HOLE PATTERN TRANSFER
Prevent hole misalignment in mating
parts. By Mose O’Griffin
Illustrations by Tim Lillis
Anyone can stuff a drill bit through a piece of
material, but with a little thought and practice,
you can develop the skill to produce a hole pattern
that allows for accurate mating of parts, to within 2. Use a transfer punch
a few thousandths of an inch (To achieve this level to mark the bottom plate.
of accuracy, you’ll need a drill press; cheap ones To accurately transfer the pattern of holes, put
can be found for about the same price as a nice a ¼"-diameter transfer punch down each hole
battery-operated hand drill.) Follow these guidelines you want to duplicate, and tap it with a hammer
and you’ll produce holes that are right where you (Figure A, next page). The little dimple you make
want them every time. under the center of each hole is a very important
For this example project, let’s say you want to beginning point.
transfer, with precision, a 4-hole pattern, with
¼"-diameter holes, from one ½"-thick steel plate
the 2 plates from moving relative to one another,
such as setting a heavy object on the top plate.
1. Immobilize the 2 plates.
Clamp the top plate to the bottom plate while transferring the pattern, or find another way to prevent
3. Drill a pilot hole.
Before you start drilling, let’s take a closer look at
the common drill bit (high-speed steel, 118° point
angle, 2-flute, “jobber’s length”). Looking straight
down the point, the part inside the small circle is
called the web (Figure B). This part of the bit does