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Matching holes

nzrv8

nzrv8

Well Known Member
Hi Guys,

Have you got any tips for drilling an old elevator centre bearing hinge bracket assembly to a new HS rear spar? The holes in the steel bracket are already 3/16", one of the new spar holes is reamed to 3/16" so I can slide a bolt in there to hold things steady, but the other 3x holes (drilled up to approx .150) are misaligned. I don't think a drill bushing will work as it would have to be very thin. Maybe clamp in the drill press? I can easily order new brackets for $15 and drill them to the spar, but I enjoy a challenge, and I'm always keen to learn new tips.

Cheers!
 

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Match drilling

nzrv8 said:
Hi Guys,

Have you got any tips for drilling an old elevator centre bearing hinge bracket assembly to a new HS rear spar? The holes in the steel bracket are already 3/16", one of the new spar holes is reamed to 3/16" so I can slide a bolt in there to hold things steady, but the other 3x holes (drilled up to approx .150) are misaligned. I don't think a drill bushing will work as it would have to be very thin. Maybe clamp in the drill press? I can easily order new brackets for $15 and drill them to the spar, but I enjoy a challenge, and I'm always keen to learn new tips.

Cheers!
Click to expand...

Try this.
 
Make an 3/32 to 1/8” shim that will fit inside the bolt pattern between the two parts. Tighten the one bolt and clamp the opposite side. The steel hinge bracket will support the body of the drill and the shim will give clearance for the drill point. match drill the remaining holes. If the holes are far off center it might help to use a needle file to get them closer to concentric.
 
Last edited:
You could drill it out for an AN4 or 1/4” bolt. I would much rather have a good clean hole instead of shimming and there is a lot of metal there to except a larger bolt.
 
Resolved!

Thanks for all of the suggestions. I tried turning up some brass bushings, but the wall thickness was just too thin. I then spaced the hinge brackets up off the spar as per MikeyB's advice, and it worked a treat! Sometimes the best solution is the simplest one.

Cheers!
 

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Glad it worked out! When I've been faced with this situation, I've clamped everything up tight in the drill press and used an endmill. An end-cutting endmill won't follow an off-center hole. You would of course use a size smaller than the finish diameter.
Stewart, 6
 
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