Standard Aircraft Handbook - Some Questions

[TThurston]

I purchased a copy of "Standard Aircraft Handbook for Mechanics and Technicians" (sixth edition) from Van's Aircraft. I've been reading sections in it with the idea that it would keep me on track regarding what to do and not to do. A couple of statements surprised me:

Page 87: "Drilling operations cause burrs to form... Removal of these burrs ... must be performed if the burrs tend to cause a separation between the parts being riveted. Burrs under either head of a rivet do not, in general, result in unacceptible riveting."

Page 87: "Deburring shall not be performed on predrilled holes that are to be subsequently form countersunk". On page 91 it explains that "form countersinking" is another term for what we call dimpling.

It sounds like this handbook recommends far less deburring than I had understood was required. Any comments?

[terrye]

The same wording exists in the "Standard Aircraft Handbook" in the earlier fifth edition I have, but I don't believe it represents good practice. My copy of Jeppesen's A&P Technician Airframe Textbook (1992 edition) P. 215 states:

"When aluminum alloys are drilled they usually leave sharp burrs on the edge of the hole, and unless these are removed, the pieces will not fit together closely enough to give us a good riveted joint....you do not want to countersink (the hole) just cut the burrs off of the edges."

I also believe cracks will propagate easier from the thin edge of a burr than from a deburred hole.

The instructions in the Van's manual I believe represent good workmanship practice, that is deburr every hole before dimpling or riveting.