International Workshop Y

Chris' mystery ruler Nr. 9

Drawing ruler with metal strips

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ruler ruler cross section

Data:

  • This is a black coloured timber drawing ruler with at each corner a metal strip, to prevent wear.
  • It is made by Faber Castell and of high quality.
  • At one corner the metal strip is slightly movable.

Questions:

  1. Do you know other manufacturers of drawing rulers who have done similar?
  2. The type of timber is not known. Do you have any idea? Boxwood? Mahogany?
    Probably off-topic, but a comparison of pear and mahogany is given by A. Wasmus (Dennert & Pape?), “Neuerungen am Rechenschieber”, Elektrotechnische Zeitschrift 60(9) (1939-03-02) page 272.
    Wood species Shrinkage or swelling (%)
    due to moisture loss or
    gain between
    0% and 30% moisture content
    (hygroscopic range)    		 Thermal expansion
    (%)
    per 1°C temperature rise
    parall.
    to grain
    αp    		 perp. to grain parall.
    to grain
    αp    		 perp.
    to grain
    αs
    αs rad. αs tang.
    Pear
    (Pyrus communis)    		 0.4 4.6 9.1 0.0006 0.005
    Mahogany
    (Swietenia mahagoni)    		 0.3 3.2 5.1 0.0004 0.004
    Andries de Man