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Thread: Improvments to the common spotwelder plans

  1. #1

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    May 2015
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    Improvments to the common spotwelder plans

    So I was thinking about making a spot welder. Very common project to the point KingOfRandom has done it, the youtube channel where ideas go to die.

    I was wondering if anyone who has expierence using spotwelders could suggest relatively simple improvments to the common idea.

    I was thinking about adding a small fan to cool the transformer for a start. Possibly a fan salvaged from the microwave I get the transformer from.

    Guy in the video mentioned a timer. Not quite got the electrical skill to know how to go about that but if someone could explain it that would be nice. If anyone else has ideas to give please bring them.

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  2. #2
    Supporting Member Toolmaker51's Avatar
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    Feb 2016
    Midwest USA
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    Toolmaker51's Tools
    How goes your project?
    I'm interested in this as well. So far, I've collected the outline and things to consider.
    First impression is capacity of a microwave transformer and gauge of metal you'll work with.
    Next is what your electrical service is. Bigger handheld units are 220 single phase. I wouldn't want smaller.
    It also seems like an arc welder with incremental amperage would be a good source of power, build a tool that plugs in.
    Building one, the main task is the squeeze and contact mechanism.
    There is a break in commercially made welders from fan to water cooled, related to power and duty cycle. Water cooling runs a little heat exchanger, a auto heater core size, and jacket is within the arms holding the copper tips.
    At work, ours has a timer sensitive to partial seconds, with a vernier style knob. Newer machines are probably digital.

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  3. #3
    Supporting Member Frank S's Avatar
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    Aug 2015
    Peacock TX
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    Frank S's Tools
    There have been literally 1000s of small light duty spot welders made from salvaged microwave transformers As I say light duty, although many U tube vids boast such claims as 500 to 900 amps output all of those claims are based on faulty data assumptions
    I built 1 of these transformers just to see what it would do for my secondary wire I had 00 ga battery cable since I wasn't planning on completing a spot welder I just crimped a pair of cable ends on it then vice gripped a couple of used mig welder contact tips to them it would spot weld 2 pieces of 24ga metal together but not very fast
    for a good spot welder you could remove the transformer from an ac stick welder retain the primary windings and re wire the secondary winding for a 3 to 5 volt output use the formula of 2 turns per volt with as many in hand parallel wires as will fit.
    to yield the amperage output A simple adjustable core AC stick welder makes the best transformer to use
    For a timer this is also easy buy an octal timing relay and base socket with a 120 or 240v coil depending on your input voltage wiring instructions will be included in the package they come with 20 amp rated contacts but a heavier timing relay with 50 amp contacts will last longer.

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