Do you double drill?

[jpurban]

I'm learning about double drilling. Do many of you follow that process?

For example, if you are bucking 3/32" rivet, then first drill out a 3/32" hole. Follow-up with a #40 reamer to properly final size the hole.

[GAHco]

Originally Posted by jpurban

I'm learning about double drilling. Do many of you follow that process?

For example, if you are bucking 3/32" rivet, then first drill out a 3/32" hole. Follow-up with a #30 reamer to properly final size the hole.

I would think you would use a #40 reamer....?

Interesting idea!

[terrykohler]

It would be very easy for Vans to pierce the holes to match the rivet size (aren't they doing that on the 12?). The advantage of a drilled hole is that the "breakout" caused by the shearing of the material during piercing is pretty much eliminated. This gives the rivet a uniform cylinder to expand into rather than missing contact with the approx. 30% of the sheet thickness that is conical in cross section. Reaming just gives you a different size cylinder for the rivet to expand into. The added work probably gives you little or no additional benefit. It'd be interesting if anyone working on a kit has access to a shadowgraph. Picture is worth a 1000 words.
Terry, CFI
RV-9A N323TP

[plehrke]

I ream only holes that require a precision fit like wing attach and hinge fittings. Since rivets expand to fill the hole there is no strength or aesthetic reason to make it a precision hole.

[John Tierney]

I don't double drill, but in his book, Kitplane Construction, Ron Wanttaja promotes undersize drilling for holes that need dimpling, then final drilling to size after the skin is stretched during dimpling, so that the edges of the hole are smooth and line up with the shaft of the rivet.

[krw5927]

I'm not sure there's any benefit to reaming after drilling, if your drill and reamer are the same size. The proper way to use a reamer is to drill slightly undersized and then ream to final diameter. You might just be taking an ugly drilled hole and making it uglier while the reamer bounces around in there.

If you really want to use a reamer, forget drilling and just go through with that #40 (or better yet, for dimpled holes #41) reamer. I've been known to do just that!

[mike newall]

I've stopped match drilling !

The things go together so well initially, the match drilling may actually move holes.

So, on the 8, I am drilling both parts, deburring , clecoing and rivetting.

All working A - OK so far.

[datsclark]

Originally Posted by mike newall

The things go together so well initially, the match drilling may actually move holes.

I thought that was kinda the point of match drilling -- so of the punched holes don't completely line up you move the holes so they do. Otherwise you have some sheer force on the rivet when you set it.

Maybe someone can explain if i'm way wrong?

[az_gila]

Originally Posted by John Tierney

I don't double drill, but in his book, Kitplane Construction, Ron Wanttaja promotes undersize drilling for holes that need dimpling, then final drilling to size after the skin is stretched during dimpling, so that the edges of the hole are smooth and line up with the shaft of the rivet.

Which is a requirement for CherryMax type rivets according to the Cherry data sheet.
Which makes sense since most pulled rivets don't expand sideways like a driven rivet...

[larryj]

To the original post; yes I drill undersize and ream to size all holes, including rivet holes. The reamer makes a nicer hole. "Nicer" being defined as more round, more to size, and better surface finish. In the case of a rivet hole the better surface finish is the most salient point; fewer stress risers. That said, practically speaking none of this is likely necessary. But my observation has been that each of us builds to our own ability and desire. I happen to own a machine shop and understand metal working very well; so it is natural for me to carry the airframe construction a little further than someone else. To anyone that reams their rivet holes to size after drilling I say "good on ya!!"