I would like to know good/bad in's/out's on anybody that has one. Or any other brands. Anything you guys got on the subject. Thanks in advance

I recently purchased two Miller spotwelders thru an auction Miller LMSW-52 with the timer, they are a 220 volt unit that work excellent with two new pieces of stock similiar thickness. But I am not overly impressed with the results of old sheetmetal to the new replacement metal panels. Cleanliness is always very critical with spot welding and I do not think that can be achieved very easily in restoring an old car. If you just want to duplicate the look of a spot weld, it works great for that.

Most shops I know of that have purchased spot welders have went with pro spot units. May be others that are just as good.
http://prospot.com/products/
Matt

I have the same Miller spot welder, yes cleanliness and flatness of the 2 joining surfaces is extremely important, I usually sand blast the older metal for the best penetration, another thing to consider is your power source amperage supply? the length of any extension cords being used?,these can contribute to poor penetration as well

My buddy used to have a body shop.He had an old Snap On I think that took a welding rod.Then you put the base of the welder on the metal pressed down and a nice spot weld.How heavy etc depended on how long and hard you pressed.The thing was old and that was like 25 years ago but it worked great.Rocky

Liquid cooled electrodes is the best but not necessary for the average hobbyist. I have one that I bought on a deal but it has some serious arcing going on where its not supposed to. Miller is a good brand. Tim

My understanding after a lot of research is,

Duplicating the factory spot welds on older vehicles is all but impossible. one can get the "puddle" but the integrity of the joint may not be there. The newer "body shop" machines are typically designed for thinner metals. Throw in the access issue, IE: getting to difficult areas and getting adequate heat and penetration only Muddy's the waters.
The equipment used on the line was running off industrial amperage / voltage and the individual welders at each station were designed to do a specific job.
Achieving the "look" is one thing, achieving the structural integrity is another.
my research indicated that one is better off structurally to use a mig or tig and do plug welds,

hope this helps