DIY resistance welding?

I want to make some small diameter rod racks for spices. I think I'll use 1/4" or less square and round bar. I'm going to twist the round, and
square, making spirals, geometric designs, freehand stuff, then bend it to form the rack. Mainly kitchen spice racks, knife holders, holders for containers, etc.
I have a Lincoln 175 SP+, and can do some HOT spot welds. I don't want to do very much weld metal deposit to keep from warping.
I have been interested in what it takes to put two pieces of bar together, and zap them and melt them like the shopping carts are made. They come up so beautifully fused and even.
Is there a resistance welding device made, or can I do it with just a welding machine with a momentary blast of current? As with CadWelding studs, is there any type of powder available that I can put in the joint that would melt when it arcs?\
Or just keep it simple and tack it hot?
Steve
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Standard spot welder with suitable tips is the way all the racks and grocery carts are put together. The tips for this application are either large flats or flat on one side and grooved on the other.
Not sure about the kw requirement for various wire sizes. I've been meaning to do some quick testing using the 120 volt portable unit out in the lab. Suspect that it will do 1/8" steel wire, not much more. And that 1/4" rod would take a 10kw unit.
On 4/11/2010 11:50 PM, Steve B wrote:

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What's that Lassie? You say that RoyJ fell down the old sci.engr.joining.welding mine and will die if we don't mount a rescue by Mon, 12 Apr 2010 08:22:41 -0500:

I think it might do more. If the wires are crossed at 90deg. there is little contact area until the metal starts to melt. I bet you could do 3/16 - 1/4 good enough for a spice rack.
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Dan H.
northshore MA.
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But how about the on/off? I'm thinking something with long arcs of electricity like in Dr. Frank's lab. Any way you go, there would have to be quite a zap at contact, unless you were using one of the clamp spot welders mentioned.
Steve
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What's that Lassie? You say that Steve B fell down the old sci.engr.joining.welding mine and will die if we don't mount a rescue by Mon, 12 Apr 2010 21:07:04 -0700:

What ???

That is what we are discussing.
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Dan H.
northshore MA.
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Steve B wrote:

Cheaper and easier to buy a twin tong spot welder and make a set of tongs to fit you application. I have one of the HF units and it does a good job on most stuff. It's not as nice as the expensive unit I have but it is easy to take with me when needed.
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"Steve W." wrote:

Which HF model do you have and what's not as nice as the higher end units? I've been thinking of getting the 240V model for my home shop to supplement my other welding gear, not because of any huge spot welding need, but they are not very expensive and I can see one being useful on various projects.
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The 120 volt hand held models are usually rated at 1.5kw, the 240 volt hand held models are usually around 2.5 kw. The stand up commercial units run 10 to 25 kw. Not only is 'bigger is better' but the higher end units have a programmable pulsed mode that lets you warm up the weld site, hit it with the main current, then taper off to get a good weld. The portable units have an 'on-off' and that's it.
I did some pull testing of the welds from our 120 portable unit. Doing a single weld on 18 ga 1/2" wide clean mild steel, about 3second weld time, got consistent ultimate pull strength around 800 pounds. The base metal would tear in a 1/4" circle around the weld nugget. very impressive.
On 4/12/2010 1:17 PM, Pete C. wrote:

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RoyJ wrote:

My primary use for the hand held is body work and thin sheet. Most of the body work is things like drip edge welds, door skins, Trunk lips and the like. Usually a 3 layer crimped sandwich.
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RoyJ wrote:

It sounds like I'd be happy with the 240V unit. The two units seem to be the same size physically and anywhere I might want to use it I can get 240V. I'd be using it for light sheet metal and/or small gauge wire applications.
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One major application is sheet metal duct work on site. 24 and 26 ga galvanized. 120 volt unit works great, don't plan on having suitable 240 outside the shop.
On 4/12/2010 4:16 PM, Pete C. wrote:

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RoyJ wrote:

I don't plan on doing any duct work other than at my house or shop, and 240V is readily available at either location.

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Pete C. wrote:

I have the 240 model from a couple years ago. It works OK but is not as nice as the Miller I have. Replaced the power cord with a better longer unit. Replaced the tong clamping screws with better ones. Some other minor things are the lack of controls. The Miller is adjustable so you can weld faster and use larger points as well.
For probably 90% of spotwelding use IE:sheetmetal on cars and thin sheet items it is fine. Duty cycle isn't that great but unless your doing long term production work it is fine.
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Steve, you need this sort of a welder.
http://yabe.algebra.com/~ichudov/misc/ebay/Peer-Spot-Welder/ebayhist.html
I sold it long ago but it may give you an idea. $70
i

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I got $100 for it IIRC. It was a complete steal both ways. A real production machine, taking very little space.
i
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snipped-for-privacy@dishynail.net says...

I would recommend you look at "Capacitor Discharge Stud Welding."
In the shipyard, we've got stud guns that will shoot virtually anything from an inch in diameter down to the size of a gnat's a$$. Often, these studs are long (3 or more inches) and have a 90 degree bend, so we use "open sided" guns that you can slip on and off the stud without having to disassemble the gun to remove it after the stud is welded.
Cap. Discharge sounds like it will be the way to go for you, especially since you anticipate working on thinner materials. I know a 110 V. box will reliably shoot up to 1/4 in studs if you get it set up just right. A 220 V box should be perfect for your needs, and gives much more flexability.
Cap. Discharge also gives you the flexability of not needing to use specialized studs. Most Drawn-Arc studs use a fluxed stud and a disposable ferrule, which will drive up costs.
I've not personally seen a stud gun built to shoot square stock, but if anyone can jerryrig one, this group can!
You may well be able to modify the gun and ground setup to create a very good spot welder, too.
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TinLizziedl wrote:

The gun I use to tack on pull studs and comb wire can be modified to do spot welds. The catch is that it would cost more for the pieces than it's worth....
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I have to ponder a three-prong grounding clamp. Insulate the screw foot and one of the other legs, leaving a copper contact on the third foot.
Use something like a copper stud in the gun.
What would it cost to mill a piece of copper to provide a snug fit in the gun? To tap a few pieces of copper to fit a small stud on the grounding clamp? This way you have replaceable contacts....
Just a thought-
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Tin Lizzie
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    --Silly question time: do all resistance welders have to have that honkin' big transformer located on the 'handle', or are there ways to get the pulse down a cable from a more remote heavy object?
--
"Steamboat Ed" Haas : Blue Cross socks us
Hacking the Trailing Edge! : $23,000/yr!! ...
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steamer wrote:

Nope. You can build them a lot of ways. Most of the self contained units follow the same design with the transformer at the handle.
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