Robot Building for Beginners, Third Edition

CHAPTER 20 ■ COUPLER

Every turn and a half, turn backwards a half turn or so to work excess metal out of the hole. If turning
becomes a struggle, rotate the tap completely out and remove the chips from the tap and hole with a piece of
cloth (not your fingers). A little oil or cutting fluid helps, too.

Inserting the Setscrew

From a hardware store, purchase some #4-40,^1 / 8 -inch long panhead machine screws (see Figure 20-22).
Panhead refers to the shape at the top of the screw. Panhead screws are flat and wide, keeping them near the
shaft while being easy to grasp by hand. Choose either slotted or Philips screw head styles.

Figure 20-22. Finished coupler displaying beautiful screw threads. Alongside, a #4-40,^1 / 8 -inch long panhead
machine screw

Figure 20-21. By turning a T-handle tap wrench, the taper tap starts cutting internal threads in the sides of
the hole in the coupler