Screws are used to fasten hinges and bolts on doors and shutters, and to fasten pieces of wood together in the construction of houses, boats, wagons, and other things.
For what other purposes is the screw used?
The screw is used where much power is needed, as in the vise; where pressure is desired, as in copying letters, and in coining money; and, also, for squeezing the juice from apples, grapes, and sugar-cane.
Fig. 61.
In what does a screw like that in [Fig. 61] work?
It works in a nut which has threads cut on the inside, so that the threads of the screw move in them.
Where is the power applied?
The power is applied to the lever.
Can heavy bodies be raised by means of this screw?