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  1. #1
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    Default Analysis of Disston Acme 120 Saws

    Yet another chapter of my investigations of Disston production methods and products.

    These saws were produced for the trade over a span of about 30 years from the late 1880's to the mid 1920's. They were taper ground in such a way as to obviate the need for setting the teeth. They were also reputed to be especially hard. The later of these saws is harder (HRC= 57) than the average Disston saw and the earlier is not.

    This is the earlier saw (1888-1896).




    And this is the later (1896-1917).




    Both have visible etches.




    I laid out a 1 cm. X 3 cm. grid on both blades like so,




    and measured the thickness profiles of the saws.

    Here is the color code key.



    This is the profile of the early saw.


    This is the profile of the later saw.

    As you can see the later, harder and smaller saw is more heavily tapered than is the earlier saw.

    Leaving aside for a moment the most heavily thinned areas on the very toe and the edge of the back it's apparent that the early saw is effectively ~0.0125" thinner toward the back than it is at the toothline and the later saw is ~0.0165" thinner. Both saws taper 0.003"-0.005" in the first centimeter up from the toothline and both have a very slight hollow grind in the area near the top front of the handle suggesting the use of a grinding wheel of 6-8 cm. width.
    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. #2
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    So which way is the blade oriented to the wheel?

  4. #3
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    From these data and the video discussed in the taper grinding thread I'm pretty sure that they were ground from toe to heel and that the wheel was rotating in the same direction.
    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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    I wonder if the wheels had a slight crown on them to enable the hollow grind and to prevent grooving from the corner?

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    Could be. I'm also planning to measure some saws that are contemporaries of the two Acme's, I suspect that some, like the No. 12's, aren't much different in profile.
    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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    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  8. #7
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    Numeric data


    All of the Acme 120's are significantly different statistically from their period peers but only the Golden Era saw is different enough to really matter. Probably explains why some of the No. 77's have been set.
    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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    Another Acme 120 added to the data. This one is a 1918-1928 date saw. It's also soft, softer than the other from this period.
    Innovations are those useful things that, by dint of chance, manage to survive the stupidity and destructive tendencies inherent in human nature.

  10. #9
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    Here are displayed data for yet another Acme 120 and a No. 77 backsaw.



    As you can see, in the 19th century the 'specials' were all a little harder than the average saw of their respective production periods. During the 1896-1917 medallion period one Acme 120 had a blade that was sigificantly, statistically and functionally, harder than average. The No. 77 backsaw (blue bar) was a little softer than average. Post 1917 the wheels fell off and the specials in my collection are softer than average.

    Here are the numeric data.

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

  11. #10
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    I found this for sale recently and thought it would be a good addition to my study of Disston's (supposedly) extra hard saws. I was unaware that the Acme 120 line extended to scrapers. The saws were discontinued in the late '20's.

    Acme 120 scraper 002.jpgAcme 120 scraper 001.jpg

    The look and feel of the engraving is very much like that of laser engraving but I don't think that the technology was available commercially until the '70's. Under a 5X hand lens the letters look like they were made by a dot-matrix printer. It's 0.035" thick and measures 2.935" X 4.826".

    Expecting to see exceptional hardness I tested it and found that it's HRC 50.3. Nothing but plain old saw steel. Disston (the company) did a lot of lying it seems.

    Here's the data with those of the saws.




    Or, to be charitable, it's a 7/8 lie.
    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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    Found an Acme 120 Cabinet Scaper advertised here: https://books.google.com.au/books?id...craper&f=false

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    Cool, thanks. Here's the page clipping.
    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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    Thanks. I really like the heat-map idea.

    Of course it's your prerogative ... would you mind posting those two sets of values for me/us to have a look at?

    I'd be happy to add to the "database" ... but it wouldn't happen soon, unfortunately. (More like - in the back of my head over the next year. )

    Thanks,
    Paul.

  15. #14
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    Quote Originally Posted by pmcgee View Post
    Thanks. I really like the heat-map idea.

    Of course it's your prerogative ... would you mind posting those two sets of values for me/us to have a look at?

    I'd be happy to add to the "database" ... but it wouldn't happen soon, unfortunately. (More like - in the back of my head over the next year. )

    Thanks,
    Paul.
    Here are the raw data on the same maps.

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

  16. #15
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    Here's the thickness profiles of all five Acme 120 handsaws in my collection.

    First are the two saws dating from 1880-1896.




    This is the single Golden Era saw.


    Finally the two saws dating from 1918-1928.



    As you can see, the Golden Era saw is the most deeply ground. The 1880-1896 saws aren't much thicker. The 1918-1928 saws however show a clear reduction in the depth of grinding.
    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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