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Re: :: Re: [medievalsawdust] Another basic question

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  • rmhowe
    ... You know I hadn t either. That s a good point. Most wood (and plywood) expands/contracts about 1 1/2% along the grain but as much as 6-8% across the grain
    Message 1 of 9 , Jul 6, 2003
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      Schuster, Robert L. wrote:
      > And make the holes for the rivets oversized, so there
      > is room for movement. Otherwise it's likely to warp when the humidity
      > changes.

      > --nice piece of advise there Colin
      > i hadn't considered this.
      >
      > Halvgrimr

      You know I hadn't either. That's a good point.

      Most wood (and plywood) expands/contracts about 1 1/2% along
      the grain but as much as 6-8% across the grain depending
      on species and humidity.

      When I look at rivets for bosses or ship's roves (rivets) I am
      frequently amazed by the huge heads on these things - meaning
      how flat and wide they are. It seems to be (by some experience)
      that normal mild steel won't spread that far - I'm fairly sure
      it won't without splitting or by heating and hammering a lot.

      In normal riveting which we do in armor making the mild steel
      rivets we normally use should be clipped off at 1 1/2 times
      the shank diameter of the rivet past the point where it emerges
      through the materials. This wouldn't make the large, flat, wide
      heads I normally associate with the shield rivets I've seen in
      most archaeological depictions, and I don't see regular rust
      spreading out that far beyond the edges. The size of their
      rivet shanks was probably much larger than ours.

      What they had was wrought iron, or iron that has had about 7
      percent silaceous slag hammered back into it to make it workable
      after smelting. I've never tried to rivet with this stuff with
      a narrow crosspeen hammer but it must work much differently
      before work hardening.

      Maybe an air hammer might produce fast enough blows to cause
      enough friction from metal movement producing heat and
      preventing work hardening enough to spread the rivet head out
      to look like the real stuff, but somehow I doubt it. I'm
      certain that hand hammering won't. Or did they put it in
      red hot?

      Magnus
    • rmhowe
      ... Yeah but we re all been eating out of aluminum pots and pans all our lives, and consuming candy wrapped in aluminum foil as well. I don t think you can
      Message 2 of 9 , Sep 1, 2003
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        Bruce S. R. Lee wrote:
        > Be very careful with 'burning' any coating off metal parts - be they bolts,
        > nuts or pipe. These days you have to be a metallurgist to tell exactly
        > what's in the metal coating - some hardware has cadmium plating, and even
        > zinc (real gal) is not too good for you in the long run, and for
        > 'zincalume' plating there is the theory about aluminum & Alzheimers....;-(

        Yeah but we're all been eating out of aluminum pots and pans
        all our lives, and consuming candy wrapped in aluminum foil
        as well. I don't think you can avoid aluminum much in the
        modern world. There are lots of soft drinks with citric
        acid in them in aluminum cans, and for many there is BEER...

        MajicBadger used to smelt brass in his open forge to cast it.
        What happened to him was BrassFounders Ague. Massive headaches,
        various other bodily syptoms for quite a while. I am told it
        is rather like malaria at times. Eventually goes away.

        I've seen Master Eldred cast with a cutting torch as a heater
        and trying to stand out of the huge amounts of fumes as the
        zinc gradually burned out of the brass. Tin/copper makes Bronze.
        I think he may have had milder symptoms. He melted in
        an open crucible and poured it into wooden or metal
        sand casting flasks right on top of a block wall.
        Still in one piece. Some folks are just lucky.

        I recommend casting over a sand table with a splashguard
        on your side of it. In industrial arts our casting sand
        table was low but it was on rollers. Melted metals which
        are hot enough can hit concrete, and spall themselves
        and bits of the concrete off by a steam reaction from
        liberating the water in the concrete. Happens very fast
        I am told.

        Cadmium is considered quite hazardous, particularly in the
        jewelery field where it was in so many solders. I once read
        that jewelers (and welders) have about ten years less life-
        span. Many plating solutions were cyanide based - most
        of the briter ones. I'm not sure if someone has licked
        the silver plating without cyanide successfully yet.
        This is why I have three fume hoods to install in
        my shop as well as a localized movable dust extraction
        system with a much smaller micron bag to add to it.

        I had tried doing bone carving, which I love, and I was
        producing a few really good pieces. Unfortunately the
        muscles in my arms and back won't handle it now and
        I am going to have to switch over to electrical rotary
        tools and pneumatic engravers. The high rpm ruby burrs
        scare the mess out of me making dust that tiny. After
        a particle size gets too small your cilia in the lungs
        can't expel it as it gets below the cilia heads.

