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  #11  
Old 12-10-2013, 10:03 AM
crystallographic crystallographic is offline
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[QUOTE=Alan83;85883]Okay, I am brand new to welding and metal work in general. Trying to expand my horizons.
I haven't been able to find anything in my searches on this forum to answer my questions, probably because they are ridiculously stupid.

Anyway, below is a description of the problems I'm having.
It was recommended I get a Harbor Freight #45689 hand held 115v spot welder to start, since I'm not welding anything really thick, less than 1/8" total. The manual says it should be good for UP TO 1/8" mild steel.
I can not for the life of me get the thing to make a weld.

Yeah, it turns a bright orange in the area of the tips. It will hold together, sorta. But I can break it apart with a chisel and hammer with relative ease; snaps apart right at the weld.

I've got my tips at tight as I can adjust them.

I've held the power on as long as 8 seconds. (Afraid to hold the power any longer as it can be pretty hard to break the work piece off the tips.)

Oh, almost forgot.
What constitutes "MILD" steel? Anything xx40 or less? xx50 or less?

I've had this problem with my Miller MSW42 over the past decades, and it is always from
1) metal somewhat dirty, so scrub it bright
2) dimple one sheet a little to make a better contact "bump"
3) make sure the tips are flush with the arms - file or dress them with sanding block for best 100% surface contact
4) tips have to be pretty sharp, with maybe a radius of 1/16"
5) you should feel the machine "growl" and not just hum when you hit the trigger, and sparks should fly when the metal goes orange.
6) you may not have tight electrical connections internally - from new - which is not uncommon with the offshore machines. Open up, sigh, and re-tighten.

It is really frustrating to have this happen, and with 2 machines to maintain I know this first hand.
Best luck, success, and joy,
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  #12  
Old 12-10-2013, 12:25 PM
Alan83 Alan83 is offline
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Thanks again to everyone who has posted advice.
I was under the impression that the steel should tear before the weld failed also.
How clean is clean for steel?
I can imagine,now that it has been mentioned that the sheet metal from Lowes may have a shellacky (sic) coating to protect it longer.

So for cleaning.
Acetone for degreasing?
Sanding for removal of more durable coatings? (Primers, shellacs etc...)

Tips:
Should tips be of identical size?
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  #13  
Old 12-10-2013, 12:26 PM
Alan83 Alan83 is offline
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Also, what is considered the dividing line between mild steel and high carbon?
<xx50 mild?
>xx50 not mild?
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Old 12-10-2013, 02:09 PM
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Steve Hamilton Steve Hamilton is offline
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Alan

This thread has a lot of good information. I'll add a little more.

The tip sizes can be different, in fact some times a flat is used on one side to keep the surface flat instead of dimpled.

The size of the smallest tip will determine the size of the weld. A smaller tip size will create a smaller but hotter temp. for the same amperage & time.

Think of it like the size of a wire, smaller size more resistance.

If the tips are removable from the arms check that they are clean & tight. Also check the clamps that hold the arms, for clean & tight. Fine sand paper to remove oxides. Last time I purchased tips I received a small tube of High temp dielectric grease with them, to slow down corrosion. If there is a silicone type grease on the arm clamps or the tips that is probably what it is.

Spot welding is a form of resistance welding. You want the highest resistance at the point of the weld, and low resistance at all other connections.

To clean the tips where they contact the sheet steel I fold a piece of 320 wet or dry sandpaper in half, put it between the tips, just let the weight of the upper arm rest on the paper an slide it pack and forth a few strokes.
This cleans them and makes them parallel.

Try some thin sheet steel and see if it weld correctly, then keep testing thicker to find the equipment limit.


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Old 12-10-2013, 02:50 PM
crystallographic crystallographic is offline
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[QUOTE=Alan83;85927]Thanks again to everyone who has posted advice.
I was under the impression that the steel should tear before the weld failed also.
How clean is clean for steel?

"Clean" means no wax, grease, oil, silicone, varnish, shellac, urethane, acrylic, lacquer, undercoating, or protectant at all.
Naked.
Spotless.

How you get clean is your own process of paint remover, sand blasting, heating, brushing, abrading, sanding, grinding, scrubbing, and then washing with 91% isopropyl, acetone, MEK, lacquer thinner, or other appropriate solvents until you have nothing but the base metal that you wish to weld.
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  #16  
Old 12-10-2013, 03:12 PM
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as a general rule for welding, when you think the area is clean enough to weld! clean some more... i was always told to clean the area by a dry method (no liquid chemicals) as its safer.

quick point of reference, aerosol brake cleaner has a product in it that reacts with the argon in welding gas (obviously not spot welding). a nostril full of this mixed gas can be fatal. there have been reports of this so please be aware!
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  #17  
Old 12-10-2013, 03:50 PM
Leif62 Leif62 is offline
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Neil
the check for welds is as follow: spot weld two
pieces of metal together with one weld. Try to pull the two pieces
apart. A good weld will cause a hole in one piece.
This recommedation is from the manual of my welding machine.
Andreas
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  #18  
Old 12-11-2013, 02:40 AM
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andreas, yes i went through that test procedure at college back in 80's

obviously i will apologise if i took that question the wrong way.
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  #19  
Old 12-11-2013, 11:37 AM
Alan83 Alan83 is offline
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SUCCESS!
This morning I sanded my practice pieces on both sides. I only went with one spot per piece and managed to produce a nice 1/16" diameter hole in the 20ga. piece. (1/16" is indeed the approximate size of the upper tip like Had to anchor one end to my truck while I pulled with a vise grip on the 16ga. piece. Took some doing but I eventually got it to pull apart.

I'll try next for a 1/8" nugget with my larger tip at the top. But I'm thinking I'll have to turn that down at the tip to match the lower. But it is rounded so it may only have about a 1/8" contact anyway. I guess I'll find out. I want to make sure I've got this down before I move on to my project pieces.

Thanks again y'all, you've been most helpful.
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Old 12-11-2013, 08:51 PM
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always nice to hear success
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