> SAFETY ITEM
>Most engineers are aware of the danger of grinding
>aluminium and steel or cast iron with the same
>appliance. I'm sending the following details of an
>incident that has happened to me while using a 1"
belt >grinder. In January I was using the grinder to
smooth >the edge of a hacksaw cut on a 2" length of
1.1/2" >angle iron. I had been grinding for about
1.1/2 to 2
>minutes when there was a loud 'thump' accompanied by
>an approximately 2ft diameter brilliant yellow-orange
>fireball. The fireball lasted not more than half a
>second and then completely extinguished itself. It
>completely enveloped the machine and my hands to
>halfway up my forearms and to the top of my stomach.
>As soon as it went out it was obvious that I had
>suffered some serious burns to my hands, as besides
>large white areas on the heel of each thumb and the
>palm of my left hand, the skin was hanging from the
>heel of both hands from my little finger to my wrist
>and from the finger joint of my left hand. Also the
>right cuff of my shirt was smouldering, my face felt
>burning, and I could hear the front of my hair
>sizzling. Nothing on the bench was burning. The
only >evidence was a few streaks of white powder on
the >bench top and on a few items lying on the bench.
The >workshop was filled with dense white smoke with
very >little odour. Initially I could not understand
how I >could have suffered such severe burns from such
a >brief exposure to the heat. Later that evening
after >some thinking and questioning of my son (who
also uses >my workshop) it became clear what had
happened.
> A few days earlier he had ground the heads of
about >12 aluminium pop rivets. Finely divided
aluminium >mixed with finely divided ferrous oxide
produces a >compound called thermite. Thermite is used
to fill >incendiary bombs and commercially to weld
large steel >items, i.e. railway rails into continuous
lengths. >It burns at approximately 35000C (63000F)
hence the >extensive burns from such a short exposure
time. The >end result was, excluding my fingers; I
suffered deep >second-degree burns to about 60% of my
left hand and >50% of my right hand.
>
> In light of my experience, I feel there should be a
>very strong warning passed on to the readership as to
>the dangers posed by grinding steel after having
>ground aluminium, unless the machine is thoroughly
>cleaned of all aluminium dust. The potential is
>certainly there for even more serious injury.
=====
Bruce Robertson "MrMomo"
1990 Rio Red Honda CRX DX
1966 B.R.Green Triumph TR4A
1991 Custom F350 Dually flatbed
Age unknown: Highly modified John Deere tractor.
"If more is better, too much is never enough"-ec
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