Birmingham Gage Table

Discussion in 'Saw Pictures and Measurements' started by ray, Aug 24, 2008.

  1. ray

    ray Guest

    Conversion table, to convert Saw Plate thicknesses to thousanths of inch

  2. shoarthing

    shoarthing Most Valued Member

    Thank you - tho' to me this remains a puzzle-area, despite fairly recent published research. Charles Holtzappfel in the second volume of Turning and Mechanical Manipulation (1847 - but took decades to write, so some info outdated on publication) gives a well-known table of gages for backsaws:
    Screenshot 2021-04-30 at 10.30.01.png
    . . . which would seem to settle the measure as "Birmingham Wire Gage" . . . but a table in Velkar's: Emergence of the British Standard Wire Gauge (2007), derived from Thomas Hughes' The English Wire Gauge (1879), might infer a closer relationship to the Manchester Wire Gauge:
    Screenshot 2021-04-30 at 10.39.26.png
    . . . given that 10" dovetail saws of this sort of era, if toothed in the ppi range of 14-18, were generally constructed of 20 thou plate.

    But alas this happy agreement of 20 thou/24 MWG is singular, immediately made uncomfortable by the huge jump between 23 MWG ((roughly) 22 thou), and 22 MWG (30 thou); whereas 11 ppi 14" Sash Saws of this era are as a generality found to be plated at 25 thou.

    . . . . to which which none of the above scales agree.

    Happy are we to live in an age of few Standards.

    Attached Files:

  3. ray

    ray Administrator Staff Member

    Thanks for that update. I think my conversions obviously went awry somewhere along the line. I was under the impression that earlier small dovetail saws were more like 15 thou to 18 thou.

    shoarthing likes this.
  4. shoarthing

    shoarthing Most Valued Member

    Hi - indeed many were. The hassle with gage tables is there were so many local ones, changing - wearing with their prime draw-plates - through the decades. Holtzappfel was as you know - alongside Stubs - a strong advocate of absolute gauges relative to thou; but his above table of backsaw properties - alongside gage - appear far away from actual practice.

    Edit: for an actual saw-maker’s plate-thickness gauge, made by STUBS/Sanderson Bros. & Newbould, see this post
    Last edited: Jan 20, 2022