CHAPTER 20 ■ COUPLER
Drilling the Hole for the Setscrew
Simply drill in the location marked earlier. Use a #43 drill bit. If you don’t have that size, you can substitute a
(^5) /
64 -inch diameter drill bit for shallow holes. But, for deeper holes or stronger materials (like steel), you really
must use a #43.
Drill all the way through the tube wall, but not through the tube wall on the other side.
Aluminum drills easily with a Dremel. Brass is slightly more difficult and may require a drop of oil to
aid cutting and chip removal. In fact, after drilling the start of a straight hole in brass using the rotary tool,
I switch to a power drill to finish the job.
Tapping the Hole for the Setscrew
A T-handle tap wrench is the tool that makes the internal threads in a hole for a screw or a bolt. A 4-40 taper
tap (size 4, with 40 threads per inch) is required to finish the setscrew hole in the coupler. Tap and die sets
are available at most hardware stores. Make sure the set includes the standard 4-40 taper thread tap or, if
necessary, purchase it separately.
Carefully insert the taper tap into the start of the hole that was already drilled (see Figure 20-21). Try to
keep the tap as straight and square as possible to the hole. By slowly turning, the taper tap begins to dig into
the metal on the sides of the drilled hole. Be firm, but don’t force it. It twists in, not pushes.
Figure 20-20. Wolfcraft Quick-Jaw vise with a small V groove on the right side