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I"ve been asking around various lists in prep for starting O/A
welding. Would like to hear your comments on one person's input.
I had just explained that I had found a dumpster with lots of 1/8"
scrap, just right for learning the basics:
"1/8th inch is fine for farmers but you'll be farther ahead if you go
down to Home Depot and buy a couple of 10' lengths of electrical
conduit. The thin stuff (I think that's all Home Depot sells) has a
wall-thickness of about .047" -- close enough to the most common sizes
of tubing used in aircraft (ie, .035 & .049). Once you get the hang
of it, pick up some scraps of exhaust pipe tubing, which is usually
.063. What you need to learn how to do is to control the heat of the
weld well enough so that you can do a basic cluster.
EMT (ie, 'Electrical Metallic Tubing') is coated with zinc
(galvanising), epoxy and all manner of other junk. Cut the 10' pieces
into 1' coupons (ie, a 'coupon' is piece of metal used in a training
environment). If they're coated with clear epoxy, fire up your
barbeque, get a good bed of coals, and throw the coupons on the grill.
Close the thing up (aluminum foil will work) and forget about it. But
don't breath the fumes.
While you're at Home Depot, go over to the paint department and pick
up a couple of quarts of Jasco 'Prep & Prime,' which is a phosphoric
acid solution. Get a PLASTIC pail, dump in the acid and stand your
coupons in the acid. If the metal is not sealed with epoxy you'll end
up with a flat gray, zinc-free surface. Water above 200 degrees F.
will neutralize the phosphoric acid (ie, bring a bucket of water to a
boil, drop in your coupons). "1/2 inch" EMT is a nomenclature, NOT a
dimension. OD is something like .772 (but measure it; the spec isn't
very tight).
Since 1 Jan 2000 EMT is no longer marked as such and is in fact basic
welded structural tubing. (Before, the alloy used in EMT had a fairly
high lead content to facilitate bending, but the lead not only
weakened the tubing, it was an environmental hazard. Modern-day EMT
uses a new ASTME alloy, slightly superior to SAE 1025 in both strength
and formability. Although the Big Foots still frown on making
airframes from the stuff, since the spec changed in 2000 there's no
engineering basis not to use it; it's just plain old fashioned mild
steel tubing.
For practice welding rod, try bailing wire (!), also available at Home
Depot. Go back to where they have the concrete, ask for a roll of
'tie wire.' Five pound roll is about a buck. (If you ask for bailing
wire they'll direct you to the Yuppie Tool Department where they'll
expect you to pay $5 for one pound of 'Utility Wire.' Your mileage --
and prices -- may vary.)
Bailing wire is coated with graphite and oil. So wipe it off. Then
clean up the piece you're using with some CLEAN steel wool."
Comments appreciated - Mike
welding. Would like to hear your comments on one person's input.
I had just explained that I had found a dumpster with lots of 1/8"
scrap, just right for learning the basics:
"1/8th inch is fine for farmers but you'll be farther ahead if you go
down to Home Depot and buy a couple of 10' lengths of electrical
conduit. The thin stuff (I think that's all Home Depot sells) has a
wall-thickness of about .047" -- close enough to the most common sizes
of tubing used in aircraft (ie, .035 & .049). Once you get the hang
of it, pick up some scraps of exhaust pipe tubing, which is usually
.063. What you need to learn how to do is to control the heat of the
weld well enough so that you can do a basic cluster.
EMT (ie, 'Electrical Metallic Tubing') is coated with zinc
(galvanising), epoxy and all manner of other junk. Cut the 10' pieces
into 1' coupons (ie, a 'coupon' is piece of metal used in a training
environment). If they're coated with clear epoxy, fire up your
barbeque, get a good bed of coals, and throw the coupons on the grill.
Close the thing up (aluminum foil will work) and forget about it. But
don't breath the fumes.
While you're at Home Depot, go over to the paint department and pick
up a couple of quarts of Jasco 'Prep & Prime,' which is a phosphoric
acid solution. Get a PLASTIC pail, dump in the acid and stand your
coupons in the acid. If the metal is not sealed with epoxy you'll end
up with a flat gray, zinc-free surface. Water above 200 degrees F.
will neutralize the phosphoric acid (ie, bring a bucket of water to a
boil, drop in your coupons). "1/2 inch" EMT is a nomenclature, NOT a
dimension. OD is something like .772 (but measure it; the spec isn't
very tight).
Since 1 Jan 2000 EMT is no longer marked as such and is in fact basic
welded structural tubing. (Before, the alloy used in EMT had a fairly
high lead content to facilitate bending, but the lead not only
weakened the tubing, it was an environmental hazard. Modern-day EMT
uses a new ASTME alloy, slightly superior to SAE 1025 in both strength
and formability. Although the Big Foots still frown on making
airframes from the stuff, since the spec changed in 2000 there's no
engineering basis not to use it; it's just plain old fashioned mild
steel tubing.
For practice welding rod, try bailing wire (!), also available at Home
Depot. Go back to where they have the concrete, ask for a roll of
'tie wire.' Five pound roll is about a buck. (If you ask for bailing
wire they'll direct you to the Yuppie Tool Department where they'll
expect you to pay $5 for one pound of 'Utility Wire.' Your mileage --
and prices -- may vary.)
Bailing wire is coated with graphite and oil. So wipe it off. Then
clean up the piece you're using with some CLEAN steel wool."
Comments appreciated - Mike
- Mike
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