Page 77 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

58 Making Things Move

2. Use the center punch to make a mark where you want to drill. This is not
strictly necessary, but will prevent the drill bit from wandering when you start
drilling the hole.

3. Clamp the aluminum down to your worktable. Install the 0.089 in drill bit in
your drill, and drill a hole either partway through the material (blind hole) or
all the way through (a through hole is much easier to tap). You will need to
clamp or hold down your scrap aluminum while doing this, depending on
its size.

4. Clear off any metal chips or burrs from the hole with your file or countersink
tool.

5. Spray or squirt some tapping fluid or WD-40 on the hole. Although not strictly
necessary, this will make your job easier and decrease your risk of breaking the
tap. It’s much harder to tap a dry hole.

6. Install the tap in the tap handle, just as you would insert a drill bit into a drill.

7. Place the end of the tap in the hole you just drilled, and position the tap
perpendicular to the material (see Figure 3-4). The tap must stay perpendicular
to the material surface the whole time or it will break. Carefully turn the tap
handle clockwise one or two turns until you feel the little teeth on the tap
start to bite into the aluminum. From this point on, turn the handle one-half
turn clockwise, then one-quarter turn counterclockwise. This backing up is
necessary to cut the aluminum in small pieces so the chips don’t build up, plug
up the tap, and cause it to break.

CAUTION Taps are made of material that is very strong and sharp, but
very brittle. They will break surprisingly easily if you twist too hard. Don’t try
to correct for misalignment once you’ve started to tap the hole.