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


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  2. shoarthing

    shoarthing Member

    Messages:
    18
    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Holtzappfel in the second volume of Turning and Mechanical Manipulation (1847 - but took decades to write, so some info outdated on publication) gives a well-known table of gages for backsaws: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.
     

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  3. ray

    ray Administrator Staff Member

    Messages:
    659
    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.

    Regards
    Ray
     
    shoarthing likes this.
  4. shoarthing

    shoarthing Member

    Messages:
    18
    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.