All machines bosses should be masked before painting. Do
not paint areas under hold down nuts where torque is re-
quired.
3-29. Aluminum and Steel Parts. Parts shall be cleaned and degreased prior to painting. Apply one coat zinc chromate primer, thinned with approximately two parts toluene, and air dry. Apply one coat of enamel and bake at 250°F., to 300°F., for one-half hour. Enamel may be allow-ed to air dry but an inferior finish will result. Parts from which paint has not been removed may be repainted omit-ting the primer coat.
3-30. Magnesium Parts. Magnesium parts should be clean-ed thoroughly with a dichromate treatment prior to pain-ting. This treatment consists of cleaning all traces of oil and grease from the part by using a neutral, non-corrosive degreasing medium followed by a rinse. After which the part is immersed for 45 minutes in a hot dichromate solu-tion (3/4 lbs. of sodium dichromate to one gallon of water at 180°F. to 200°F., quantity as required). The part should then be washed thoroughly in cold running water, dipped in hot water and dried in an air blast. Immediately
thereafter the part should be painted with a prime coat and engine enamel in the same manner as prescribed for aluminum parts.
3-31. Shroud Tubes. Shroud tube should be thoroughly cleaned and dipped in zinc chromate primer thinned to spraying consistency. After the primer is dried the shroud tube should be painted on the outside with engine enamel.
3-32. All paint applied in the foregoing operations should preferably be sprayed; however, if it is necessary to use a brush, care should be exercised to avoid an accumulation of pockets of paint.
3-33. Replacement of Studs. Any studs which are bent,
GeneralOverhaul
broken, damaged or loose, must be replaced. The method of removing studs depends on the type of stud and man-ner in which it is broken. The procedure for removing and replacing studs is as follows:
a.
If there is sufficient thread area available on stud, use a collet grip tool consisting of a tapered collet that threads onto stud and a housing that slips over the collet. Tighten bolt on top of the housing and draw collet into housing to lock puller on the stud with a tight grip.
b.
If the collet type tool cannot be used, drill a small hole into the stud. Employ a pilot bushing to guide drill into center of stud when stud is broken beneath the surface of the crankcase. Redrill the hole to enlarge it to ac-commodate the proper size extractor. Using the extrac-tor, remove the stud.
c.
After studs have been removed, check for size and condition of threads in stud holes to determine whether oversize studs must be used for replacement. Coat threads of studs with thread lubricant. Specification JAN-A-669, and drive stud to correct depth by using a suitable stud driver.
3-34. Corrosion-Prevention. At the conclusion of all repair operations and subsequent inspection, coat all steel parts with preservative oil. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：莱康明发动机大修手册 OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES(10)
