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Thread: Part Deux - The Gennou BTS

  1. #16
    Interesting stuff. All the Japanes tools are pretty remote for me, but it is fun to read about.

    One think I don't understand is the aversion against wedges. Billions of hammers, axes and whatnot have a wedge to hold the handle to the head. They don't seem to cause a lot of problems overall. Why making a problem of it?

  2. #17
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    Quote Originally Posted by Kees Heiden View Post
    Interesting stuff. All the Japanes tools are pretty remote for me, but it is fun to read about.

    One think I don't understand is the aversion against wedges. Billions of hammers, axes and whatnot have a wedge to hold the handle to the head. They don't seem to cause a lot of problems overall. Why making a problem of it?
    Kees,

    Notice how small the eye is. A wedge through that will weaken it unless the handle is really fat below the tenon. All a wedge does is either splay the tenon in a tapered eye, or compensate for poor tolerances in either the eye or the tenon.

    This is a Formula 1 race car type handle, so it does not handle a trailer hitch well.

    Stan

  3. #18
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    Quote Originally Posted by Derek Cohen View Post
    Stan, a question for you that I do not recall being asked (or answered) ..

    Why is the handle bent? How does this differ from a straight handle? (OK, two questions ).

    Regards from Perth

    Derek
    Derek,

    I thought both points were covered in my original post, but I will try to clarify. Sorry for the confusion.

    The handle is bent, and differs from a straight handle, for two reasons.

    First, the wrist tends to naturally lead the head when swinging a hammer, causing the axis of the head to be rotated out of alignment with the axis of nail or chisel being struck. This is not efficient. Angling the head away from perpendicular to the handle helps bring the head back into proper alignment at Impact improving energy efficiency, increasing cutting or nailing precision, and with straighter rebound, rhythm and speed as well. Please try the inkpad test in my first post.

    Second, and intimately related to the first reason, this handle locates the wrist and hand where they are most efficient in relation to the point of impact.

    Give it a try.

    Stan
    Last edited by Stanley Covington; 05-20-2016 at 4:01 AM.

  4. #19
    Quote Originally Posted by Stanley Covington View Post
    Kees,

    Notice how small the eye is. A wedge through that will weaken it unless the handle is really fat below the tenon. All a wedge does is either splay the tenon in a tapered eye, or compensate for poor tolerances in either the eye or the tenon.

    This is a Formula 1 race car type handle, so it does not handle a trailer hitch well.

    Stan
    Well, make the hole larger, problem solved!

    Probably some eastern-western philosophy thing, which might be one of the reasons that it all remains fairly remote to me.

  5. #20
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    Quote Originally Posted by Kees Heiden View Post
    Well, make the hole larger, problem solved!

    Probably some eastern-western philosophy thing, which might be one of the reasons that it all remains fairly remote to me.
    Make your handle like a guy that knows how to work wood....Problem solved!

  6. #21
    And take a blacksmith that makes the hole exactly right.

  7. #22
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    Quote Originally Posted by Stanley Covington View Post
    Derek,

    I thought both points were covered in my original post, but I will try to clarify. Sorry for the confusion.

    The handle is bent, and differs from a straight handle, for two reasons.

    First, the wrist tends to naturally lead the head when swinging a hammer, causing the axis of the head to be rotated out of alignment with the axis of nail or chisel being struck. This is not efficient. Angling the head away from perpendicular to the handle helps bring the head back into proper alignment at Impact improving energy efficiency, increasing cutting or nailing precision, and with straighter rebound, rhythm and speed as well. Please try the inkpad test in my first post.

    Second, and intimately related to the first reason, this handle locates the wrist and hand where they are most efficient in relation to the point of impact.

    Give it a try.

    Stan
    Easy enough Stan - I'll simply turn the gennou around and use the other side

    Regards from Perth

    Derek

  8. #23
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    Quote Originally Posted by Derek Cohen View Post
    Easy enough Stan - I'll simply turn the gennou around and use the other side

    Regards from Perth

    Derek
    Derek:

    Sounds like an excellent idea. Its a beautiful handle.

    Please let us know if it makes a difference. In the case of your squat daruma, it may not be obvious.

    Stan
    Last edited by Stanley Covington; 05-20-2016 at 8:23 AM.

  9. #24
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    Stan (and others), many thanks for taking the time to document your thoughts and experience. However, you're killing me. I've been smitten with the Tenryu tsuchime gennou since Derek posted photos of his. I may have to pull the trigger even though it would be the cart before the horse as I've also been resisting buying a set of japanese chisels...

    I've gathered that a ~225 g head is favored by most for general light bench work and heavier (e.g. 375 g+) are best for mortising and chopping? It is tempting to order a 225 g shikaku and a 375 g daruma and try both, but that's not a luxury I can afford right now.. FWIW, I currently use a 18 oz Wood is Good mallet for most everything. Any suggestions?

    Thanks!
    C
    "You can observe a lot just by watching."
    --Yogi Berra

  10. #25
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    Quote Originally Posted by Christopher Charles View Post
    I've gathered that a ~225 g head is favored by most for general light bench work and heavier (e.g. 375 g+) are best for mortising and chopping? It is tempting to order a 225 g shikaku and a 375 g daruma and try both, but that's not a luxury I can afford right now.. FWIW, I currently use a 18 oz Wood is Good mallet for most everything. Any suggestions?

    Thanks!
    C
    Christopher:

    Not sure what the question is, but I will throw some suggestions out.

