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Re: [medievalsawdust] Plan for Cedar

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  • rmhowe
    ... You may never have encountered case hardening in unequally dried wood. This usually means the outside is drier than the inside [or vice versa] and the wood
    Message 1 of 8 , Oct 12, 2004
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      Dragano Abbruciati wrote:
      > Okay - that's why I asked.
      >
      > Bill McNutt <mcnutt@...> wrote:
      >
      > That's too thin, bwana. They'll split/warp.
      >
      > Rip them to 1 3/4" for drying, then again to 3/4 when you're ready to
      > start work.

      You may never have encountered case hardening in unequally dried wood.
      This usually means the outside is drier than the inside [or vice
      versa] and the wood can bend out from the kerf or close it entirely.

      The last is by far the most dangerous. The former is why the really
      old model tablesaws had the fence end stopping near the mid point
      of the blade. It prevented the wood between the blade and the fence
      from bellying itself back into the backside of the blade as it cut.
      Not very many mills and wood suppliers [or shops for that matter]
      had moisture meters back then. Not everyone knew how to cut wood
      accurately and weigh it for moisture content by species either
      which was the alternative. Generally it takes a year per inch
      of thickness for air-drying assuming you don't live in a high
      humidity area. Wood being hygroscopic it can gain and lose
      moisture content from the air.

      Apart from the fact that unequal drying causes board warping
      when cut it can also clamp right down on the saw blade so hard
      [even with a 7 1/2 hp saw] it will stop it and that you may find
      you can't safely let it go with a single hand to turn off the
      saw motor before it burns it out. Saw motors are seldom cheap,
      it halts production for days sometimes. Single phase capacitors
      that can burn out when the starting windings come back on at
      lower speeds (the starter winding's centrifugal cut off switch
      in the motor reengages) are much faster to replace but still a
      pain to go get from a motor repair or electrical supply shop
      {assuming you know how to use a multi-meter to diagnose whether
      you have burnt out windings or one or sometimes two burnt
      out capacitors.

      Having fixed large machinery for years in many shops I have a
      bit of experience with this. Specific training in it too.

      At one furniture shop I ran we occaisionally encountered
      this in the thicker stuff [in our case usually maple] and being as
      how I had a foot thick+ solid brick wall behind me I decided it was
      better to sidestep and simply let go. We'd already crosscut the
      pieces to appropriate lengths after we'd marked out the patterns
      on them for the larger pieces for the legs, etc. Smaller chunks
      got used for stretchers, etc. So we aren't talking whole planks
      flying through the air here. The thinner stuff usually wasn't
      that much of a problem as the thicker woods.

      Figure a 7 1/2 hp saw operating at 3450 or so rpm x 14"
      [blade size] x 3.14 [circumference] divided by 12 inches to
      obtain feet per minute or you can divide it further
      by 60 (for seconds) and you can come up with some terrific
      velocities should you NOT be able to hold the -now clamped itself
      to the blade- piece safely with only ONE hand while you try to turn
      it off. I certainly have.

      I've seen huge boards thrown 50 feet down the length of a very
      large shop horizontally right into the end doors by some morons
      who took their hands off of or backed up on a cut on them.
      You only have to back up a small amount for the saw to grab
      and throw the boards sometimes.

      I saw one moron on a -huge- saw simply stop in mid kerf and
      walk away to talk to someone when two guys were behind him
      downrange of the very same saw. As they were bent
      down working at the time it may well have proved deadly.
      Then he had the gall to get mad when I cussed him out about
      nearly killing his co-workers. I'd gotten there as fast as
      I could to grab the plank (a ten foot 2x10) and turn the
      saw off. Wish I'd had the power to fire him, but then I was
      working for the state then. If it had been one of the shops I
      had run as the foreman he would have been gone immediately.

      Having twice been hit really good and hard with a chunk of wood and
      a chunk of plastic {that one caused a foot sole sized instant purple/
      yellow bruise on my abomen} I'd rather sidestep and let go myself
      assuming no one was behind me. The wood one happened one of the
      first times I ever operated a large sized tablesaw in Industrial
      Arts woodshop class and the other happened when I was the main
      fabricator in a plastics plant and the open bottomed saw box managed
      to fill itself up with 6" shreds of the 3/4" thick plastic I couldn't
      see [or imagine] that I was cutting with a rip-saw and it grabbed
      a wad of those and brought it into the saw kerf thereby throwing
      the piece at me. IF there had been a point on it it would have
      gone through me I believe. If the blade is stopped when you let
      go you should have time to get your fingers by if you are fast.

