Hole Drilling Through Fittings

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Kyle Boatright

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What's the best way to match drill holes between dissimilar materials particularly wood and steel, where you're probably not going to drill through the entire stackup at once.

For instance, how would you drill the common holes that attach a steel spar fitting to a wooden spar, where you probably want to use a HS bit on the steel, and a forstner bit on the wood, and it is critical to maintain alignment all the way through the assembly?
 

goldrush

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Slightly different problem, referring to drilling holes in the end of a long replacement ( 20mm square 1m long) outer box section tube, which fits over a stub inner with no access to "sealed" end pf the stub, to take "fitted" bolts .
The inner stub having been already drilled, the outer being new and has no pilot holes etc etc. Thus, there is no way of assembling and then marking through the original holes in the stub from the inside, the original outer tube having been "lost":-(
Can't think of any way except transferring very accurate measurement from one to the other.
 

TFF

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If you did not leave the box spar open for drilling, you can make a temporary spar jig that is open for drilling. Duplicating the finished spar.
 

Hot Wings

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Can't think of any way except transferring very accurate measurement from one to the other.
Can you fabricate and mount a drill guide to some other structure near the hole to be matched? If so align that guide with the original hole then slide the new part into position and drill.
 

goldrush

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TFF............... don't think that idea will work in this case, but Hot Wings.. that has given me a probable way to go... fabricate a jig on the existing holes with removable spacers to represent the outer tube.
i.e 4 separate "loose" drilled plates, ( 2 spaced through holes involved) bolted through the existing holes (that way the positions of the holes in the plated are not critical, the original holes being on the "inside") with the spacers in position to represent the "missing tube" ...then weld/braze/fix the plates in position... remove the spacers......... insert tube.....
drink a bottle of Single malt......... keep all legs and arms crossed................ close one eye, hope, pray and DRILL:)
 

Hot Wings

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close one eye, hope, pray and DRILL:)
If you're really paranoid maybe bush the jig and drill next size down. Then put a temporary bushing in the original hole to make sure everything lines up with an undersized bolt? Even if this isn't possible, bushing the jig and drilling undersize helps to keep the final drill from wandering off center.
 

Kyle Boatright

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Pops

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I looked at that method/thread. Is there any reason not to make one "large" tool and use bushings to reduce the ID to the appropriate drill diameter for the application? That way, you'd only need one weldment.
You will want the jig to be as close as possible to the fittings for better accuracy.
Dan
 
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