Editing Slide rule (section)

===Materials===
Traditionally slide rules were made out of a relatively dense, stable hardwood such as [[mahogany]] or [[boxwood]] with cursors of glass and metal. Aluminum was used, and at least one high precision instrument was made of steel.

In 1895, a Japanese firm, Hemmi, started to make slide rules from [[celluloid]]-clad bamboo, which had the advantages of being dimensionally stable, strong, and naturally self-lubricating. These bamboo slide rules were introduced in Sweden in September, 1933,<ref>{{cite web|url=https://runeberg.org/tektid/1933a/0348.html|title=336 (Teknisk Tidskrift / 1933. Allmänna avdelningen)|publisher=Runeberg.org|access-date=2010-02-20}}</ref> and probably only a little earlier in Germany.

Scales were also made of celluloid or other polymers, or printed on aluminium. Later cursors were molded from [[acrylyl group|acrylics]] or [[polycarbonate]], sometimes with [[polytetrafluoroethylene|Teflon]] bearing surfaces. 

All premium slide rules had numbers and scales deeply engraved, and then filled with paint or other [[resin]]. Painted or imprinted slide rules were viewed as inferior, because the markings could wear off or be chemically damaged. Nevertheless, Pickett & Eckel, an American slide rule company, made only printed scale rules.{{cn|date=March 2025}} Premium slide rules included clever mechanical catches so the rule would not fall apart by accident, and bumpers to protect the scales and cursor from rubbing on tabletops.