Sheaffer used a dial indicator nib gauge for measuring nib sizes. The nib was inserted into the gauge, and the size read off of the dial. A given size being nibs that fell within a given range. What is listed below were the ranges given on a gauge that I saw in the Sheaffer service center prior to being closed in March 2008.
Measurements are in thousandths of an inch.
XXF = 0.010 - 0.013
XF = 0.013 - 0.018
F = 0.018 - 0.025
M = 0.025 - 0.031
Broad* = 0.031 - 0.050
Stub = 0.038 - 0.050
*there was some overlap on the gauge. May be 0.035 - 0.050
Edited by Ron Z, 07 October 2009 - 15:40.
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