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Spot welding

Posted: Sat Sep 29, 2018 11:42 pm
by Ol'fogasaurus
I have a 120 v spot welder and have tried to use it with not much success... mostly 'cause I don't really know what I am doing.

I am trying to tack two different gauges of steel together in prep for welding one to the other for a spacer (The area I will be welding in is too tight of an area for clamps and I am not ready for drilling holes for bolts. I will then machine the two to make the lower surface of the two to join in a flat surface).

Looking for tips and charts on line they are confusing and only seem to deal with cycle time (per second?) and amount of pressure applied for the clamping/welding time. Is there a better way to do it for this kind of lightweight weld or something to look at when judgeing the clamping time?


Thanks guys.

Re: Spot welding

Posted: Sun Sep 30, 2018 12:35 pm
by Ol'fogasaurus
I've done some searching on the web, looked at some videos and some charts and am somewhat still confused but this video, especially the second one did some clarification for me.

In the second video it shows the melting and welding together of the two pieces of metal. When you see a drawn picture of a spot weld there is a round spot shown... that is the welded/material flowed together shown in the second video.

Other things I read was to clean the top and bottoms of each piece. The first video doesn't necessary show that but it does show the distance between spot welds (look for charts on this. They also show some confusing things [until you understand more] that are important.

I went out this am for a short while (we have company showing up shortly for a short visit so I didn't want to get dirty :roll: ) and did some spot welds (pix later). Again, my spot welder is 120 v vs. the 240 v but should handle what I need to do.

This is what I think I found out:

1) The clamping together of the materials before and after you hit the trigger is important. You want to continue to hold the material tight after releasing the trigger giving the melted metals time to cool off and solidly join.

2) If you hold the trigger long enough for the top and bottom of the material start to melt... you have held the trigger too long. You want the middle of the material to melt and join. Holding it too long can weaken the metal (I got this feeling from the reading I did).

3) The spacing distance between spot welds seems to be of the same spacing importance just like bolt, rivets and other types of joins require.

4) I don't think a single spot weld is quite as strong as a MIG or TIG but no proof of that either. Just a feeling!

I did some gentle pulling, pushing but no yanking or lifting: I wanted to wait until things had cooled off but had to vacate the garage too soon.

The area surrounding the spot weld does get warm so be warned... especially if the button is held too long.


For what it is worth.

Re: Spot welding

Posted: Sun Sep 30, 2018 12:58 pm
by Ol'fogasaurus
My wife was washing clothes so she couldn't hear me sneak out to the garage where I took the pictures.
IMG_1353 copy.jpg
This is the three pieces I tried to weld together. All were scrap so no loss here... I think. The long piece is much thicker than the other two and I think I got the temp pretty close.
IMG_1354 copy.jpg
A close up of the first two spot welds. The one with the red arrow had the trigger pulled too long. The back arrow is closer but still too long. It looks like trial and error is going to be necessary :wink: :lol: .


Re: Spot welding

Posted: Sun Sep 30, 2018 1:59 pm
Having spent a great deal of time, many years ago, Spot welding 18 gauge and 16 gauge galvanized sheet all day... I see no issue with the "Way too long" spot weld, by appearance. You have two different thickness metals, you indicated, so this is to be expected... at least somewhat. Not knowing the whole story and layout and all, since you can't use clamps to get the piece in place, maybe you can use some magnets instead. Magnets are your fiend in this situation as far as I can tell. At least if you're more proficient with another welding type, you have more of a chance to control your HAZ and get the results you want.

Considering the spot welder is a 120 unit, I think your spot welds look fine though. You don't have a 3 phase mega bad ass commercial robot welder there... concessions should be made to allow for the smaller, lower voltage and available current.

Re: Spot welding

Posted: Sun Sep 30, 2018 2:47 pm
by Ol'fogasaurus
Thanks Scott. My magnets are too big for the approx 1X2 area I have to work in.

Good to know what I did was marginably OK shot the first time I seriously tried it.

In the reading I did read about 3-phase and all the things you can add to it but for the small one time (maybe) I might use it, it would be cost prohibitive :lol:

Thanks again.


Re: Spot welding

Posted: Sun Sep 30, 2018 5:55 pm
by Ol'fogasaurus
I did try to break the welds and finally did get the thicker narrow piece to fail but only by lifting it up. The other two welds seem to support each other and were good and tight.

I wonder if a second spot weld would have made a difference on the one that did fail. You could see that the joined metal wasn't as deep as it probably should have been.

This has been a very interesting test.


Re: Spot welding

Posted: Mon Oct 01, 2018 6:34 pm
well... even a GOOD pot weld can be twisted apart... so lifting a piece of metal and it failing sounds like a bad weld. Appearances (online especially) CAN be deceiving sometimes, but they looked do-able to me from your pics. As far as "a second spot weld" on the one I'm not sure if you're saying welding right into the same weld? or a second one nearby.???

Generally speaking, Spot welds depend on design more than a great weld, and are often used instead of seam welds to let metals grow and "move" when attached and other such engineered features. I'm not a welder by trade or anything, but I have seen some spot welds that I thought would just come right apart with a screwdriver wedged between the sheets... require a chisel to cut through the joined metals to separate the sheets. And I've seen some that looked perfect fail without any help whatsoever. HAZ shouldn't be 3 inches around a single Spot weld, but a nickel to a quarter isn't bad on some applications, depending on the two sheets being joined. This especially if one sheet is thicker. This can also be determined by how big the contact points of the welding tips are, and how well they're manicured (Dirty tips make messy welds just like any other welding).

I used 2 types of spot welders one was a Stand up Pedal style unit, the other was a Smaller unit like you have. The smaller one I had to work harder to get good welds, where the Pedal type unit was easy to get good welds due to the leverage Gained from the pedal being 3 feet long.

Re: Spot welding

Posted: Mon Oct 01, 2018 6:52 pm
by Ol'fogasaurus
I pretty much agree. Welding with the proper spacing between welds is very, very similar to the same problems when bolting or riveting things together. They all work together as a unit rather than acting singularly.

The same with holes; proper spacing and, if a second line is added then the offset between the first line of holes and 2 1/2 diameters distances are very critical to strength ( ... ce-547.htm); adding flanging of the holes is just another way of gaining strength.

Oh, and the lifting of the one piece wasn't just a little wimpy lift, I tried to see just where it would fail assuming it would.