Spin Forming Forming with an English Wheel Piccolo Former In spin forming, a flat circle of metal is rotated at a very high  speed to shape a seamless, hollow part using the combined  forces of rotation and pressure. For example, a flat circular  blank such as an aluminum disk, is mounted in a lathe in  conjunction with a form block (usually made of hardwood).  As the aircraft technician revolves the disc and form block  together at high speeds, the disk is molded to the form  block by applying pressure with a spinning stick or tool. It  provides an economical alternative to stamping, casting, and  many other metal forming processes. Propeller spinners are  sometimes fabricated with this technique. Aluminum soap, tallow, or ordinary soap can be used as a  lubricant. The best adapted materials for spinning are the  softer aluminum alloys, but other alloys can be used if the  shape to be spun is not excessively deep or if the spinning  is done in stages utilizing intermediate annealing to remove  the effect of strain hardening that results from the spinning  operation. Hot forming is used in some instances when  spinning thicker and harder alloys.  [Figure 4-63] The English wheel, a popular type of metal forming tool  used to create double curves in metal, has two steel wheels  between which metal is formed.  [Figure 4-64]  Keep in mind  that the English wheel is primarily a stretching machine, so  it stretches and thins the metal before forming it into the  desired shape. Thus, the operator must be careful not to  over-stretch the metal.  To use the English wheel, place a piece of sheet metal  between the wheels (one above and one below the metal).  Then, roll the wheels against one another under a pre-adjusted  pressure setting. Steel or aluminum can be shaped by pushing  the metal back and forth between the wheels. Very little  pressure is needed to shape the panel, which is stretched or  raised to the desired shape. It is important to work slowly and  gradually curve the metal into the desired shape. Monitor the  curvature with frequent references to the template. The English wheel is used for shaping low crowns on large  panels and polishing or planishing (to smooth the surface of a  metal by rolling or hammering it) parts that have been formed  with power hammers or hammer and shot bag. The Piccolo former is used for cold forming and rolling sheet  metal and other profile sections (extrusions).  [Figure 4-65]  The  position of the ram is adjustable in height by means of either a  handwheel or a foot pedal that permits control of the working  Figure 4-64.  English wheel. Figure 4-63.  Spin forming. Figure 4-65.  Piccolo former. 4-26