Casting is the process of production of objects by pouring molten material in to a cavity called a mould and allowing it to cool and solidify. Sand casting is a means of producing rough metal castings using a mould usually made from sand formed around a replica of the object to be cast that is removed once the sand has been compacted.
Castings made by this process can be further refined by machining.
From the design, provided by an engineer or designer, a skilled patternmaker builds
a pattern of the object to be produced, using wood, metal, or plastic. The metal
to be cast will contract during solidification, and this may be non-
Paths for the entrance of metal, during the pouring (casting) process into the mould cavity are called 'runners'. Gas and steam generated during casting exit through the permeable sand or via the riser, are added either in the pattern itself, or as separate pieces.
A multi-
The box containing the sand mold is then positioned for filling with molten metal—typically iron, steel, bronze, brass, aluminum or magnesium alloys. After filling with liquid metal the box is set aside until the metal is sufficiently cool to be strong. The sand is then removed revealing a rough casting that, in the case of iron or steel, may still be glowing red.
To harden by quenching, a metal (usually steel or cast iron) must be heated and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done in oil, , water, or brine.
Quenched steel, while very hard and strong, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. For most steels, tempering involves heating, then cooling slowly over an appropriate length of time (minutes or hours). This heat treatment results in higher toughness and ductility, without sacrificing all of the hardness and tensile strength gained from rapid quenching.
Annealing is a process of heating and maintaining at a suitable temperature, and then cooling very slowly. It is usedafter hardening and tempering to induce softness, relieve internal stresses, refine the structure and improve cold working properties.
Hardening
Tempering
Annealing
A metalwork lathe is a machine tool designed to remove material from a work piece, through the action of a cutting tool. They were originally designed to machine metals; however, with the advent of plastics and other materials, they are used in a wide range of applications, and a broad range of materials. They are the most versatile of machine tools and come in all sizes. They can machine components as small as watch parts or jewellery to the longest of ship drive shafts.
Construction (Select graphic above )
These machines consist of, a headstock, bed, carriage and tailstock. These machines are solidly constructed and manufactured with great precision. This helps ensure the components manufactured on the machines can meet the required tolerances and repeatability.
Headstock
The headstock houses the main spindle and the speed change mechanism. The headstock is required to be made as robust as possible. The main spindle is generally hollow to allow long bars to extend through to the work area. The spindle then runs in precision bearings and is fitted with a chuck to hold work.
Carriage
The carriage holds the tool bit and moves it longitudinally (turning) or perpendicularly (facing) under the control of the operator. The operator can move the carriage manually via the handwheel
The cross-
The cross-
Compound slide
The Compound slide is the part of the machine where the tool post is mounted. It provides a smaller amount of movement along its axis via another leadscrew. It is used when turning tapers.
Toolpost
(1) The tool bit is mounted in the toolpost
Tailstock
The tailstock is a toolholder directly mounted on the spindle axis, opposite the headstock. The spindle does not rotate but does travel up and down the slides. The spindle includes a taper to hold drill bits, centers centre drills and twist drills. The tailstock can be positioned along the bed and clamped in position as required. With a centre fitted the tailstock can be used to support and steady longer work such as hammer handles.
Setting of a Cutting Tool on a Metalwork Lathe
When facing off, if the tool point
is higher than the centre of material, the tool point does not touch the material,
and the tool cannot cut at all. Conversely, if the tool point is low, it becomes
impossible to cut the center of material and a ‘pop’ is left
. (See below)
Metalwork Lathe
Heat treatment
