Spot welding

[Mark69]

Using spot welder this afternoon on rear valence. Spray painted all flanges with weld thru primer. Doesn't seem to weld as good with primer.

Sould I be using this type of primer with a spot welder.

Mark.

[RogerH]

Hi Mark,

if you use a weld through primer you need to keep it on the very thin side.

 

I managed it on my sill last winter.

What sort of diameter are your electordes. Mine from new were like needles. I dressed these to about 6mm da.

 

TRy and get thinned paint onto the joint after welding to allow it to get sucked on by capillary action.

When dry paint/protect as normal

 

Roger

[Motorsport Mickey]

Yes.

 

Mick Richards

[John Morrison]

Hi Mark,

 

I too am fairly new to spot welding,

found that cleaning everything as bright as possible, and then only using

weld thru primer on the inside i.e.mating flanges worked really well.

Initially had primed both sides of each flange and that was a no no.

 

John.

[Mark69]

Electrodes and arms have seen better days I have ordered new ones.

The ones I used today have been dressed to about 5mm. Works well on untreated metal .

 

I will wait and see what results I get with new ones.

thanks Mark

[Mark69]

Hi John

I have treated all sides maybe that's my problem, I'll give cleaning the outer ago

Thanks Mark

[boxofbits]

It's worth ensuring that you are using a good quality weld-thru primer.

 

I used a Halfords brand and it was absolute trash. It sparked and sputtered and was really hit and miss.

 

I just I took it off and used a good quality 3M zinc based weld-thru and it worked perfectly. Lesson learnt.

[SeanF]

Hi Mark,

 

I borrowed a spot welder a while ago and the chap who loaned it to me told me that I should not use any weld through primer with a spot welder. He said that following welding he wicked thinned down primer down into the joints. However, to me life is too short to do that and I have had good success using the spot welder with a thin coat of weld thru primer on the mating faces only. Both outer faces need to be bright shiny metal for it to work best.

 

Sean

[boxofbits]

Agree with that. BMC spot welded most of their cars up without primer and many ended up in a scrap yard within a few years.

 

Kevin

Edited November 13, 2016 by boxofbits

[ed_h]

Hi, Mark.

 

I believe that weld-through primer was originally intended for spot welding, and that is its best use.

 

I agree with others that you could try a different brand.

 

I'd also check your clamp pressure. If it is adjustable, crank it up. A good spot weld requires close contact of the pieces to be welded right at the weld site.

 

Ed

[Mark69]

Thanks for all replys Guys,

Had another go tonight, removed primer from outside of flanges.

Redressed electrodes and cleaned all contact areas on the arms.

Worked a treat.

Managed to weld in rear deck and trial fit wings valence and boot lid.

Pleased with results

Mark

Edited April 14, 2020 by Mark69

[John Morrison]

Way you go Mark!

John.

[SeanF]

Looking good Mark

[Steve T]

I'm spotting using 5mm regularly dressed electrodes on 4 bright sides. Once welded, I'm spraying zinc rich primer into the joints. Seems good so far ????????

[stuart]

As stated you only need a thin spray of weld thru primer between, I use the 3M aerosol type and dress the tips often as if you look at original spots they are very small.

One thing you do need to check when using a spot welder is your voltage at the plug as you will often find that you will get better welds during the day when you dont have lights/electric cooker and all the other household items running indoors when your trying to weld in the garage. Spot welders are very susceptible to low voltage.

Stuart.