A few days ago, a foot broke off of my wife's favorite colander. I was
going to replace the colander, but she has had for at least 30 years,
and likes its now uncommon wide and shallow shape. So, I must repair it.
The colander is completely made of stainless steel, the bowl being about
12" in diameter and 5" deep. Alloy unknown, but it is not magnetic.
Fabrication was a bit sloppy. Each foot is spot-welded to the bowl in
three places, at least in theory. The foot that came off instead had
one weld plus two good-intention dents, and the one weld eventually
fatigued and broke. The other two feet were each missing at least one
weld, but it was hard to tell without pulling the joint apart.
I don't have a welder, and silver brazing was going to leave a very
large and ugly heat-affected zone, which could well rust. (Not knowing
the alloy, I have to assume that it is one of those that can rust if
raised to red heat.)
So, I drilled foot and bowl to accept three stainless steel 2-56 machine
screws and nuts, with the screwheads inside the bowl. I also put one
screw apiece in the other two feet, replacing the most obvious missing
welds. The bits of screw shaft protruding from the nuts were then
peened over with a ball peen hammer to form a rough rivethead.
So far so good - it will not fail in my lifetime. But it does look a
bit crude, and the peened thread ends are a bit sharp (as I didn't form
a real rivethead), and I think real rivets would have been better.
Copper is probably too weak, ordinary steel rusts, so the rivets should
be made of stainless steel.
The question is what alloys are best for making SS rivets. This is two
questions, actually, as one may wish to cold rivet (as I did with the
2-56 screws), or hot-rivet.
Whatever alloy those SS 2-56 screws are made of certainly would work as
a rivet. These screws were intended for use on airplanes, as the
flat-head screws have 100-degree heads, so they were probably made to
some MIL-SPEC.
Googling on "stainless steel rivet" yields that lots of rivets are made
of 304 and 316 alloys, so perhaps that's the best answer, at least for
cold riveting. But then there is hot riveting, where the rivet is
heated red hot before hammering into shape.
Joe Gwinn
All stainless pop rivets. I get them from an outfit in Phoenix for marine
work. I've got several bags of them in various length 1/8 inch diameter
hanging from the pegboard in the shop. No clue what alloy they are. They
pop in easily enough. I suppose for "finish" work I could knock out the
stub of the stem, and then used a center punch and then pin punch to spread
and flatten the pull side.
Stanley does or did make stainless pop rivets. 1/8" dia X 1/2" long is
part # PTT48, bar code 45731 13090. The store where I found them sells
imports, closeouts and overstock so I don't know a good quick source
elsewhere.
jsw
I do not think that hot riveting would have any benefits. The length
of the shank is maybe 1/16th of an inch. Not a lot of shrinkage in
that short a length.
=20
Dan
I didn't consider pop rivets because they yield this big sharp thing on
the blind side, and are weak relative to bolting or solid rivets. There
is actually a lot of force on these feet, given the leverage and general
banging around any kitchen implement receives.
The drive the stem out and upset with a punch approach will improve
strength and appearance but sounds like as much work as upsetting a
solid rivet, and yields something not as neat looking.
Joe Gwinn
Thanks Tawm, but I have already drilled the welds out and bolted it, so
now I'm more or less committed to replacing the peened-over bolting with
rivets, which are also very common in cookware.
Joe Gwinn
In article
,
" snipped-for-privacy@krl.org" wrote:
I think you are right that these rivets are too small. I was asking
more for future reference than current need.
Joe Gwinn
In article
,
"Denis G." wrote:
I did think of this, but there is a twist. The bowl material is too
thin to countersink, but there is a standard dodge from the airplane
industry - one countersinks the piece to which the sheet will be riveted
(the foot in the present example), and dimples the (bowl) sheet to
match. But it's going to require some tooling to make those dimples in
stainless steel sheet.
