From the Schoolcraft Skyhawks, Portage, Michigan
Drilling Bolt Holes
by Rick Giannini, Desert Hawks R/C Club
On most of the glow engines we use today, the
propeller reamers that are currently available
usually work for propeller hole enlargement.
However, when we move up to larger engines, there is
a need for a hole larger than the reamer is capable
of making.
If you have a drill press, try this:
•
Move the drill plate off to the side a few degrees
so the hole is not under the bit chuck.
• Drill and
tap a hole for a ¼-20 bolt.
• Thread a ¼-20 bolt up
from the bottom of the plate roughly ¼ to 3/8 of an
inch.
• Bevel the end of the bolt with a ¼-inch bit.
• Set a new propeller over this short alignment pin
(bolt) and accurately drill the larger propeller
hole.
• Center the pin using the beveled tip of your
drill bit to align it.
• Drill about halfway down
the propeller hole, move your plate back to the
regular position, and continue to drill through the
propeller.
• Hold the spinner firmly to prevent
spinning.
If your engine uses a multibolt hub, the
front plate usually has a short-threaded post for a
spinner bolt. This post is conveniently the same
size as the factory centered hole on a big wooden
propeller. Put the front plate on the propeller with
the post in the hole and drill the outer holes as
needed.
I suggest that if you are drilling larger
propellers, you use a drill press. If you try this
by hand, it is practically impossible to get an
accurate hole, and on larger propellers, you get a
lot of vibration from an inaccurately centered hole.
Q
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