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  #1  
Old 12-01-2014, 07:58 PM
JDA_BTR JDA_BTR is offline
 
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Location: Baton Rouge, LA
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Default 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…….
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  #2  
Old 12-02-2014, 06:44 PM
joatmon joatmon is offline
 
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Location: Waupaca, WI
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Default

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.
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  #3  
Old 12-02-2014, 07:06 PM
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Andrew M Andrew M is offline
 
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Default 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.
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  #4  
Old 12-02-2014, 07:38 PM
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Jesse Jesse is offline
 
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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.
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  #5  
Old 12-02-2014, 08:14 PM
JDA_BTR JDA_BTR is offline
 
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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.
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  #6  
Old 12-04-2014, 07:31 AM
Tom023 Tom023 is offline
 
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Location: Cypress, TX
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Default Just lucky or the 14 kit is just that good...

I have to admit this thread made me a little nervous in that I may have screwed up my rear spar attachment point. I don't have a drill press so when the plans said to drill the 3/32 hole to 11/32, I put the doubler plate in the vise, chucked an 11/32 bit in my hand drill and slowly drilled the hole. Then I clecoed it to the rear spar fork using the 24 1/8" clecos, figuring the clamping force with that many in a 5"x5" area would keep everything aligned. Off to my friend's $100K milling machine for the 3/8 reaming. I separated the parts, primed them and then riveted everything to the rear spar. I never checked the alignment of the two 3/8" match reamed holes after riveting, so even though you are suppose to ream them after being revited to the spar, I did it before figuring surely those 24 clecoes will keep everything in order, or not? I stopped at the hangar last night and inserted the 3/8 reamer into both the left and right assemblies. The reamer fit perfectly and the hole measured out to 3/8. If there was any misalignment between the two plates I doubt the reamer would go through both holes, catching on the lip where the two parts would be misaligned. Maybe I got lucky or this kit is so precise that it's hard to screw up. Maybe a little of both.
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  #7  
Old 12-04-2014, 08:25 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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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.
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  #8  
Old 12-04-2014, 09:34 AM
Tom023 Tom023 is offline
 
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Probably so. As they say, "I would rather be lucky than smart". Seems like everytime I overthink something in the plans it just get me into trouble.
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  #9  
Old 12-04-2014, 10:51 AM
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Default Aluminum?

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