[skyking902001]

Starting a new project and have another question for the experienced guys. In reviewing plans, I notice many areas where the plans indicate to drill either a #40 or #30 hole and then dimple. Many years ago I worked on a project and all holes to be dimpled were drilled to 3/32 or 1/8. After dimpling, the rivet fit nicely thru the hole. Is drilling to finish size and then dimpling the new standard or have I missed something along the way.

Sky

 

[C-GRVT]

I have followed the practice of using a a #41 drill bit for holes that I will subsequently dimple for AN3 contersunk rivets.
This drill size is called out in Van's instructions for the RV-6A and I assume reflects the fact that the dimpling operation expands the hole slightly. I would not use a 3/32" as I think the hole would be too small for the pilot on the dimple (a #40 drill is .098", a #41 is .096" and a 3/32 is .0935").
Bill Brooks
Ottawa Canada
rv-6a finishing kit

 

[skyking902001]

Bill, thanks. As I mentioned, it was many years ago when I had worked on a project-forget a thing (or two or three) since then. I checked over the weekend and neither the dimple die nor the countersink will fit a 3/32 hole, but does fit a #41 hole. I'll probably use a #41 drill for most of the areas that will be dimpled or countersunk.

Sky
8 or 8A?

 

[C-GRVT]

only for dimpling

I think that a #41 drill works well for a hole to be dimpled since the dimpling operation will expand the hole very slightly. Countersinking does not have that effect, so I would use a #40 for a hole to be countersunk. You do not want a hole so small that inserting the pilot of a countersink bit will stretch the hole or a rivet has to be forced in risking scraping a shaving off the rivet that will lodge in the hole or under the rivet.
Bill Brooks
Ottawa, Canada
RV-6A finishing kit