Spot welding

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gamble
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Spot welding

Post by gamble » Fri Aug 28, 2015 10:58 am

Anyone here spot weld a lot? I picked up an el cheapo HF spot welder for the purpose of putting brackets on most of my pieces to hang them.

The electrodes are flat at the end and tent to leave a little divot in the metal. I remember using spot welders at work with a rounded electrode (and a lot more expensive) and they didn't leave an indent in the material. You think this would help using a rounded electrode? Not that anyone makes them, so I'd have to make my own :(
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Mtw fdu
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Re: Spot welding

Post by Mtw fdu » Sat Aug 29, 2015 3:01 am

I use a spot welder every so often and it is supposed to leave a small divot in the metal.

If you can also see on where cars are spot welded together...there is always a mark it leaves.

I have my tips small (about 3mm) round and with some primer it covers them up quite nicely. You have to look very closely to see the mark it leaves sometimes.

Is there a problem with them being seen???

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acourtjester
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Re: Spot welding

Post by acourtjester » Sat Aug 29, 2015 8:42 am

The process of spot welding is to super heat the 2 metal parts to fuse them together. The clamping action of the tips is what makes the marks in the softened metal surface. I have not tried this but may be if you had a larger diameter tip on the side you don’t want to mark it would have a larger contact area there. This may not cause that surface to squash in as much only the back side with the smaller tip. Simple test flatten a small piece of copper pipe and put under the tip on the side of the metal you don’t want marked and spot weld it to see. One time should tell you if it works.
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gamble
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Re: Spot welding

Post by gamble » Sat Aug 29, 2015 10:59 am

Mtw fdu wrote:I use a spot welder every so often and it is supposed to leave a small divot in the metal.

If you can also see on where cars are spot welded together...there is always a mark it leaves.

I have my tips small (about 3mm) round and with some primer it covers them up quite nicely. You have to look very closely to see the mark it leaves sometimes.

Is there a problem with them being seen???

Mtw fdu.
It's a huge problem seeing them. They are such an eye sore. Even when I grind them flush and paint over it you can still see grind marks.
acourtjester wrote:The process of spot welding is to super heat the 2 metal parts to fuse them together. The clamping action of the tips is what makes the marks in the softened metal surface. I have not tried this but may be if you had a larger diameter tip on the side you don’t want to mark it would have a larger contact area there. This may not cause that surface to squash in as much only the back side with the smaller tip. Simple test flatten a small piece of copper pipe and put under the tip on the side of the metal you don’t want marked and spot weld it to see. One time should tell you if it works.
Not a bad idea. I'll have to see if i can find two rounded pieces of copper to play with
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acourtjester
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Re: Spot welding

Post by acourtjester » Sat Aug 29, 2015 2:16 pm

Gamble you don't want to go too big on the top contact as it will change the concentration of the heat effected area.
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Mtw fdu
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Re: Spot welding

Post by Mtw fdu » Sun Aug 30, 2015 4:13 am

Here is a quick pic I took of the spot welds I have doe on my table.

You can see them because there is dust collected in them. Hope it shows how small they are.

Mtw fdu.

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Re: Spot welding

Post by motoguy » Tue Apr 05, 2016 3:20 pm

Did the copper spacer/flattened tube on the front of the weld help with the visible mark?
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plasma_burn
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Re: Spot welding

Post by plasma_burn » Tue Apr 05, 2016 5:32 pm

I have a similar problem, from another forum
http://www.practicalmachinist.com/vb/fa ... on-131924/

references a Miller spot welder manual that has different tips including a flat tip
http://www.millerwelds.com/pdf/spec_sheets/SW1-0.pdf

the guy on the other forum said the flat tip worked.

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tinspark
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Re: Spot welding

Post by tinspark » Tue Aug 20, 2019 3:50 am

Use a piece of aluminum (.063)on the side that you want to finish. (old tinners trick)!!
Typically the lower spot welder tongs will contact the non- finished side. Lay a small piece of aluminum on the top (finished) side and then spot weld as you normally would. A little bit of the aluminum may remain on the spot welded material, but you will notice the spot weld is convexed instead of concaved. This will pull the divot up instead of leaving a crater. Use an angle grinder to sand to flush. all of the aluminum as s\well as the raised base metal should be flat. Works great on stainless too.

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cuttinparts
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Re: Spot welding

Post by cuttinparts » Tue Aug 20, 2019 10:18 am

tinspark wrote:
Tue Aug 20, 2019 3:50 am
Use a piece of aluminum (.063)on the side that you want to finish. (old tinners trick)!!
Typically the lower spot welder tongs will contact the non- finished side. Lay a small piece of aluminum on the top (finished) side and then spot weld as you normally would. A little bit of the aluminum may remain on the spot welded material, but you will notice the spot weld is convexed instead of concaved. This will pull the divot up instead of leaving a crater. Use an angle grinder to sand to flush. all of the aluminum as s\well as the raised base metal should be flat. Works great on stainless too.

Regards,
Great tip, gotta try that! Thanks :Like

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