Planishing

Planishing (from the Latin planus, "flat")[1] is a metalworking technique that involves finishing the surface by finely shaping and smoothing sheet metal.

Diagram of planishing, showing planishing hammer, workpiece, and planishing stake (hammer not to scale)

Process

This is done by hammering with a planishing panel hammer or slapper file against a shaped surface called a planishing stake that is held in a vise or a mounting hole in a blacksmith's beak anvil,[2] or against hand-held, shaped, metal tools that are known as Dollies or Anvils. The shape of the stake or dolly has to match the desired work piece contour, and so they come in a variety of complex shapes. Alternatively, planishing may be done by the use of an English wheel. After approximately forming a metal object, by stretching with techniques such as sinking and raising, and then shaping and smoothing an object, metal workers use planishing for surface finishing. Planishing is a hand-driven process used in auto body repair and sheet metal craft work such as medieval armour production.

Tools

Common tools used for planishing include panel beating hammers, slappers, and neck hammers.[3] Heavy rawhide or hardwood hammers are often used. It is more difficult to make mistakes with heavy rawhide or wood mallets, but they are less effective for large imperfections.[4] A worker, using repeated, relatively soft glancing blows, smooths the metal toward the curvature of the stake. If the metal begins to look dimpled, the worker is using too much force in individual hammer blows.[4]

Features

Since planishing hammers are generally in contact with the outside surface of the piece, they are flat, have rounded edges and are polished to avoid marring the work.[5] Pneumatic (air powered) planishing hammers strike hundreds of blows per minute.[6]

Care must be taken not to allow sheet metal to harden and become brittle during planishing. If it does, it must be annealed.

References
  1. McCreight, Tim (1991). The Complete Metalsmith. Worcester, Massachusetts: Davis Publications. p. 61. ISBN 0-87192-240-1.
  2. Price 2000, p. 179.
  3. Payne, Arthur F. (2003). Art Metalwork with Inexpensive Equipment. Gustav's Library. p. 64. ISBN 0-9758914-2-1.
  4. Dettelmach, Gundobad von (January 13, 2009). "Planishing".
  5. Price 2000, p. 79.
  6. Air Planishing Hammers, Grainger, lists hammers available with 1800 to 5400 Blows per Minute, accessed 10 June 2020.

Bibliography
  • Yule, Paul (1988). "A Harappan 'Snarling Iron' from Chanhu daro, Antiquity 62, 116-118". Antiquity : A Review of World Archaeology. Durham, U.K.: Durham University. ISSN 1745-1744.
  • Price, Brian (2000). Techniques of Medieval Armour Reproduction. Boulder, Colorado: Paladin Press. ISBN 1-58160-098-4.
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