laboratory or dispensing scale

dosing scale from England

This scale comes from England. I found an image of this scale in old catalogs of two English firms. The one image at Griffin & Tatlock from the 1930s. The other image at W. & J. George & F.E. Becker from 1939. It is a laboratory or dosing scale for accurately weighing powders. My copy was incomplete: the tray, the bracket and the suspension were missing. I made those parts to make the scale complete again. My detachable dish is made of brass instead of glass. The weighing range is from 0 - 8 drachms subdivided per ½ drachm and from 0 - 30 grains subdivided per ½ grain. 8 drachm = 1 troy ounce = 60 grains, 30 grains = 1,5 scruple = 0,5 drachm, 1 grain = 1/480 ounce = 31,1/480 = 64,8 mg or 0,0648 grams, and ½ grain = 32,4 mg = 0,0324 grams. 1 troy ounce = 31,1034768 grams.

back of the dispensing scale

The scale mechanism design here is largely a copy of dispensing scale designed by Fairbanks in America. This Fairbanks dispensing scale is described in patent US202800 dated April 23, 1878. A slightly modified Fairbanks dispensing scale was issued on August 20, 1878, patent US207263. A subsequent design for a Fairbanks dispensing scale was repeatedly rejected in England in 1905 and therefore not approved as a prescription or dispensing scale. This information is taken from an article in Equilibrium No.1 1991, pp1422-1425 by R. Grice with the title: Avery? Fairbanks?. To illustrate the similarities, at the bottom of this web page are the images of the US patents, the Fairbanks prescription or dosing scale, the Avery laboratory scale, and the dispensing scale by an unknown maker shown here.
Below some more pictures of the English dispensing scale of which I do not know the brand for sure.

animation: the tray can be detached [move the pointer over the photo]

animation: the tray creates a balance [move the pointer over the photo]

animation: the knife edge bearing for the bracket and the tray [move the pointer over the photo]

the knife edge bearing	top view	back of the fine adjustment
movable weight on the scale up to 8 Drachms	the scale up to 30 Grains	the movable light weight on the Grains part
Drachms per ½ drachm	Grains per ½ grain	the bottom of the frame base
at equilibrium the parts are in line	front of the fine adjustment	in balance, the point almost touches the bend

prescription scale from the 1902 Fairbanks catalog

drawing from patent US202280 of April 23, 1878

drawing from patent US207263 of August 20, 1878

from the 1916 Avery catalog, this figure is also in the 1909 Avery catalog

Fairbanks prescription scale 1902 source: Equilibrium 1978, pp74

the disapproved Fairbanks September 1905 Source: Equilibrium 1991, pp1423

the disapproved Fairbanks December 1905 source: Equilibrium 1991, pp1425

from a catalog of Griffin & Tatlock 1930s

the accompanying text from that catalog of Griffin & Tatlock 1930s

from a 1939 catalog of W. & J. George & F.E. Becker