>From: "Richard (Rick) Karlquist" <email@example.com>
>Sent: Dec 28, 2007 12:28 PM
>Cc: TowerTalk <firstname.lastname@example.org>
>Subject: Re: [TowerTalk] Cutting tubing
>This paper technique is also useful if you have to drill
>two holes at 180 degrees apart. Simply mark two lines
>on the paper spaced apart by pi/2 times the diameter.
>For a 2 inch mast, this would be 1.571 inches.
An even easier scheme that doesn't require calculation or measurement... Since
it's hard to accurately measure (and make marks on paper) to thousandths of an
inch, and it requires knowing the diameter of the pipe to that accuracy and
that it's actually circular and not ovaled..
To cross check, you'd put three marks, one at 0, one at pi/2*diameter and one
at pi*diameter, and when you wrap, you make sure the outside marks line up.
However, this is where you can be clever and save yourself the measuring:
Make evenly spaced tick marks (a printed tape measure works, as long as the
ticks are even) and wrap that around, lining up one hole with one tick mark.
You then visually estimate the center between two ticks (one on each side) on
the other side of the tube. If the center mark is numbered 0 and all the
other marks are numbered 1,2,3,4 in both directions, you'd center between two
Hard to describe, but if you try it with a piece of lined paper, you'll see how
it works, and it easily lets you get within 1 mm of the true opposite.
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