Carcase or sash?

Discussion in 'Forum: Saw Identification and Discussion' started by shoarthing, Sep 14, 2020.

  1. shoarthing

    shoarthing Member

    Messages:
    5
    A plea for help to those assembled herein: I would very much like to know what this de-handled carcase of a saw looked like when new-made. It has been treated unkindly; not by me.

    Material & condition:

    I believe the 13 ½" sawplate to be original; it was made of 20-thou stuff, & is toothed at 11 tpi. It is plurally buckled & re-buckled at the toothline, tho' firmly & straightly clasped by the back.

    The 13 ½" brass back tapers evenly in height by ¼" . . . . from 7/8" to 5/8". It is folded/formed from 1/8" stuff & is noticeably wedge-shaped in cross-section; emphasised by its lower edge being chamfered, then (outside the mortice) rounded. It tapers slightly - by a trifle over 1/32" - in breadth, back to nose. The nose is closed.

    Geometry:

    291305A4-D629-434A-9F56-853A85FD2ADB.jpeg

    In the large image the saw is laid out on an annotated board, sawplate between two vertical lines 13 ½" apart. With the nose of the sawplate vertical, the back & back of the sawplate are approx. aligned together & raked forward at approx. 5°

    The original cant appears to be around ¼"

    (ghost) Handle:

    The original handle was fixed through the 2x larger, worn, & roughly vertical holes. A non-fitted replacement handle was fixed through the two smaller & roughly horizontal holes - those latter fixings were factory-made ½" flat saw-screws.

    A ghost outline on the sawplate - vaguer at the bottom due to the handle shifting approx 1/8" down as the holes ovalised - suggests a compact, plump boss, with an accelerating upward curve towards the back of the plate. Tho' less reliable an indicator; patina/dirt to the back suggests it was fitted full-depth into its original mortice.

    D49C4D76-AE41-4876-BBB7-511BC7A01F98.jpeg


    Pleas:

    What examples (other than the lovely Howel in this thread) can you recall of the back edge of a sawplate & its back together raked forwards by 5° or so?

    C8D391E2-DB50-42DA-911E-053192FEFD15.jpeg

    What examples can you recall of brass backs tapered both in height & (very slightly) in breadth . . . and with a rounded lower edge . . . . and with a closed nose?

    What examples can you recall of brass backs so wedge-shaped in cross-section?

    D943A3FD-2832-42E8-85EC-E60236EE7990.jpeg

    What examples of canted sash saws do you know of with plates originally formed of 20-thou stuff?

    NB: of modern makers of folded-back backsaws - stresses are different for slot-and-epoxy construction - all (but Gramercy) appear loathe to offer 20-thou sawplates with cutting-depths at the nose greater than around 2 ¼", or toothings coarser than around 13 tpi.

    . . . . and the Big One: what form - probably - was the handle?

    PS: thank you in advance . . . . if I have observations on the remains of this saw (I have been a cabinetmaker since the 1970s, and have a degree & so on in Archaeology), they are that it took an exhibition of craft to make; yet was functionally duff. Given the qualities of its steel, the plate was too thin for its toothing & depth. I will admit - on finding this saw - to being overcome with hazy Smith's Key curliques.
     
    Last edited: Sep 14, 2020
  2. David

    David Most Valued Member

    Messages:
    285
    Here's one example by Rutter, although Cast Steel rather than London. At least it shows the form of one handle he made. I hope this helps you.
    David
    Rutter.jpeg
     
  3. shoarthing

    shoarthing Member

    Messages:
    5
    David - Hi - thank you.

    So many Rutters . . . . . that's a really nice saw.

    (EDIT) the more I look at your sash saw; the closer it feels in style & presumably time to mine & its conjectural handle. Thank you for this exemplar of Rutter-ness.

    May I ask how thick the handle is to allow such generous chamfers?
     
    Last edited: Sep 17, 2020
  4. Dusty Shed Dweller

    Dusty Shed Dweller Most Valued Member

    Messages:
    120
    Many questions.

    I'll start with easy ones. Plate thickness and depth.

    When building a saw, deeper plates are harder in the first place to make plumb, keep in tension and straight, and require a perfectly manufactured spine. In addition, deeper plates and lightly set saws heat up with cutting, expand, lose tension and don't track properly, hence the proclivity to keep the plates as shallow as possible to help keep the plate in tension and tracking true. Also, the maximum depth of cut of a backsaw is half the plate height. Anything else is saw abuse. Sink it to the spine and you'll wreck it sooner or later.

    Toothing is controlled by the physical constraints on tooth height versus width. Too small and they become stubbier than the spacing, they clog with saw dust and cut poorly. Too big and the lateral forces overwhelm the strength and promotes kinking. Notwithstanding finagling rake angles etc, for a 20 thou 1075 spring plate the practical Toothing range is 12-18 ppi, although you'd want a relaxed rake at the coarser end and an aggressive rake at the fine end. I'd use a 3 square to get the gullets as deep as possible at the fine end as well, as the gullets shift the swarf.

    We build saws with a forward rake on the front edge so the saws cut all the way to the tip and aren't stymied by the tip of the spine. If you've ever fitted trim etc you'll understand why.
     
  5. shoarthing

    shoarthing Member

    Messages:
    5
    Thank you - that's an interesting observation.
     
    Last edited: Sep 15, 2020