Thursday, January 8, 2015

Gateway (28)

Post 28 in an ongoing series describing the design and construction of a kabukimon, a type of Japanese gate. Post 1 in this series can be found here if you'd like to start at the beginning. Each post links to the next at the bottom of the page. Recent installments also located in the 'Blog archive' index to the right of the page.

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After several hours of sharpening this morning, I ventured over to the shop. For some reason the electric blanket was no longer on - not sure why it had turned off as it had power. Anyway, the small umeki strip I fitted in between the mortises for the main crossbeam, kabuki, and the decorative flanking beams, kasagi, came out acceptably:


A closer look:


The other bit of patching I did yesterday, to the other nose piece's side face, came out well I thought:


Another view:


Back to the posts. With the patching work for the area out of the way, I could lay out and mortise for the kasagi:


In case you are wondering what the heck the kasagi are, here are the parts (in red) to which I am referring):


A closer look at that mortise:


There are two stub tenon mortises, and in the middle is the start of a mortise for a sliding hammerhead key. That mortise will be elongated later on. I'm waiting on the tooling.

The other post mortise for the kasagi came out similarly:


Then there was the other nose piece with the bowed kerf which I repaired yesterday:


It didn't come out as I would have liked. The kerf sidewalls were simply not even enough, even with a wedge-shaped insert strip driven in, to obtain clean join lines:


Another area with the same issue -excuse the blurry close-up attempt:


One step forward, two back. The good news is that it is relatively easy to correct such issues in patching the sewari. I milled the grooves this time, using two settings of a straight guide edge to guide the router, so the kerf has gone from bowed to being two straight runs with a slight kink:


I put that puppy in the oven (the shop washroom with the little heater, I mean) and am expecting a better result tomorrow.

All for now - thanks for dropping by and visiting. Now for post 29

8 comments:

  1. Hi Chris, didn't this gate include a roof at one point? I seem to recall a gable which was centered over the entire structure, (in side section) rather than centered over the main gate.

    Peace,
    Harlan Barnhart

    ReplyDelete
    Replies
    1. Harlan,

      did you have to remind me about that?

      Yeah, originally I pushed hard to make this project a roofed gate and the MFA was going that direction until, uh, other issues intruded. I will refer you back to post 3 in this series:

      http://thecarpentryway.blogspot.com/2013/11/gateway-iii.html

      That's what might have been. A roofed gate was but a wisp of a dream...

      ~C

      Delete
  2. Some electric blankets have a built in timer that shuts them off after so many hours.
    I am one of the blank starers on the kerf. I can see your reasoning for making it but not putting the spline in it. Wouldn't this just make it crack/split again? Or has the kerf allowed the wood to shrink/move away from so that gluing in a spline won't be a problem.

    ReplyDelete
    Replies
    1. Ralph,

      yes, my wife mentioned that some electric blankets shut off automatically when I read here the post last night. Things I didn't know.

      The insertion of a 1/4" spline into a machined 1/4" groove does not induce splitting issues, especially given that the stock with the groove in it is 7"~11" thick in most cases. The kerfs both allow the core of the material to dry evenly and provide a place for surface stresses to resolve during drying. Without the kerf, the surface would check and crack. Thus, the initial saw kerf becomes a wedge shape over time as the material dries - it allowed the wood to shrink without causing cracks and checks, just an opened-up kerf.

      The reason to put the umeki in the opened kerf is two-fold: for aesthetic purposes, and to keep the weather out. In a Japanese building, I might add, only the timbers which have all faces visible would have the kerfs patched. In most instances one or more faces of a timber are no exposed to view (buried in a wall,etc.), and thus the timber can be rotated so the kerfed face is hidden.

      I hope that all makes good sense.

      ~C

      Delete
  3. after modest mulling I concede. I must know why the nose piece tenon were roughed out leaving the bits in between cuts that made it resemble silicone earplugs or as I first thought the plastic spacer clip for a install of a new screen door. seems like quite a bit more work especially considering the Hitachi poised nearby. the work piece too tall to clear its guides perhaps.
    Rob in Erie pa
    (RLSIII)

    ReplyDelete
    Replies
    1. Rob,

      I was wondering if that cut out process would be noticed by anyone, or lead to any pondering. Of course it would seem to be so much quicker to rip the tenon waste off on the bandsaw- even with a max height of 16", I could have cut 90% of the tenon that way.

      While I considered that course of action initially. I didn't choose to do it that way however. A portion of the tenon and slot mortise are exposed to view, and I want to achieve a very good fit in that area with crisp arrises on the parts. The tenon also needs to be accurately centered on the part. The tenons are long, so to have an overly tight fit would make assembly of the pieces a hassle. The plus/minus tolerance of the fit was of concern, as was achieving clean cut out.

      A good fit, to my way of thinking, in this material over that length, would be to make the tenon thickness about 0.005" over the width dimension of the mortise. I can pre-compress the wood on the tenon easily enough to accomplish a good sliding fit. And bandsawing or other means of ripping the tenon cheeks, would not tend to achieve the desired accuracy and clean cut arrises. I could of course saw slightly wide of the line and clean up, but it seem to me to be a bit more of a hassle to plane a stopped surface evenly and flatly.

      I chose instead a method where I use a router and deck the surface of the tenon an equal amount from both faces of the stick, ending up with a very precisely dimensioned tenon thickness. Those "bits in the in between" areas serve to support the router base.

      After the router work, I trim off the portions which supported the router and then clean those areas flush to the surface with a chisel. It was obviously a bit more trouble to follow that course of action, but I knew it would give me the most accurate results, and I met my goal in that regard.

      I'll be following a slightly different process on the kabuki for its long tenons, as the amount of cut depth required from one face of the stick is too great for my router to manage, and the stick is too heavy and awkward to stuff into the bandsaw. I've got a solution though.

      Keep in mind that the wood is dry and will not be shrinking appreciably and for the most part has been stable after cutting away the tenon waste. Were the material otherwise, I would likely have rough cut the tenon waste with the bandsaw and let the part do it's moving, then set up some means of machining the tenon straight and to dimension, which would involve some sort of jig I imagine.

      Appreciate your question Rob.

      ~C

      Delete
  4. clear as day now I pondered the bits for support of the router but couldn't see the advantage until you mentioned the centered tenon. following the previous posts its obvious the tenon was meant to be centered but it didn't click. cant think of a better way to accurately center a tenon given s4s material. keep forgetting its been through the beam planer. the beams of cedar ive used to frame with in the pastwere never quite square. ah stock prep. If only I knew then what I know now
    my thanks for the detail
    Rob in Erie pa

    ReplyDelete
    Replies
    1. Rob,

      I'm glad that made sense. Yes, accurate stock prep is the key to a lot of joinery work.

      ~C

      Delete

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