Tips on using a HF spot welder?

[myredracer]

Have a new HF 240 volt spot welder I want to use on a car restoration. Doesn't seem to be a whole lot of info. around on using a portable spot welder.

Seems like you pull the trigger for in the range of 1/2 to 2 seconds. Some spot welders (fancier ones I guess) use a timer. I can do some testing on a few coupons. Is it as easy as just making sure the welds on the test pieces don't pull apart? Is the timing critical? What about welding 3 layers of sheet metal. Weld two together first, then the 3rd piece or all 3 at once?

The arms aren't parallel. Does it matter if the tip surfaces aren't parallel? Someone on the internet sells an arm that would make the tips parallel or I could make one I guess.

What about pressure between the tips? How do you determine what is right without getting a force gauge? How important is that? Maybe there's the right combo of time + pressure to get a good weld?

I have a picture in my mind of eventually driving down the street one day and having body panels falling off so I want to make sure the spot welds are all good.

 

[txvwnut]

The tips should line up and there should be a way to adjust them. As for how long or how much pressure you are correct in getting some test metal and making a few test spots to see how it will function.

 

[oldtools]

There are tons of Youtube video on HF spot welder.

 

[HMCFab9]

The arms ( tips) NEED to be aligned perfectly, or it doesn't work.
The tips need to be cleaned / filed fairly often to keep it working decent.
Welding 3 layers together doesn't work well.

I'm doing a GTO for a guy.....& he bought the H.F. one. It kinda works, but not the greatest.
After you do the welds, try to pry them apart to make sure you buzzed it long enough.

 

[sevt_chevelle]

As someone who works in the collision industry and has used some high dollar spot welders, the tips NEED to be aligned and clean. Time and pressure matter greatly. The professional units use pneumatic rams to generate pressure levels that measure in the tons, your hand held unit wont even come close to generating the optimal pressure.

I highly doubt any hand held unit has enough power to spot weld 3 pieces together.

You will need to do some destructive testing on some sample pieces. The easiest way is to weld two pieces together leaving enough on each end to able to grab. Take one end and put it in a vise, grab the other end with some vise grips and rotate it back and forth til the weld fails. The weld nugget SHOULD remain intact on one of the pieces of metal, the other piece should have a hole ripped in it.

Depending on amps, time, metal thickness and pressure the hole should be at least 3mm in diameter to provide a good weld.

http://www.slideshare.net/caincastillo94/spot-welding-guidelines Check out page 4

http://mgh-images.s3.amazonaws.com/9780133151213/12385-31-36IQP1.png

 

[myredracer]

As someone who works in the collision industry and has used some high dollar spot welders, the tips NEED to be aligned and clean. Time and pressure matter greatly. The professional units use pneumatic rams to generate pressure levels that measure in the tons, your hand held unit wont even come close to generating the optimal pressure.

I highly doubt any hand held unit has enough power to spot weld 3 pieces together.

You will need to do some destructive testing on some sample pieces. The easiest way is to weld two pieces together leaving enough on each end to able to grab. Take one end and put it in a vise, grab the other end with some vise grips and rotate it back and forth til the weld fails. The weld nugget SHOULD remain intact on one of the pieces of metal, the other piece should have a hole ripped in it.

Depending on amps, time, metal thickness and pressure the hole should be at least 3mm in diameter to provide a good weld.

http://www.slideshare.net/caincastillo94/spot-welding-guidelines Check out page 4

http://mgh-images.s3.amazonaws.com/9780133151213/12385-31-36IQP1.png

Thx, that's the kind of info. I'm looking for. So I'd be looking for more pressure rather than just enough to hold the pieces together? I wonder if it would be worthwhile to make up an adjustable delay-off timer of some sort to help make consistent welds? The HF tips are maybe only about 1 mm across and will have to file them down a bit.

The few Youtube vids on HF spot welders that came up weren't of much value. A guy in one of the videos thought you need to keep energized for 5 seconds. Didn't take him long to figure out that's way too long...

 

[2oolhound]

The time variance will depend on the thickness and type of metal you are using. 2 seconds will burn a hole through thin metal. Your metal must be absolutely clean of any paint or foreign material.

Lots of practice makes perfect!

An added benefit to spot welders is their ability to weld stainless steel together.

 

[sevt_chevelle]

Your HF unit will only produce so many lbs of clamping force no way to increase it.

You need to make up some test samples and find out what your time limit will need to be which will be based off the metal thickness.

 

[kabinenroller]

With that style welder the best way to get good results is to clamp the material together with C clamps or Vise Grip then use the welder to fuse the material together, don't rely on the jaws of the welder to hold the material together.
I have a Lenco welder that has cables instead of jaws,it works very well in areas that jaws will not fit or in one sided welding applications.
It has no amp adjustment, the welder is controlled by a preset timer.
I have found that pre clamping the material yields much better results. The welds look exactly like a factory produced weld.