Re: :: Re: [medievalsawdust] Another basic question
- Schuster, Robert L. wrote:
> And make the holes for the rivets oversized, so thereYou know I hadn't either. That's a good point.
> is room for movement. Otherwise it's likely to warp when the humidity
> --nice piece of advise there Colin
> i hadn't considered this.
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
- Bruce S. R. Lee wrote:
> Be very careful with 'burning' any coating off metal parts - be they bolts,Yeah but we're all been eating out of aluminum pots and pans
> 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....;-(
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 theSounds like good advice.
> plating off the exposed
> bits before heating to give it a 'patina'.
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 burnWhy I put wheels on some items. Like the bandsaw
> something, do it way, way outside on a day with a stiff breeze & keep an
> eye out for the EPA.
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
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
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.