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Newbie questions: Match drill holes vs enlarge holes

klh1507

I'm New Here
Working on the horizontal stabilizer. Instructions for the spars and doublers said to "match drill" holes. For the ribs on the spars, the instructions say enlarge holes. Do these terms mean the same thing or do I disassemble all the clecoed parts and drill them separately? If drilled while clecoed together, do I need a longer drill bit? (Seems I wouldn't want to push the rib out of the way with the drill.
 
Welcome to VAF!!!

Drill them together. Go ahead and invest in a 12" #30 and #40. They'll come in handy.

Personally I like to use reamers where I can instead of drill bits. Holes come out much cleaner and more precise. There is a debate on them- you might read the forums on pros/cons.
 
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Also you might partially disassemble to match drill. E.g. Remove the forward ribs and match drill the aft ribs. Then remove the aft ribs and match drill the forward through the at-size spar holes. That should get you going without waiting for longer bits. But they will come in handy.

When match drilling sheets, use the reflectivity of the sheet to sight when the bit is perfectly straight. Learned this tip at Osh last year at the cleavland booth-
 
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Thanks...

I ordered long bits and also disassembled parts to drill. Simple solutions like that are what I have to learn. Thanks to both of you.
 
To answer the second part of the question...

Kevin,
Match drilling and enlarging are not the same thing. Match drilling is using the pre-punched hole in one skin/part to make a "matching" hole in another skin/part that you will rivet.

Final drilling is when you have holes in the two skins that already line up - but they are pre-punched a tad small and need to be drilled to the correct size. Final drilling also removes the small burrs made by the punch.

Enlarging is when you have a pre-punched hole that is in the correct place, but is maybe a 3/32" or 1/8" hole and needs to be drilled to 3/16" for a bolt to fit thru. That saves you from having to measure where the hole needs to be - you just have to drill the hole up to size.

Hope that helps... keep working :)
 
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