Rolling mills was said to be one of the tools that a jewelers must have. It is a tool that is used to make a sheet or wire from a scrap of gold. It is being used to apply pressure to a metal to flatten it and to make it longer.
A rolling mill, also known as a reduction mill or mill, has a common construction independent of the specific type of rolling being performed:
- Work rolls
- Backup rolls - are intended to provide rigid support required by the working rolls to prevent bending under the rolling load
- Rolling balance system - to ensure that the upper work and back up rolls are maintain in proper position relative to lower rolls
- Roll changing devices - use of an overhead crane and a unit designed to attach to the neck of the roll to be removed from or inserted into the mill.
- Mill protection devices - to ensure that forces applied to the backup roll chocks are not of such a magnitude to fracture the roll necks or damage the mill housing
- Roll cooling and lubrication systems
- Pinions - gears to divide power between the two spindles, rotating them at the same speed but in different directions
- Gearing - to establish desired rolling speed
- Drive motors - rolling narrow foil product to thousands of horsepower
- Electrical controls - constant and variable voltages applied to the motors
- Coilers and uncoilers - to unroll and roll up coils of metal
Slabs are the feed material for hot strip mills or plate mills and blooms are rolled to billets in a billet mill or large sections in astructural mill. The output from a strip mill is coiled and, subsequently, used as the feed for a cold rolling mill or used directly by fabricators. Billets, for re-rolling, are subsequently rolled in either a merchant, bar or rod mill. Merchant or bar mills produce a variety of shaped products such as angles, channels, beams, rounds (long or coiled) and hexagons.
Before using the rolling mill, anneal the metal you'll be working with. Annealing is basically the heating and then cooling (the speed of cooling depends on the metal you're working with; some need to sit until cool, some may be quenched with water or other solutions) of a piece of metal to improve its toughness and to eliminate its potential brittleness. Before working with your metal, make sure that it is clean of contaminants. This can be done by pickling your metal using an acidic solution (which is often heated), neutralizing the acid by dipping the metal in a base solution and then rinsing it in clean water and drying it. Try to keep the oils from your hands off your metal as much as possible as this can cause tiny pits to form.
Place the end of your metal piece into the machine (as close to the middle of the rollers as possible so that the pressure will be even) and tighten the mill down until the rollers are snug (but not tight) on the piece. It should be fairly easy to move the crank. If it is very difficult to roll your piece through, the rollers need to be loosened or you will risk damage to both them and your piece.
