Abstract: A rotary hook for a sewing machine has a rotatable hook drive shaft driving a hook body in cooperation with a reciprocating needle which moves toward and away from the rotary hook. The hook body has a revolving rotary hook tip which is movable in a path relative to the needle and is engageable with the thread presented by the needle. The rotary hook includes a thread deflecting shoulder to enlarge the thread to form a needle thread loop, includes a case holder having an annular guide rib and a pin extending axially outwardly of the holder. A bobbin case has a central hollow sleeve into which the pin extends and a latch engageable with the pin to hold the case holder to the bobbin case. The case each holder and the bobbin case have a sidewall with interiors which are in substantial alignment. The bobbin case holder has a rearwall formed as a substantially truncated cone which is eccentric to the guide rib and the bobbin case has an annular sidewall and a frontwall have an arched mushroom shape.