    As you mentioned, the style and weight of hammer you order should depend on what kind of work you are going to do.

    Non-Japanese seem to like the daruma style, and although I own and use them myself, they are a specialist style not intended for general use. In fact, they are thought by many here in Japan to be ugly little fellas used by guys who can't find the end of their chisel or the head of the nail. I have seen carpenters ridicule other carpenters who bring a daruma to the jobsite. They are used a lot by carvers and tategushi (joiners) but for different reasons.

    For most applications, a standard ryoguchi head, which is longer and thinner than the daruma, is preferred because it is stabler (larger moment of intertia) and therefore resists twisting out of alignment during the swing better. This makes it easier to use from different heights and different angles. It also has less air resistance. But, if like a joiner, you need to sit down to cut 300 identical small joints from a fixed position and height and angle in a couple of hours, then the daruma is the way to go

    Of course, I am just talking about physics. One can do very good work with a daruma in all situations. The prejudice against the ungraceful appearance of the daruma is a matter of fashion I suppose.

    If you are a carpenter, then the 375 (100匁) gennou is the standard general purpose weight gennou head. When using tataki nomi for cutting deep and wide mortises in timbers, or 16d or large nails, heavier gennou are necessary.

    For most of the small joints guys make for furniture or cabinetwork as a hobby, the 60匁 (224gram) is very good, especially for very precise work. 80匁 (300gm) is a good choice too with more chopping power. Really, you need a several. 375 would not be my first choice for furniture or cabinet work.

    I hope this rambling answered your questions.

    Stan
    Last edited by Stanley Covington; 05-20-2016 at 7:38 PM.

  11. #26
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    Thanks Stan.

    You are correct--I did not ask a clear question. I do indeed do primarily small scale work/furniture rather than larger scale work such as carpentry or cut large mortises.

    I'll likely end up with several in the end, but the question I was trying to ask was, if just one for now, which weight? And which style? My thanks for your providing some good info on both questions and based on my reading, you'd suggest a ~225 g daruma as a good staring spot.

    I'll be interested to hear what other say about which weights and styles they use most often.

    Best,
    C
    "You can observe a lot just by watching."
    --Yogi Berra

  12. #27
    Chris,

    I had the same questions as you, and got them very well answered by Stan via email/chat etc.


    What's your price range?

    You could always start with a simple "user grade" dogyu hammer from Stu (tools from Japan) http://www.toolsfromjapan.com/store/...44_369_470_471 or Hida Tool http://www.hidatool.com/woodworking/hammers and move to the "connoisseur grade" stuff after you've used your hammer for a few months/years. It'll be under $40 a hammer. Get both a 225 and 300 g hammer from Stu for under $40!
    Personally, I'd avoid fancy finishes, gold plating, etc.
    I'd avoid a daruma for your first one (it's actually sorta cumbersome in the hand--much less precise feeling, especially for small joints like in chairs, small furniture).
    If you don't hit the thing dead center, it sort of twists a little (although people like Derek Cohen seem to make a great job with it).

    Definitely go and make your own handle--it just costs a trip to the firewood pit (unless you're a nut like me, where I got hand split billets of osage orange billets off ebay).
    A bent handle feels much more natural in swing...and it's much more satisfying.

    After using both for a few months, splurge.


    I'd recommend a Hiroki or Kosaburo (major brag, thanks Stan!) if you can afford it, as they are both incredibly well made.
    I have a Hiroki 180 g from Deiter Schmidt (used mainly for chopping very precise notches in spruce guitar bracing) and a 375 Kosaburo from Stan.
    If Stan didn't tell me it's from Kosaburo, I would not know the difference as fit, finish, balance, workmanship are both at a sublime level.

    Before getting the Hiroki, I never understood the fascination/obsession with gennou that the Japanese have.
    After ( with the right handle (self-made of course)), I can COMPLETELY understand what it's about--the feeling of the head sucking down on a well honed chisel is a feeling that is so "right" that I feel like crying manly tears of gratitude.

    -Matt

    ps. You may want to PM/email Stan regarding chisels/gennou. I was really impressed with his "user grade chisels" that cut at least as nice as my Masashige.
    I think that he's also got some new guy making inexpensive, high quality HSS chisels (not bad if you're abusive on your tools, and don't want to baby them.
    He is a wealth of knowledge and loves Japanese tools.

  13. #28
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    Stan's 'user grade' chisels are superb. They outperform the Yamahiro mortise chisels that I have, holding an edge at a shallower angle.

    The Tenryuu is nice, but there is something just incredible about Kosaburo and Hiroki gennou.
    Last edited by Brian Holcombe; 05-21-2016 at 7:08 AM.
    Bumbling forward into the unknown.

  14. #29
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    Quote Originally Posted by Stanley Covington View Post
    Derek:

    Sounds like an excellent idea. Its a beautiful handle.

    Please let us know if it makes a difference. In the case of your squat daruma, it may not be obvious.

    Stan
    Well Stan, I had a chance to install butt hinges today and used the gennou.

    I do agree with you - I now much prefer the curve away from me. The gennou felt more controlled.

    Regards from Perth

    Derek

  15. #30
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    Quote Originally Posted by Derek Cohen View Post
    Well Stan, I had a chance to install butt hinges today and used the gennou.

    I do agree with you - I now much prefer the curve away from me. The gennou felt more controlled.

    Regards from Perth

    Derek
    Derek:

    Thanks for the update.

    You make beautiful things from beautiful wood, Derek, that gennou included. May it serve you well and long.

    Stan

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