+ :title [choosing drill bit]
+ (p [choosing the right drill bit depends on what job you are doing.
+ right now, we are making holes for screws to hold the
+ arduino to the deck.
+ this means the hole needs to be big enough for the
+ screw body to fit through.
+ we want the screw to stay put once it's in place.
+ we also want the drill bit to be smaller than the
+ diameter of the thread.
+ the screw was chosen so that the hole on the arduino
+ was bigger than the body and smaller than the thread.
+ we will choose the biggest drill bit that fits through
+ the hole on the arduino.])
+ (p [here's a cross section of a screw in the deck]
+ (figure :legend "screw cross section"
+ (image :file
+ "arduino-to-deck/screw-cross-section.png"))))
+ (subsubsection
+ :title [inserting drill bit]
+ (p (figure :legend "arduino to deck / insert bit"
+ (image :file "arduino-to-deck/1-insert-bit.png"))
+ [insert the drill bit into the teeth of the drill.
+ insert it far enough that the teeth will clamp on the
+ smooth part of the bit when they are tightened.])
+ (p (figure
+ :legend "arduino to deck / twist tighten drill teeth"
+ (image :file "arduino-to-deck/2-twist-tighten-drill-teeth.png"))
+ [while holding the drill bit, twist end of the drill to tighten
+ the teeth.
+ make sure that the teeth end up gripping the flat part of
+ the drill bit.]))