Dental metallurgy; a manual for students and dentists.

  • Arthur Bower Griffiths
Date:
1903
Catalogue details

Licence: In copyright

Credit: Dental metallurgy; a manual for students and dentists. Source: Wellcome Collection.

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    most cases the wire is annealed from time to time in order to prevent undue hardness; in some cases, however, annealing is omitted (hard-drawn wire). Fig. 3.—Draw-Plate. 3. Brittleness.—A metal is said to be brittle when it breaks readily under a blow (e.g. bismuth and antimony); but some brittle metals become malleable when heated {e.g. zinc), and some malleable metals become brittle when heated. This is an important point in the preparation of dies and counter-dies. 4. Elasticity.—A metal is said to be elastic when, after stretching or bending, it tends to return to its original form {e.g. steel). Elasticity varies in different metals, and is utilised in matrices, clasps, etc. Wire-drawing, rolling, and hammering increase the elasticity of metals, while annealing generally diminishes it. “ Limit of elasticity ” is the point at which metals are incapable of regaining their original form. Adhesion is the force of attraction exerted between the particles of different metals. It is an important projierty, but requires further investigation. It may play an important part in alloys and amalgams. The union of metals by solders is due to adhesion. Tenacity.—A metal is said to be tenacious when it possesses the property of resisting fracture when subjected to a tensile or pulling force. The tenacity is tested liy taking wires of the same diameter, fixing them at one end and suspending weiglits at the other, and then noting tlie greatest weight each wire is capable of supporting without breaking. Steel is the most and lead the least tenacious of