lower leaf

master leaf

upper leaf

none of these

1 in l5 to 1 in 10

1 in 24 to 1 in 20

1 in 32 to 1 in 24

1 in 48 to 1 in 24

Acme threads

Square threads

Buttress threads

Multiple threads

5 times

10 times

15 times

20 times

small overall dimensions

accuracy of shaft alignment

low starting and low running friction except at very high speeds

all of the above