T.O. 33B-1-12-27Table 2-3. Mechanical Working Processes.METAL REMOVALABRASIVE BLASTINGFiling SandSanding Aluminum OxideScraping Glass BeadMilling Plastic Media BeadsDrillingLigno-CelluloseReamingShot PeeningGrinding Metallic GritLiquid Honing Organic MediaVibratory/Tumble Deburring2.3.6.2 EffectsOfMechanicalWorking.NOTEIf a conflict arises pertaining to the proper inspection method to use followingmechanical working, the appropriate engineering activity SHALL be contacted forfinal determination.Mechanical working removes soils and contaminates by physical action. This physical action may also remove ordeform the part surface. Deformation is in the form of metal flow or displacement on the part surface. The amount ofdeformation depends on the type and severity of the working plus the ductility of the part. Even a small amount ofdeformation, such as that caused by fine sanding or vapor blasting, may reduce the surface opening of smalldiscontinuities. This deformation can reduce the effectiveness of the penetrant inspection process. Chemical etching(see paragraph 2.3.5.13) may be necessary when penetrant inspection is performed after a less severe mechanicalworking process. Severe mechanical working processes, such as metal removal, shot peening, or grit blasting, can sealor close the surface openings of large discontinuities which prevents the formation of penetrant indications. Penetrantinspection SHALL be accomplished prior to mechanical work processes, such as machining, shot peening, grit blasting,plastic media bead blasting, or coarse sanding, that severely displace surface metal. If it is not feasible to performpenetrant inspection prior to these processes, then another inspection method should be considered. An exception tothis requirement is when penetrant inspection is performed to detect discontinuities formed by mechanical working,such as machining tears or grinding cracks.2.3.7 Precleaning.2.3.7.1 SolventCleaningWithAerosolSprayCans.CAUTIONIsopropyl alcohol and most Class 2 solvent removers are flammable.
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