        Two years ago I damned near died of something causing
        pneumonia (that was not showing the symptoms I am familiar
        with from two previous bouts of pneumonia, and two of
        pleurisy. So I rather suspect the bone dust. Fever of 105
        when they started treating me. Two days on anti-biotic
        IVs in the emergency room and intensive care. Amazing
        how quick they can cure you these days. I think the
        bill was in the $5200 range for two days.

        > Better to give it a good grinding first to get the
        > plating off the exposed
        > bits before heating to give it a 'patina'.

        Sounds like good advice.
        I once got chromic acid poisoning from rewelding
        plastic bottoms on some tanks used for cleaning
        glass for the electronics firms. I used to make
        a good portion of the plastic equipment (up to
        huge size) for the industries here in NC/SC/VA.

        Even made a gold plating table once with four
        drop in tanks that over flowed into each other.
        No drain, raised flanges had to fit under the
        U shaped edges of the tanks which fit into a
        depressed center table which I had to make a
        lapped frame cut hollow underneath.
        Rarely got the easy work. Wish I had more
        pictures of things I've built like that one.

        I should like to add never to grind aluminum and steel or
        iron and have it fall into the same pile. If it ignites
        it causes a very high heat thermite reaction. One man
        wrote into a magazine saying he had been badly burned
        on his hands. Came to find out that his son had been
        grinding aluminum on his belt sander the day before.
        When he ground steel and it produced the usual sparks,
        the pile of dust was ignited. You can actually weld
        underwater with a thermite reaction. They use it on
        such things as welding some railroad rails and
        ship repairs. Grinding steel and aluminum on the same
        belt sander was quite common when we used my equipment
        for armoring and I never really considered it dangerous.
        I thought you had to have a magnesium strip to get enough
        heat to ignite it. Apparently not, so it's good to note
        above the sander. That particular one was a 1 x 42".

        I hope most folks know not to grind metal other than
        ferrous (steel/iron) on a grinding wheel used dry.
        It will load the wheel up and make it useless.
        Sanding belts don't load with metal like that.
        Neither do ScotchBrite wheels, but I imagine few
        peole outside the metal or jewelry industry use them.

        > If you REALLY have to burn
        > something, do it way, way outside on a day with a stiff breeze & keep an
        > eye out for the EPA.

        Why I put wheels on some items. Like the bandsaw
        and a rolling metal table suitable for putting
        smaller machines/grinders/sanders/etc. on.
        To take them outdoors.
        Some dusts are really irritating.
        Bone, Horn, Antler - all stink when you are working
        them. All go all over the house from the basement
        shop. Very fine airborne dusts.

        Saw on another list that Tandy is claiming
        their horns are only for "decorative purposes" now.
        Someone had written them wanting to know what the
        strong chemical smell in the horns was now. They
        wouldn't say. Instead they recommended another
        horn dealer.

        I've seen the OSHA folks walk right into all eight of
        my former university's physical plant shops and shut
        down half our equipment, none of which we could use
        again until we matched up to their specifications
        as regarded guards and blade covers. I had to refit
        three shops worth myself. All of a sudden we got all
        kinds of things we'd been wanting. Fortunately I knew
        what the best things on the market at that time were
        when the state coffers finally opened.

        Previously the state was somewhat immune to OSHA and didn't
        care about what happened to the employees. One turned
        them in and they got 17 citations in one day from only
        two job sites. They should have seen the ones we were
        working on. Far worse than the citations.
        Of course he got fired for "falsifying something" on his
        job application the next day or two.

        The rest of us all of a sudden got saddled with all
        kinds of safety gear from special shoes to powered
        dust hoods for the glasses wearing and fume masks
        for the rest. No more paper filters for us. Dammit.

        We never were able to finally get a suitable guard
        for the big swing-saw we used to use to cut heavy
        stuff to length. The saw blade was suspended on
        a swinging trunnion, and you pulled the saw towards
        you. Rather like a radial arm saw without all the
        fancy angles. Very powerful. Almost cut through a
        6X6. I disabled before I fixed that one, the last
        machine. Surplused after I left with a lot of machines
        from very many shops on campus. There were at least
        four machine shops and the design school shop that
        had nothing to do with us there. I don't know what
        the vocational ed folks had. Never saw their shop.
        I was in industrial arts - now technical education
        with half the machines surplused to make room for
        the computers.

        I am seeing more and more warnings in magazines now
        that wood dusts are carcinogenic (cancer causing).

        This first was looked at in Japan and later the U.S.
        and they determined that it was mostly nasal cancers
        related to sanding and finishing. That finer particulate
        matter again. Having worked many, many thousands of
        board feet myself in many species ya gotta wonder.

        I know poplar dust used to crack my nasal membranes
        after the dust dried them out.

        Now the medieval man who used axes, adzes, chisels,
        and sometimes saws and boring tools rarely made such
        a dusty mess of himself.

        Magnus

        >
        > regards
        > Brusi
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