I saw a guy going over some hot-rolled steel bar with a blow torch
recently. When I asked what he was doing he said he was evaporating
the moisture from it. Sure enough - I watched it myself. The process
is that he'll fabricate the chair, blow torch the whole thing, then
rub beeswax all over it. Seems pretty labor intensive. I'm wondering
if we couldn't just put the whole dozen chairs in our wood kiln for a
few days and achieve the same effect. Any thoughts.
Also posted to rec.crafts.metalworking
Could he be burning the milling oil from the steel before he paints it?
That would be the quickest way I could think of to get rid of it
I don't think the blow torch would be hot enough to remove the stress
from the metal in the recent fabricated piece.
On Fri, 19 Sep 2008 14:52:48 -0700 (PDT), Jay Pique
My thoughts are that if it's moisture you're trying to get rid of,
just set 'em out in the open sun for a couple of hours. Refinished
some lawn furniture recently. Used a pressure washer to knock off
loose paint. Left them out in the sun for a couple of hours to dry,
set them in the shade for a couple of hours to cool off, sprayed them.
But, I don't think it was moisture the guy with the blowtorch was
after. Like another poster surmised, it was probably mill oil he was
Now that's interesting. The whole story is this. One of our guys and
a metalworker built a table for a client. It's made from pieces of
hot-rolled steel that had further been cold bent into curves. They
welded together the parts, sanded it and then applied a coat of
beeswax. And it rusted. So now the metalworker thinks that if he
heats the steel really well it will evaporate trapped moisture and
then they'll seal it out with beeswax. (I know, I know....) In any
event, since it sounds like it's not moisture they're burning off
anyhow, the whole question of whether a kiln would work is pretty much
moot. (Obviously wouldn't be hot enough to burn off oil, either.)
Now for the real question - how do we prevent this table and chairs
from rusting? Not much response from the metalworkers <grumble>.
Could we fabricate the whole chair or table, then take it someplace to
be dipped? Or do we have to assemble it from pre-dipped steel - in
which case I gather we'd have rusting issues at the welded joints,
I can't wait to unload a ration of crap....errr...."inform the
metalworkers" on Monday!
Just scorping the seats.
You need to call around to your local plating companies and find out
what size tanks they normally have set up. I'd go with chrome over
galvanized--hot dip galvanize isn't all that pretty a finish and
plated zinc isn't very hard. Nickel is _very_ tough (it's used as
protection on aircraft propellers) but doesn't stay shiny without
regular polishing. How large a piece can be handled depends on how
big a tank is available.
If the tanks are large enough they should be able to do the whole
table, although they may need to do some fiddling to get the
electrodes placed for even coverage. Welding up from precoated steel
means that you've lost the protection at the welds. A better option
might be to make it in several subassemblies that can be bolted
together--note--if you're using tapped holes, either tap them _after_
plating or plug them for plating.
This really sounds like you might be ahead of the game to use
Hamilton-Standard 54460 and 24PF are two examples that use a bonded-on
sheath over the outer portion of the blade leading edge. You can see
them on a 54460 at http://www.flickr.com/photos/goldorak/417313975 /.
The new 8-way that replaced the 54460 on the E2 is another--you can
see the sheath clearly at
http://www.flickr.com/photos/kensaviation/1896504667 /. Those sheathes
are plated on a mandrel then removed from the mandrel, trimmed, and
bonded to the blade. There is also a process involving plating nickel
over conductive rubber--the rubber prevents cracks in the nickel from
propagating into the blade. Don't recall where all that was
used--some 54H60 variants for hovercraft use had it and I recall
vaguely that it was used on the 63E60 in a similar application--it's
been a long time and the 63E60 was past its prime when I was working
If you ever fly on a propeller-driven commuter airliner, look closely
at the blades and you'll see the sheath unless it's been painted over,
which it's not supposed to be except along the edges. Carbon black in
the paint, which is electrically conductive to bleed static off the
blade, tends to corrode the nickel.
As to how I happen to know this, my first job out of college was as a
project engineer in the Blade Group at United Technologies Hamilton
Standard and my area of specialization was erosion protection.
Centrifugal force takes the ice right off outboard, the prop deicers
are on the inboard end and the spinner On an older commuter airliner
like the DHC-7 you can see the heater as a rubber piece bonded onto
In http://www.flickr.com/photos/clearskyphotography/1218007750/ you
can see the heaters on a solid aluminum blade if you look
carefully--there's a foam cuff inboard with a rubber covering, but on
top of that there's a deicer attached--you can see the edge of it
about 1/3 of the way back on the top left blade. The little tab that
sticks up is part of the heater but isn't itself heated. The shiny
strip along the leading edge is likely where dust and rain and whatnot
have eroded the anodize off the blade, although the Dutch may have
painted it for some reason. The tips would have been repainted
recently. http://www.flickr.com/photos/cmphoto/2505031128/ shows a
different model of that prop (both the P-3 and the C-130 use the 54H60
but with different blade tips--nobody ever told me why the
difference). http://www.flickr.com/photos/cmphoto/2530724870/ shows
the heater very clearly. Note the clear tape at the ends of the
heater--that's one that I haven't seen before on that prop but would
bet that it's polyurethane tape that's there to protect the outer edge
of the heater--the outer few inches of those heaters would wear
through long before the rest and the polyurethane tape was an approved
modification on the commuter airliners when I left the company--it's
very likely that someone after me got it approved for that use on the
P-3. http://www.flickr.com/photos/78436618@N00/2497802331/ is another
with a clear view of the heaters--on this one they've been cut back a
little bit--not sure if it's far enough to get into the wires or
not--but that's the area that would wear through.
Most engineers don't have time to write book every time they refer to
the mechanism by which water is retained in a bucket that is swung in
vertical circles on the end of a rope. We just call it "centrifugal
force" and recognize that that's shorthand for a long-winded
explanation and get on with life.
alright you got me there :-)
I dont recall seeing the leading edges you mention on commuter turbo
props but I'll believe you.
most props are forged 2025 aloominum with an anodised surface
hardening. the polished prop effect is achieved by wearing off all the
anodising and polishing the remaining aloominum.
the leading edge treatments I can recall are more like icing cuffs or
seriously though I do believe you on the hovercraft props.
Stealth ( Hovercraft props!?!?) Pilot
I think that the term for the sort of commercial aircraft that would
have Hamilton props is "regional" airliners these days.
The C-130 and P-3 have 7075 blades (note, not 707_6_--Hamilton props
are about the only place that 7075 is used and Alcoa used to have to
run special lots for Hamilton). The Hamilton commuter props have a
fiberglass or Kevlar shell over an aluminum spar, which may be 2024--I
honestly don't recall what they were using on those spars. The 54460
on the E-2 had a fiberglass shell over a steel spar--don't know what
they're doing on the new 8-way. If you look at the photos of that
prop on flickr you'll see that inboard of the nickel sheath the
leading edge is smooth--the deicer is molded into the fiberglass--the
wires are stitched into place during layup. The 24PF had a glue-on
rubber heater, but the newer ones have gone to the integral heater.
Here are a few that show the sheathes more or less well:
Good clear prop close-ups are rare.
By the way, those polyurethane strips--I'm the guy who got the first
one certificated, for the 24PF on the DHC-7.
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