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  1. #31
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    These are some of the data I got from measuring a Golden Era No. 12. The x axes of the following three plots are in centimeters up from the toothline. The measurement denoted 1 is the measurement 1 cm above the tooth points. The trendlines are cubic polynomial fits done in Excel.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

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  3. #32
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    Thanks for those measurements Rob.

    I think to some extent we are talking about the same thing. If I can return to Gavin's post (#22) where he pointed to a patent on taper rollers. My contention was that Disston did not use the patent to any great extent and that was because the saw plates showed a taper pattern that I felt did not fit with "rolling." Taper grinding usually works in two directions: From the toothline to the back and from Handle to toe along the back of the saw. To my mind it would produce a taper similar to the Simonds pattern I showed in post #24.

    The measurements I took would seem to bear that out: BUT my 1" micrometer will not reach into the middle of the saw plate so I cannot check what is happening there. This is from a Disston publication:

    Disston Taper Saw Grinding..PNG

    These next pix are from a "Disston publication Disston Handbook on saws," which was published over a number of years. I have seen four editions 1902, 1907, 1914 and 1917."

    Disston taper ground in gauge measurements.PNG

    Above is the tapering in gauge thickness of 19 at the toothline and the handle down to 22 at the toe. Below are the grinding machines they used.

    Disston grinding of blades.jpg

    Some of the grinding wheels were large. Not all would have been used on handsaws. Some of the larger wheels might have been for the crosscut logging saws. I recently saw a picture of a crosscut saw that was 20' long: A special order I think . Stock saws up to 8' long were listed in catalogues.


    Disston grinding stones.PNG

    The point I was making was that Disston did not appear to have adopted the use of rolls for tapering their saw plates despite owning the patent. Apart from the patent there is nothing in their literature that suggest they used any other method than grinding wheels.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  4. #33
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    Hi Paul,

    Yes, I think so too about the rolling patents.

    Rolling would be easiest before hardening. It would be quite difficult and time consuming to roll an already hardened blade and not crack or bend it. A blade rolled soft would likely deflect on quenching requiring a lot of hammer work to get it straight again.

    Rolling a hardened blade differentially to taper it would add a gradient of unbalanced internal stresses, more at the thinner back and less toward the teeth. I would imagine that rolling the blades would make them quite difficult to straighten.

    Grinding was (and still is ) done on blades after they were hardened. In fact, hardened blades can be straightened by grinding or by hammer tensioning or both.

    Regards,
    Rob
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  5. #34
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    Here's some data from an Acme 120.

    As you can see, they were hollow ground, but only just. Reality is markedly different from Disston advertising.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  6. #35
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    Default Blade Grind Profiles of three Golden Era Disston No. 77's

    Here are the saws. Two are 12" and one is 8".




    The etches are a little hard to see on the 12" saws but here are some better shots.

    No 77 etch B.jpgNo 77 etch A.jpg


    Here are some graphics depicting the profiles.


    First the 12" saws.
    This is what the 8" saw looks like.



    Now comparing the three saws over the first four centimeters up from the toothline.




    Finally the average deviations for each saw.

    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  7. #36
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    Thanks Rob

    That definitely settles the discussion as to whether the backsaw No.77 was taper ground. You had me going there for a moment as the measurements are metric! I have become so used to talking imperial when discussing saws that it is almost like an alternate dimension (sorry about that one).

    I might have to consider making up a no-set taper ground back saw at some stage. I have a few "replicas" I wish to make and I'll add that one to the list.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  8. #37
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    Um Ye
    What he said [emoji6][emoji3516][emoji3516]

    Cheers Matt.

  9. #38
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    Quote Originally Posted by Bushmiller View Post
    Thanks Rob

    That definitely settles the discussion as to whether the backsaw No.77 was taper ground. You had be going there for a moment as the measurements are metric! I have become so used to talking imperial when discussing saws that it is almost like an alternate dimension (sorry about that one).

    I might have to consider making up a no-set taper ground back saw at some stage. I have a few "replicas" I wish to make and I'll add that one to the list.

    Regards
    Paul
    The grid is metric, the thickness is inch. Growing up in a mixed system I'm kind of ambidextrous. Below you'll see the coordinate system I used.

    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  10. #39
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    Quote Originally Posted by rob streeper View Post
    The grid is metric, the thickness is inch. Growing up in a mixed system I'm kind of ambidextrous. Below you'll see the coordinate system I used.
    Rob

    I understand. I still tend to ask at a timber merchant for a 3m length of 4x2 (or 2x4 ). I have to consciously make myself talk all the same type.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  11. #40
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    This is my deep throat micrometer.



    The burette clamps came from a recent bulk pickup - there were quite a few and a nice electric hotplate on the roadside. The ringstand is another found item, this time from a commercial building clearance.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  12. #41
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    Rob

    That is recycling (or some say repurposing) at it's very best.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  13. #42
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    Default Not done yet...

    Here are three earlier taper ground Disston backsaws.



    The uppermost saw in the picture, made between 1888 and 1896 with a blade length of 16", is the only one that has a legible etch/stamp.

    1888-1896 No 77 etch.jpg

    The second saw from the top with the 12" blade carries an 1878-1888 medallion and the saw at the bottom of the picture with a 10" blade carries an 1871-1875 medallion.

    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  14. #43
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    Rob

    Quite apart from the interesting statistics and incontrovertible evidence that the backsaw blades were indeed tapered, those are three very tidy saws with the oldest in the 150 year old bracket. I think others have commented how backsaws tend to hold up better than handsaws. Posssibly they enjoyed a more gentle lifestyle.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  15. #44
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    Default Did the No. 7 backsaw become the No. 77?

    Here are three earlier taper ground backsaws.




    The upper and lower saws are 1860-1865 production, the middle is an 1865-1871 bearing an '& son' medallion. The saw at the bottom of the frame has an etch or stamp, but it's perpendicular to the toothline and it's clearly a No. 7.



    The other two saws have no visible markings on the plates.



    The early saws weren't ground much, but they were ground.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  16. #45
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    Default Pre-1860 Disston No. 7/77?

    Here's the oldest saw I have of this type.




    No stars adjacent to the wingtips of the eagle.



    As you can see the toothline has drifted up over the years because of sharpening bias toward the toe which complicates my measurements somewhat as the thickest part of the blade is at the toothline at the extreme heel. Nonetheless the measurements still show a taper.



    Thus it seems that Disston was taper grinding saws prior to 1860, but only backsaws. The hand and panel saws were not taper ground until after 1860. Maybe Disston hadn't developed the techniques or machinery to do bigger saws prior to his first saw grinding patent (The history of taper grinding of saw blades, post #3) in June of 1860.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

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