Primer in close tolerance holes

[york]

Is it common practice to omit primer application inside close tolerance holes drilled in aircraft flight control parts such as bellcranks? The engineering drawing for this part doesn't specifically omit primer application in the holes.

D. York

 

[jetmaker]

york,

From my experience, primer is omitted in close tolerance holes because installation of the fastener can strip the primer off, leaving you with a non-uniform contact region and looser fit than desired. If you are concerned about corrosion, due to environment or dissimilar materials, suggest wet installing the fastener, changin fastener type to a plated one compatible with your base material, and/or externally sealing to protect against moisture intrusion.

Have fun.

 

[HSThompson]

york,

Ditto to jetmaker's comment. I might also add that since by definition c/t holes are meant to be a "tight" fit, adding primer will make fastener installation very difficult. I agree with, and often use, wet installation with primer or sealer as the situation requires.

 

[johnfalky]

Also a "heads up" If you're in Aircraft Maintenance Engineering, putting paint in fastener holes is a trick used by marginal technicians to disguise a discrepancy condition.