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  1. 25th January 2014, 01:57 PM #1
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    pmcgee
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    Default Manual Training for Common Schools - 1910

    I'm not sure that I have seen this before, but I came across it last night.

    It is downloadable - and looking at it as still quite a beginner - I think it is bloody awesome!

    https://archive.org/details/cu31924003595364

    One little thing that piqued my interest in particular ... regarding sawing technique ...

    It only mentions drawing back the saw to help start the cut in regard to crosscut saws.

    That makes sense, because crosscut teeth are shaped to cut in both directions ... even though the effective rakes will be different.

    Cheers,
    Paul

    In fact ... 'neutral' in a sense for xcut teeth would be 30o rake ... making the teeth identical little upright equilateral triangles.
    In that shape the forward stroke rake = the back stroke rake = 30o.

    With the normal xcut rake less than 30o, then the backwards motion will effectively be cutting with a rake of greater than 30o, which should be an easier but slower cutting effect than on the forward stroke.
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  3. 25th January 2014, 03:01 PM #2
    Heavansabove
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    Quote Originally Posted by pmcgee View Post
    That makes sense, because crosscut teeth are shaped to cut in both directions ... even though the effective rakes will be different.
    Paul, can you please clarify by what you mean by crosscut teeth?

    Cheers
    Peter
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  4. 25th January 2014, 06:24 PM #3
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    Quote Originally Posted by Heavansabove View Post
    Paul, can you please clarify by what you mean by crosscut teeth?
    Cheers
    Peter
    I mean like your normal 'across the grain' saw ... like in this US War Dept manual (http://www.ibiblio.org/hyperwar/USA/...fs/TM9-867.pdf)

    (not the huge tree-cutting saws)

    Cheers,
    Paul

    War Dept - saws.JPG
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  5. 25th January 2014, 06:50 PM #4
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    I should have picked this picture instead ...

    crossprofile2.JPG

    Those saw teeth would be intended to cut travelling to the left, but there are bevels all around so it could also do sorta the same job cutting to the right.

    - - -

    But thinking a bit more about it, regarding pulling back to start, there are two differences ... the rake will be different (greater) unless the teeth are equilateral triangles ... but also the forces applied will be like the difference between pushing a wheelbarrow and pulling a wheelbarrow.

    Applying a forward effort to a wheelbarrow equals trying to move the front wheel forward and down.
    Pulling the wheelbarrow acts on the wheel backward and up.

    So in effect it's also an (unconscious) way of lifting the weight of the saw out of the cut.
    I've been starting cuts only forward for a good long time, being schooled by Chippy and IanW ... but it does need a very conscious lifting of the weight of the saw in starting. (I'm talking handsaws). I'll keep this idea in the back of the mind in future and mull it over some.

    (I really don't get out much).

    Cheers,
    Paul
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  6. 25th January 2014, 07:20 PM #5
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    Thanks for the link

    Love reading old books
    regards
    Nick
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