agreed upon between the contractingparties. Panels shall be placed in a horizontal position duringdrying. Uniform application thickness shall be verified byanother measurement method such as Test Method D orPractice D The scribe cutter and illuminated micro-scope may be combined as a single instrument.
Verification ofinstrument accuracy shall be performed by taking measure-ments on applied films of known thickness see Test MethodD Separate tip designs angles shall provide cuts ofknown slopes such as 1 to 1, 1 to 2, and 1 to These tips shallbe nominally designated 1, 2, and 10 to indicate the ratioof the lateral measurement to vertical depth see Fig.
Thelateral measurement is represented by the reticle markings andthe vertical depth is represented by the coating film thickness. Ensure that the tip aligns vertically with the painted surface fora precisely aligned incision. Ifthickness is unknown, make a trial determination with a 2 tip. Align the scale at right angles to the cut so that thescale divisions are parallel to the cut. Makesure that the smooth cut face of the groove is measured.
Themachined upper edge of the cutting tip usually leaves a lessjagged cut. If multiple coats are observed, individual thick-nesses of each coat may be read.
If thickness is unknown, make a trial determination in2 position. Take care to hold theinstrument at the predetermined angle with sufficient firmnessto prevent sideways movement, as shown in Fig.
The coating thickness is determinedusing the graduations along the long axis of the cut representedby theAand B dimensions in this drawing. Note that the sketchdepicts successive coats and the reticle graduations associatedwith each. The sum of the reticle graduations shall be multi-plied by the appropriate conversion factor for the instrumentangle position used. Use the heavy wheelon hard or thick coatings above microns 10 mils and lightwheel for soft or thinner coatings.
Tighten therecess socket-head screw. Fit the cutterinto the drill hole. Viewthe cut hole with the microscope, focusing on the side of thehole.