This dimple-the-sheet method is the reason for 100 degree flathead
screw/rivet heads: In WW2, it was found that the aluminum sheet used
for airplane skins could be cold dimpled to 100 degrees included angle
without cracking, but 82 degrees was too severe. (Don't know about the
90 degree heads used in metric screws, but I bet that 90 degrees is also
too severe.)
Joe Gwinn
The color was no issue - milady would not have cared, and copper is easy
to get and to form.
My worry is that copper is too soft and weak for such rivets to work for
long. The colander foot is fairly long compared to the space between
the welds/rivets, so the leverage is large, and I figured it would shear
off the first time the colander was dropped.
Joe Gwinn
[snip]
I agree with the make-it-a-feature approach for sure.
As discussed in my answer to Gunner, I didn't think that copper was
strong enough. Nor do I have space for 1/4" rivets - the foot might be
1/2" wide. The holes I drilled are 3/32" diameter.
So, button-head or truss-head SS rivets may be the solution.
Joe Gwinn
You are making a lot out of a simple task. Countersink the foot if you
like, then pound the rivet head and the bowl into it with a flat piece
of steel drilled for the rivet shank. For neatness you could pull the
shank only enough to snug it in the hole, then remove it, Flare the
end with a center punch and knock it down with a ball pein hammer.
In my experience salvaging stuff the sheet metal will deform
considerably before a stainless steel pop rivet breaks.
jsw
The flue pipe was joined with stainless pop rivets. The circular
flange is on the end of the main section and the straight piece beyond
it, nearest the anvil, is separate. That flange took a lot of work to
make the end a light press fit into a Metalbestos chimney. I saw no
sign of cracking despite all the hammering back and forth.
As usual I found a source for commercial parts only after making my
own, so that section of flue is out in the woods under the snow with
other second-hand stainless now.
Look at the cat con heat shield photo to see how much abuse stainless
can stand. The sheet was originally the outer shell of Metalbestos
chimney and I opened up the hem and hammered it out flat without
cracking. The curved louver slots were slit with a chisel, pounded
back flat, then hammered into a groove in the edge of a disk. Crimping
pliers tapered the ends.
I've hammered other stainless steel cookware into costume armor
without breaking it. IIRC the rivets were cut from stainless steel
woodscrews.
jsw
Rivets should make a strong reliable repair, and look good, too. My concern
would be if drilling holes in the legs would make them weaker.
Another option would be to solder the legs on with lead-free silver bearing
solder (tin with 5-6% silver) such as Harris Stay-Brite #8 and a flux
suitable for stainless steel (Harris Stay-clean).
The Harris #8 solder doesn't require a torch, so it won't cause discoloring
or rusting. The working temperatures are 430-530F, so it wouldn't be
suitable for cookware or utensils subjected to cooking temps.
Well, It's too late now, but any metal fabricator that does any work
in stainless steel will have a spot welder that could have quickly
fixed your problem. The last time I had a stainless spot weld
repaired, they didn't even charge me as they had just finished a spot
welding job and the equipment was still hot and ready to go.
Paul
Maybe you can just use countersunk backing washers for the rivets.
Then you wouldn't need to worry about countersinking the colander
parts. My guess is that the stainless would take the dimpling without
tearing, but that's my WAG.
In article
,
"Denis G." wrote:
Or use a truss-head rivet for much the same effect.
The SS will surely take the dimpling. The problem is making neat
dimples without the right equipment, and no scrap stock upon which to
experiment.
I've dimpled soft aluminum (Bud boxes) with a flat-head SS screw drawing
the sheet into a countersunk recess in an aluminum block by tightening
the nut on the SS screw. Not clear that this will work with SS, which
is far stronger.
Joe Gwinn
In article
,
" snipped-for-privacy@co> > > A few days ago, a foot broke off of my wife's favorite colander. I was
Yeah, that would have worked too. There must be many SS fabricators
around here (suburbs of Boston).
Joe Gwinn
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