      Although I suspect if you rip it ala Roy style with a handsaw you may
      not encounter the velocity. You might have the bottom few inches of
      the board split suddenly instead. This can happen on a tablesaw
      as well.

      There was a very interesting article in Woodwork about two/three
      years ago on how the English joiners may very well have cut their
      pieces to over-length and then split them a bit oversized with
      a froe, and then put them aside to air dry for making into joint
      stools, etc.

      >
      > Just my two drachmas. I've only worked "from the log" a couple of times
      > myself, take it for what it's worth.
      >
      > Will

      I really hope I don't ever repeat the experience I once had working as
      the head cabinetmaker at NCSU my last eight years [before I became
      disabled with a neuro/muscular disease].

      Some idiot [minor department head] had the idea of slabbing out
      a large tree that had grown on the campus for most of it's then
      hundred years and died. They cut it down and we had to slab
      large chunks of the thing on a huge 36" woodshop vertical bandsaw.
      This involved making a cradle to use in conjuction with the
      fence and screwing the ends of it to the log. One end was made
      movable in the length of the cradle, one end was simply fixed
      to the side and base of it. The whole thing was slid through
      carefully by two of us in the process.

      We had imagined that it would be put to some commemorative use.
      We used to make various plaques and awards for the university
      to give, and even the moldings for frames for paper ones, with
      custom ground shaper knives made by me, right in the shop.
      That is an interesting experience - making duplicate blades
      that have to be correct and blalanced to clamp into a corrugated
      head that revolves at high speed. So after making some really
      odd other stuff this request didn't seem that out of bounds.

      After we busted our a**es for a couple of days and finished the
      job we learned the idiot thought the wood would be useful for
      stakes for landscaping purposes.

      I wished I'd had the remainder of the tree to beat him ugly with.
      Of course he may have been operating on the rule that we'd get fired
      for doing so. For the labor it cost it would have been cheaper to
      buy the wood by far finished. When the story got back to the senior
      budget supervisors he had a bit of serious explaining to do.
      Either way he was thereafter correctly labeled an idiot in his
      branch of the department and his ability to generate work order
      requests from other branches was severely curtailed without
      higher approval.

      > -----Original Message-----
      > From: Dragano Abbruciati de Genoese
      > [mailto:dragano_abbruciati@...]
      >
      > I will then "quarter-saw" the logs and rip (with a hand saw) the
      > boards to about 3/4" thickness. I will reseal any ends that need to
      > be redone and stack the boards (1" air space all the way around) for
      > drying. I don't have an attic and I don't have room in the house for
      > this process, so my shed will have to do.

      Or a good tarp. The problem is when case hardening begins an experienced
      kiln operator will realize it and rewet the outside of the boards so the
      pressures can equalize in the wood and allow it to dry correctly slower
      again. They actually spray them with garden hoses with sprinkler heads
      sometimes. An amateur may well have no idea it is happening or what
      to do about it. Humidity is generally adjusted in kilns, as is
      ventilation and heat.

      However, I do have some shelves in my shed covered with various chunks
      of pear and fruit trees that I hope one day to turn. The wife end-
      coated those for me.

      I've worked many tens of thousands of board feet at least in thicknesses
      up to 5+ inches or so. You never want to be one of five or six men
      having to handle a huge 5 or 6" thick, 2' wide, 16' long mahogany board.
      Moving them from a shed and then cutting them for huge bedpost blanks
      was a real struggle. It was anything but fun. That will herniate you.
      I'm still dealing with the results of a smashed toe from a 2 1/2" thick
      oak plank a quarter the size that some idiot let go of his side of
      when we were pulling it out of a rack. I still think of him fondly
      when I have a large hammer in hand. The doctor did less than a
      complete job of burning out the nail producing cells and it grew
      back in badly. Ever see Mel Gibson in Payback?

      Magnus
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