Spot welder question

I brought home a 5 kVa "Peer" spot welder. This is a stationary standup kind of spot welder, weighs about 250 lbs, and has a
pedal. When I depress the pedal, the top electrode moves down, pushes the parts together, and then current is released as the pedal is depressed further.
I tried it last night, it seems to work, but I do not know just how long to depress the pedal. Would you say that when parts become bright red near the spot, it is enough current for the "weld nugget" to form, or is there some better approach than that?
i
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Ignoramus18803 wrote:


http://www.youtube.com/watch?v=GB0IBOMHhus&feature=related

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--Winston
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Rats. You Tube is blocked at work ...for some reason!
So, how do you like that spot welder? Does it have lots of applications?

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Has that girl got a set of strong hands and good timing, or what? Too bad she's doing that for a living. Looks like a pretty loose operation.
Steve
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Gotta love the open toed OSHA approved third world work sandals as well as the Nomex burka- suit thingie and invisible safety glasses. That chick can move to weld! I bet she has a brand-new camel parked outside and her boss just pulled the AK-47 away from her skull for a hash break. See what .30 cents a week in labor gets you!
Rob
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We did a series of pull tests from a 1.5 kva spot welder using 18ga, 20 ga, and 22ga bare steel coupons with varying times. On that unit, it takes about 2 to 3 seconds to form a clear red nugget depending on the thickness of the material. We found that the pull strength was highly variable when you tried to decrease the time below the red nugget stage, was quite uniform above that point. Net: figure the time for the weld area to get clearly bright red, then add in a safety factor of perhaps 20% in time.
Excessive time brings the weld to orange then yellow. This does not add any strength to the weld, it merely burns the tips out quickly.
Tip life is a function of pressure and material. Too little pressure and the tips tend to arc. Too much pressure and the tips deform. Oily or dirty material likes a bit more pressure to ensue a clean contact. The contact needs to be between the materials as well as between the tips and the materials.
Ignoramus18803 wrote:

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Roy, this was a most useful post. I saved it in my archive. Thanks a lot.
i
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Wouldn't do much for the material-material contact, but I could see a widget on the electrodes that would give 'em just a little 'twist' as pressure is applied to cut through any crud.
Dave
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Many years ago we had a giant 3 phase spot welder. It worked like the one you described, except it had a simple timer to time the weld. You just pulled the handle, and watched the sparks. We used it to weld rods together to make guards. It would sink one rod 1/2 way into the other when set right. Just remembered, you also set the pressure at the tips. Just a spring setup with a threaded rod a nut, and a simple scale. If I remember correctly, when you pulled the handle to squeeze the electrodes, at the preset pressure an arm flipped up into a microswitch. That started the timer. The actual weld time was very short, my guess is less than a second.
Al

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It's all in the wrist... I watch until the area beneath the tips is medium/bright red. Also, you can see the tips 'sink' into the spot as the material goes from hard to semi molten. The best method for you is to gain experience with your unit by experimentation. You can't compare weld times between different units; Too many variables. Use it, and you will learn what different materials and gauges take. Also, on a critical part, do a couple on scrap first, to make sure you are on it. JR Dweller in the cellar
Ignoramus18803 wrote:

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