# screwback
## English
### Etymology

From screw +‎ back.

### Noun

screwback (uncountable)
* The period of screw rotation during injection molding when the plastic can flow into the mold.
** 1978, Society of Plastics Engineers Annual Technical Conference, page 72:Two main phenomena have been emphasized: (a) The transient nature of plastication during periods of screw rotation ("screwback") in comparison with the similar process in continuous extrusion. (b) The significant amount of melting produced by thermal conduction from the barrel while the screw is not turning.
** 1980, Modern Plastics Encyclopedia, page 319:But in the open (screwback) position, the plastic must progress through a series of labyrinths which produces a more turbulent flow.
** 2013, A.A. Collyer, A Practical Guide to the Selection of High-Temperature Engineering., →ISBN, page 45:Screwback time is a limiting factor when the plastication rate of the machine is too small or if the cooling time is small, as is the case with thin-walled mouldings.
* A hook-shapped attachment for an earring that sits behind the earlobe and tightens with a screw. Also, an earring that uses this type of attachment.
** 2007, Rayner W. Hesse, Jewelrymaking Through History: An Encyclopedia, →ISBN, page 93:The clip was a variation of the screwback; today, many persons who cannot wear pierced earrings choose clips as an option.
* A mechanism for attaching a small item to clothing that operates by a post which goes through the cloth and a small backing plate that screws to the post. Also, the medal, tie pin, button, etc. that uses this type of attachment.
** 1921, The Bricklayer, Mason and Plasterer - Volumes 24-25, page 262:The quality of these buttons and charms is best rolled gold and hard enameled in correct colors, the button having either a screwback or a jewelers' catchpin.
** 2012, Henry Sakaida, Heroines of the Soviet Union 1941-45, →ISBN, page 59:The medal screwpost is placed through the uniform and retained by a circular screwback plate.
* A type of case for a pocket watch where the mechanism is accessed by a removable back plate that screws onto the back of the case. Also, a watch that has such a case.
** 2013, John Paul Catton, Time Hunter: Kitsune, →ISBN:The watch stolen from Dan Payton had been an Elgin, with a screwback military case.
* (snooker, pool, billiards) The effect of putting backspin on the cue ball.
* (golf) A powerful shot that imparts a spin to the ball.
** 2014, Margaret Irwin, These Mortals, →ISBN:There he was three into the bunker and bogey for the hole was four, and making up his mind to lay the ball dead, he took his niblick and executed a beautiful screwback shot which landed within a foot of the pin, rolled to the edge of the hole, and there stopped dead, doubtless owing to the eternally damned influence of the aforesaid cloven hoofprint.
* (ping-pong) A half-volley executed by holding the racket loosely and swinging it straight at the ball.
* (architecture) A masonry abutment on an arch that is wedge-shaped in order to transmit the thrust downward.
** 1941, Association of Ontario Land Surveyors, Annual Report, page 72:The main arch abutments are 25 feet wide by 75 feet long and approximately 60 feet deep from the top of the screwback to the bottom of the footings.
* An industrial digging machine that uses a large screw at the back to drill into the ground.
** 1968, Civic Administration - Volume 20, page 61:With the help of a screwback shovel, it was excavated to a depth of 13 ft.
* A type of propeller in which the blades are angled to produce a motion similar to threading a screw. Also, the angle of the blades on such a propeller.
** 1983, Fairplay International Shipping Weekly - Volume 286, page 39:The new propeller which was installed in 1982 was a screwback type with a diameter of 5,500 mm. and a mean pitch of 4,290 mm.
* A tightening screw on the back of a hand tool.
** 1931, Motor - Volume 55, page 91:Ball Bearing armature and spindle thrust, three jaw screwback chuck.

#### Synonyms

* (effect of putting backspin on the cue ball): backspin, screw
* (masonry abutment): skewback