DEDENDUM (fig. 3-1). The distance between thepitch circle and the bottom of the tooth space.WORKING DEPTH (fig. 3-1). The depth to whichthe teeth of a gear enter into their mating space.CLEARANCE (root) (fig. 3-1). The distancebetween the top of a tooth and the bottom of itsmating space.WHOLE DEPTH. The total depth of the toothspace and also the sum of the addendum anddedendum.INTERFERENCE. Contact between mating gearsat some point other than along the line of action.FILLET (fig. 3-l). The concave radius that joinsthe tooth profile and the bottom of the tooth space.Tests and inspections according to the PMS areminimum requirements only. When defects aresuspected, or operating conditions indicate, inspectionsshould be made at more frequent intervals.When opening gear cases for inspection, useextreme care. Even under normal conditions, when thecovers are lifted the possibility of getting foreignparticles inside the gear case is high. The engineerofficer should evaluate all ongoing work in the engineroom, especially in the areas over the gears. Besidesevaluating the work, the engineer officer must scheduleall necessary MRG inspections.You must be sure that gear sumps are cleaned afterall work to the MRG has been completed. Thoroughlyinspect the gear sump and remove any foreign material.Absolute cleanliness is required before filling the gearsump with clean oil.Oil should be renovated before returning it to thesump. If new oil is used, you must be careful to removeany water or foreign particles. Cloth bags placed in thelube oil (LO) strainer baskets after major repairs isanother required precaution. The bags stop foreignparticles from passing through the gear train andbearings. Once the proper temperatures and pressureshave been reached in the LO system, inspect the MRGfor leaks and all sight-flow indicators for proper flow.The following paragraphs discuss some of theinspections, tests, and problems that may occur toMRGs.BACKLASH.— Backlash is the play between thesurfaces of the teeth in mesh measured at the pitch circle.The backlash will increase with wear, and can increaseconsiderably without causing trouble. On some gearsthat are recut, the backlash does not affect operation orFigure 3-1.—Gear tooth nomenclature.3-2
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business