+ :title [choosing drill bit]
+ (p [the arduino comes with holes in it already, so we will make
+ some choices around those holes.
+ 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.
+ there are two constraints between the hole and screw.
+ each hole needs to be big enough for the screw body to fit
+ through it.
+ the holes also need to be smaller than the screw's thread.
+ since there are holes on the arduino already, the screw was
+ chosen to match it.
+ the screw was chosen so that the hole on the arduino was
+ bigger than the screw body and smaller than its thread.
+ we will choose the biggest drill bit that fits through the
+ hole on the arduino, then use that to drill holes in the
+ deck.])
+ (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")))
+ (p [check
+ ,(itemize
+ (item
+ [what would happen if the drill bit were larger than the
+ screw thread?])
+ (item
+ [what would happen if the drill bit were smaller than the
+ screw body?]))]))
+ (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.])
+ (p [check
+ ,(itemize
+ (item
+ [where should the teeth clamp down on the drill bit?])
+ (item
+ [what would happen if the teeth tightened on the recessed
+ part of the drill bit?]))]))
+ (subsubsection
+ :title [holding drill]
+ (p [hold the drill with one hand on the handle and trigger.
+ put the other hand on the orange nozzle, before the
+ black spinning part.]))