Drilling technique question

I am at the step where I am to drill the 11/32 hole in the rear spar doubler inboard…. There is a 3/32 hole already at the location. It nests with the other doubler that already has a 11/32 hole drilled at the location.

Is there a technique to best assure that a 11/32 hole drilled into a 3/32 pilot goes on center? I have a drill press and not running it too fast.

The manual doesn't say to do it but should I drill the piloted piece mated to the already drilled piece? Will the part with the existing hole help line things up?

And finally, later after I assemble the rear spar to doublers prior to mounting on the wing that hole gets reamed out to 3/8 with a reamer. My drill press is high - I'm going to have to support the spar somehow at the right height to get it down on the drill press table - it sure is a long piece!

If anyone got bit on this step somehow I'd like to not reinvent the wheel…….

I'm anxious for a reply as well. I was planning on riveting everything together then using the smaller 3/32" hole as a pilot for my rotacut 3/8" bit. My experience with the rotacut bits is that they leave as clean a hole as a reamer.

drilling

I would avoid drilling in assembly. Chuck a 3/32" bit into the drill press and clamp your work with the bit in the hole. Lift the bit out, make sure it is still lined up, the change to your final bit. All this assumes the pilot is in the correct position. If not, make a drill bushing out of steel tube and drill in assembly as large a hole as possible. Then take apart and step ream to final size.

This is an interesting difference from the RV-10 format for doing this hole. In the RV-10, both parts have the same hole size. You put something in the hold to keep it lined up, you clamp the parts together, then you drill your way up to 3/8". If you had a centering pin that is 11/32" with a point on the end (not sure what they are called, but our machine shop has these), then you could do it the same way, possibly. Center the holes to eachother with the pin, clamp, then match drill carefully with a 11/32 drill bit, or use a bushing that is 11/32OD and a drill bith that fits the ID as a way of stepping up to the right size so the 11/32 bit will go through faster and easier, and will stay centered better. Whatever you do, don't use a Unibit (Stepped drill bit). These tend to wander as they drill, very often ending with a hole that is not concentric with the pilot hole.

I hadn't thought to put the 3/32 in to line it all up but it's obvious once you say it! That takes care of getting the smaller one up to size to match the already 11/32 one.

The 3/8 ream comes in after the rear spar assembly is riveted to the rear spar but before taking the rear spar to the wing ribs. So I think I can do a similar thing when the pieces are riveted together - line up the concentric holes with the 11/32 in place, and then run the reamer through it?..

Really makes me wonder if I shouldn't do the 11/32 hole after it is all riveted together. Or if I make the 11/32 hole leave the shank of the bit in the hole while riveting to make sure the two pieces stay lined up with respect to the hole.

A little of both maybe, but for the most part I think you just got lucky.

Any experienced builder will tell you that clecos are for holding parts together... not assuring alignment.
It is not at all uncommon to cleco together a couple of simple parts with holes for AN470 1/8 rivets, and not be able to get some of the rivets in. If you then uncleco, insert a few rivets to get everything aligned, and recleco, all rivets go in easily.
Because hole diameters get enlarged slightly by dimple countersinking, clecos usually work to get everything close enough when dealing with 3/32 rivets.
When looking for precision (as in a hole reamed for a precise fit of a bolt) clecos are not very reliable for alignment.

Aluminum?

Drilling aluminum requires high speed light pressure.
Drilling steel requires low speed more (higher) pressure.