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On 2 Jan 2007 03:34:14 -0800, "Charles" <csa722@aol.com> wrote:
>
>
> Lots of good advice given but there's one problem that hasn't been
>addressed. That's keeping the drill bit in the broken screw and not
>letting it wander off into the spar. if the screw has been broken off
>under flush there's not an easy way of dressing up the surface for a
>good start. To keep from really messing up the job you may want to make
>a drill guide to keep the bit aligned and going straight into the
>broken screw.
> A piece of 1/2" square steel stock about 8" long from any hardware
>store will do. Set it up in a drill ress and drill a hole the size of
>the bit you want to use through one side directly through. Set the bar
>on the spar and line up the hole over the broken screw and then clamp
>the bar down securely to the spar flange. Now you can drill through the
I'd suggest using a "center drill" that just nicely fits the hole
in the steel plate at this point. It won't wander and will create a
nice cone shaped indentation in the screw shank.
Then switch to a drill and metal plate with a hole that fits the
drill. A good sharp drill *should*follow the screw
>bar into the broken screw with far less chance of needing one of those
>special figure eight shaped screws to cover the mess you made.
> Any good quality SHARP drill bit will do the job with the correct
>technique. For drilling out steel screws, use a slower RPM and more
>pressure than for drilling aluminum. Start with a couple of light taps
>at high RPM to ensure the drill gets a good center on the broken screw
>shank or use a small center punch that will fit through the guide.
>Using cutting oil is a good idea.
> I do not think the Craftsman extractors are small enough for a #4
>screw. I'd go with a left handed bit, mouse milk, and take my time.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
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Re: aluminum rib, aluminum spar, holes drilled but screws broken off
