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Spot-welding .040" 308L CRES SS rod

R

Rich Grise

Jan 1, 1970
0
crossposted to sci.engr.joining.welding and sci.electronics.design
please manage followups intelligently, thanks.

I've fashioned sort of a paper catcher for my Canon printer, with
..040 TIG filler rod and duct tape. So I thought it'd be cool to
spot-weld it, and so I STFW spotwelders and realized I have a
scrap microwave oven (I don't know if it works or not, but
I have two others anyway) and access to a machine shop, so I'm
contemplating what it would take to make one. I have in mind
something on the order of a fat pliers, but insulated. I can
get "glass pliers" at McMaster-Carr,
http://www.mcmaster.com/asp/DisplCt...A71&t1=PN&ScreenWidth=1600&McMMainWidth=1019#.
[wrapped terribly - please cut'n'paste]

but I wonder what kind of temp. they'd stand up to - alternatively,
does anyone know of either something like that that would handle
high temperatures, or from experience, tell me not to worry
because the electrode holders only get up to XXX deg. C or
something. I've worked with "Garolite," which is basically
phenolic - very nice to machine with, but it scorches. But
maybe a couple of lumps of copper wouldn't get too hot doing
..040 steel wire at 4VRMS.

And, if anybody's done that before, (.040" dia. 308L SS), what
kind of amps could I expect? They recommend #4 wire, so I
expect maybe close to 100. (hmmm - how many amps does it
put out at maggie voltages? How many watts was the oven?
Ah, that's it.) 750W @4V = 187.5A. Hm. But for a very short
period of time, and that's assuming superconducting 308.
I guess I should just do it, and borrow an amprobe. Or
watch the joint.

So, can anybody recommend either glass-filled epoxy, garolite,
or something else for an electrode holder? And is brass better
than copper for the electrodes, because it's harder?

Thanks!
Rich
 
T

Tim Wescott

Jan 1, 1970
0
Rich said:
crossposted to sci.engr.joining.welding and sci.electronics.design
please manage followups intelligently, thanks.

I've fashioned sort of a paper catcher for my Canon printer, with
.040 TIG filler rod and duct tape. So I thought it'd be cool to
spot-weld it, and so I STFW spotwelders and realized I have a
scrap microwave oven (I don't know if it works or not, but
I have two others anyway) and access to a machine shop, so I'm
contemplating what it would take to make one. I have in mind
something on the order of a fat pliers, but insulated. I can
get "glass pliers" at McMaster-Carr,
http://www.mcmaster.com/asp/DisplCt...A71&t1=PN&ScreenWidth=1600&McMMainWidth=1019#.
[wrapped terribly - please cut'n'paste]

but I wonder what kind of temp. they'd stand up to - alternatively,
does anyone know of either something like that that would handle
high temperatures, or from experience, tell me not to worry
because the electrode holders only get up to XXX deg. C or
something. I've worked with "Garolite," which is basically
phenolic - very nice to machine with, but it scorches. But
maybe a couple of lumps of copper wouldn't get too hot doing
.040 steel wire at 4VRMS.

And, if anybody's done that before, (.040" dia. 308L SS), what
kind of amps could I expect? They recommend #4 wire, so I
expect maybe close to 100. (hmmm - how many amps does it
put out at maggie voltages? How many watts was the oven?
Ah, that's it.) 750W @4V = 187.5A. Hm. But for a very short
period of time, and that's assuming superconducting 308.
I guess I should just do it, and borrow an amprobe. Or
watch the joint.

So, can anybody recommend either glass-filled epoxy, garolite,
or something else for an electrode holder? And is brass better
than copper for the electrodes, because it's harder?

Thanks!
Rich

Magnetron want high voltage at (relatively) low current, so while the
transformer core may be worth while to you nothing else will be. To get
the high-current low voltage source that you want you'd need to rewind
the thing.

The one spot welder I worked with had copper electrodes, and they didn't
get that hot -- the point of resistance welding is that the highest
resistance point should be the spot that you want welded. Since you're
trying to weld stainless this part should be easy. Copper is both
highly conductive and tends to conform to the part that you're clamping to.

If you want to weld stainless you will need to have some sort of a
neutral atmosphere or a flux. You used to be able to get stainless
welding flux, but I don't know if anybody bothers with it anymore.
 
T

Ted Edwards

Jan 1, 1970
0
Rich said:
I've fashioned sort of a paper catcher for my Canon printer, with
.040 TIG filler rod and duct tape. So I thought it'd be cool to
spot-weld it,

Do you have a TIG welder as well as the filler? If so just gently tack
it without additional filler.

Ted
 
R

Rich Grise

Jan 1, 1970
0
Tim Wescott said:
Rich Grise wrote:

Magnetron want high voltage at (relatively) low current, so while the
transformer core may be worth while to you nothing else will be. To get
the high-current low voltage source that you want you'd need to rewind
the thing.

Oh, yeah - that's one of the "easy" parts - cut off the secondary, wind
a few-turn secondary of hookup wire, that'll give turns/volt; then wind
enough #4 or so to make 4V.
The one spot welder I worked with had copper electrodes, and they didn't
get that hot -- the point of resistance welding is that the highest
resistance point should be the spot that you want welded. Since you're
trying to weld stainless this part should be easy. Copper is both
highly conductive and tends to conform to the part that you're clamping
to.

These are a couple of good points. I have to keep reminding myself
that copper is, after all, metal, and not wax or modeling clay. ;-)
If you want to weld stainless you will need to have some sort of a
neutral atmosphere or a flux. You used to be able to get stainless
welding flux, but I don't know if anybody bothers with it anymore.

I'm sure I could get flux at the local weld place; inert gases are
no problem because I live in a weld shop. :) But it'd be a PITA
if I had to depend on the company's gases to do personal projects.

Thanks!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Ted Edwards said:
Do you have a TIG welder as well as the filler? If so just gently tack
it without additional filler.

Ted
What kind of amps and volts would you dial in? We have a TIG (or two
or three), but I don't know if the owner would want me to play with
it/them. I can make a puddle, but the (first and) last time I did it
I melted the guy's tungsten. Luckily, I had read about grinding a
new point, so that turned out OK, but I'd need a good coach. I've
OA brazed mild steel, with coaching, and I've FCAW'd - at least
one item with my welds lasted almost 10 years that I know of, and
another was still in service 6 mos after I left that company. It
must be butt-easy. ;-)

Thanks,
Rich
 
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