A tool which I have found works VERY well is one made by Black & Decker....
It is a drill chuck extension which has a sliding smoked plastic cover over
it.....
The drills chuck is taken off the drill motor and re-mounted onto the far
end of the extension shank. The aligning tool's shank is threaded into the
drill motor. The smoked plastic cover has bearings and slides along the
shank.
The six sided plastic cover has three pairs of aligning "notches" along the
end near where the chuck re-mounts...one pair is a half circle, one is a
"V" and the other is a stepped V. The same shape notch appears twice on
the cover - on opposing sides of the six sided guide.
By using the V shaped side you can slide the V up tight with element tubing
and the result is that your drill bit is centered over the tube. Place your
hand on the plastic sleeve - pushing it against your work =>>>> then with
your other hand run the drill motor.
I have used this for assembling yagi antennas MANY times and highly
recommend it. When passing a drill bit all the way through the element I
recommend drill both side of the tube in one pass......if the hole is
"straight" enough for the drill bit then it is straight enough for the bolt
which will go through it!
This drill motor extension is left always attached to one of the drill
motors and is a permanent fixture in W1CW's yagi building arsenal. I do
NOT represent B&D nor stand to gain anything from promoting this tool.
Short of a machine shop with a drill press and v-blocks the average ham
probably will not do any better than this!
73,
Jim, K4OJ
Florida Contest Group - visit our website at:
http://www.4w.com/deemer/fcg.htm
The Florida Contest Group sponsors the Florida QSO Party, check out the FQP
website@:
http://home1.gte.net/wd4ahz/fcg/ssqp.htm
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