机ji1 the first machines were made of wood 木mu4。 几ji is a tea-table. Here however the tea table character is reused to indicate the bow of a disassembled crossbow. If you put the 几ji1 over the 木mu it makes 尔er which is a crossbow. Indeed, crossbows were a primitive machine. The tree radical in Chinese indicates wood but also structured or patterned material objects.
打da3 is hand+peg/nail. The nail here 丁ding1 is a phonetic clue but also semantic: what do you hit? Nails!
火huo3 is a picture of a person’s backside with sexy tatoos. Ok I lied about that one. It’s just a picture of a campfire.

 打火机 da3huo3ji1 lighter.