Question

Suppose a conventional water bottle cap is made with a single-start thread of 0.125 in pitch. Further suppose that the lid must be rotated 2.75 times to com- pletely close the bottle, requiring the typical use to re-clutch the lid approximately 4 times to screw the lid shut. If the lid is re-designed with exactly the same pitch, but three starts, rather than one, how many times must the lid be rotated to completely close the bottle?

Answer 1

11/12 Rev is required to completely close the bottle

Step-by-step explanation:

Given the data in the question;

pitch = lead = 0.125 inch

total distance moved in 2.75 rotation = 0.125 in × 2.75

Now; Redesigned thread is three (3) start

lead = 3 × pitch = 3 × 0.125 inch

so

Number of turns required = total distance moved / distance moved in one rotation

Number of turns required = total distance / lead

we substitute

Number of turns required = 0.125 in × 2.75 / 3 × 0.125 inch

= 2.75 / 3

= 275 / 300

reduce the numbers ( by dividing the numerator and denominator by 25 )

Number of turns required = 11/12 Rev

Therefore, 11/12 Rev is required to completely close the bottle