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MG Midget and Sprite Technical - Plug welding problem

I've been attempting to plug weld the steel strip shown in the picture to the edge of the Frogeye rear shroud. Underlying metal was cleaned with a 40 grit flap disc and the strip clamped to the shroud. Good earth. Welder is a Murex Tradesmig previously working properly. Gas is CO2/Argon set at 10l/min. Welder set at 3 or 4 out of 8 corresponding to 70 / 90 amps. I pointed the torch at the centre of each hole and spiralled out with a nice sizzle and red hot bead. EVERY weld failed to penetrate resulting in holes full of weld but no attached welds. What might I be doing wrong?
Bill

W Bretherton

Bill,

Can you provide a close-up shot of a failed weld as the image you posted didn't tell me anything.
David Billington

what did you attach the welder earth clamp to - think it works best if it's on the shroud, not on the strip or one of the attachment clamps.
David Smith

What sized plug holes are you using? It's clearly establishing an arc to the edge of the hole in the top sheet rather than the steel in the wing beneath. Where is your earth lead connected?
GuyW

Personally l find the little holes that those joddler punches make are too small for my unsteady hand. Bigger holes are easier as the arc needs to strike on the unpunched sheet first, and to build up a weld pool in the centre before finishing with the little spiral movement. Try experimenting on scrap first. You may need to reduce the wire feed speed and possibly try a slight increase in the current but not so much that you blow holes in it!
GuyW

I agree with Guy. The holes made by a joddler never worked for me either. IIRC I drilled 8mm holes and got on much better.
Mike Howlett

Another vote for 8mm minimum. Any smaller doesn't work. Weld settings etc. sound good to me.

Malc.
Malcolm Le Chevalier

David B, I've just attempted two more pictures from both sides. The first shows the weld in the holes,the second pointing to the underside where no penetration is evident. Best I can do at the moment as the strip is attached by a couple of tacks.

David S
Earth clamped to shroud.

Guy
Holes were initially joggler 5mm but I drilled them to 6mm. Should I go 8mm say? As you suggest, I was thinking the arc is striking sideways to the top sheet which is no good of course. I'll try bigger holes. Wire feed is slow. I tried heat setting 4 out of 8 which, on a 160 amp welder, must be around 90 / 100amps - you'd think that would blow a hole in 1mm or so metal.

A problem I find is that, holding the torch vertically over the holes, you can't see what you're doing and my auto darkening helmet is pretty dark but I'm wary of turning it down. Thanks everyone, I'm beginning to think I can't weld.......
Bill

W Bretherton

And the underside

W Bretherton

Mike/ Malcolm
Yes, that makes sense, thanks. I assumed the torch would blast the arc to the lower panel but it clearly doesn't. Harder than you think to get it right.
W Bretherton

Yeah, looks like your holes are a bit small, you strike on the edge, get a small bit of sizzle but no real penetration through to the base metal.

Making sure the workpiece is well lit is helpful. When welding in the dark, you can struggle to see even with the light of the arc, stick a lamp on it and you can see fine.

I don't want to intrude, but I am free next week if you want a hand? I can't claim to be a pro, but I have done a fair bit of bodywork and it hasn't snapped in half yet! :-)

90 amp is a fair whack. My welder only goes up to 90 and I rarely use it on full blast for body work.

Stick at it, practice makes perfect.
Malcolm Le Chevalier

Bill,
I don't know if you have discovered this web site but I find it really helpful
http://www.mig-welding.co.uk/plug-weld.htm
GuyW

Thanks for the offer Malcolm, much appreciated. I'm away Monday to Wednesday and busy Thursday but Friday morning is possible? Or I'll give it another go and get back to you.

Guy, yes I read that website, but thanks. I find welding harder than everything else.
Bill
W Bretherton

What size wire are you guys using?

Malc?

Guy?

I'm using 23 gage wire and it seems to be working fine on the front fenders?

Just wondering...sorry to butt in.
S

Steve

I'm using 0.6 mm for panels which is 23 gauge so same as you.

Bill
W Bretherton

Yes, 0.6mm
GuyW

Thanks! I have 30 loaded in my welder...

I borrowed my buddies welder today and his is using 23...

Put some patches in

Way better results with his machine

I've got to convert mine over.

S

My advice, having only just started welding stuff together,is MORE POWER! Turn it up till you can burn a hole in it, then weld so it doesn't burn a hole. No idea if that's right but seems to work for me.
Rob Armstrong

I endorse the comment about good light. Shine a bright light at the work so you can see properly through the helmet before you strike the arc. You will get there. I have a cheapo Machine Mart 100 amp MIG welder and I thought it was rubbish 'cos I kept making such a mess. Then an experienced pal came round and made perfect welds first time using my machine. Practice, practice, and remember, the wire speed makes almost as much difference as the amperage. Oh, and I used 0.6mm wire too.
Mike Howlett

Another vote for 0.6 mm wire.
Malcolm Le Chevalier

Somewhere I read that the wire feeding the wire into the weld pool acts like a conveyor belt carrying the power in faster or slower depending on its speed. I doubt it makes technical sense but to me it was a good way of visualising what is going on and it does seem to give a sort of fine control of the power.

I think when it builds up those little castles of weld and crud it is that the wire feed is too slow and the arc point works its way back up towards the torch tip, building the turd as it does so instead of arcing to the steel. Increasing the wire speed should prevent this and allow the heat to transfer and penetrate the backing steel. If it then blows a hole you need to reduce the power a fraction or if its on an edge that is burning away then try very rapid short pulses of the trigger.
GuyW

Bill,

You may find a MIG spot welding shroud of use to get a better view, plenty on ebay just search for "MIG spot shroud"

With regards turning down the shade level on your helmet you should be fine as they're supposed to provide full UV and IR protection even when undarkened.

As others have mentioned getting some more light in there should help. I have a 150W halogen spot on a magnetic base for such situations. You may be having problems with your helmet also, I had one where I couldn't see the weld area well even outside on a bright day when darkened so I went to using my old fixed shade 10EW filter and I could see the weld area before striking the arc and could see it clearly when the arc was struck so carried on with the job with the old tech.
David Billington

Thanks for the additional suggestions. Is there not a risk of arc-eye with low darkness setting? The spot welding shroud sounds good.
Bill
W Bretherton

Bill,

Arc eye is caused by the UV and the helmet should provide full UV and IR protection even when not darkened. Have a look here http://www.lincolnelectric.com/en-gb/support/welding-solutions/Pages/helmets-eye-protection-detail.aspx
David Billington

Bill,

Had exactly the same problem with plug-welds during the restoration of our Minor bodyshell using the 'joddler' holes and 0.6mm wire. I found that more amps (~90/100A), less wirefeed and a larger hole (~8mm) to plug weld through gave a very consistent result.

The link earlier confirms the hole size and shows that a 'good' plug weld should be flat with the upper piece of material and need minimal dressing - easier to write than to do!

I set my 'auto' helmet to ~10 for thin sheet work and a bit more for heavier work - never had any problem with arc-eye.

Richard
Richard Wale

Thanks Richard, that's useful information.
Bill
W Bretherton

W Bretherton

Just wanted to thank you for posting your question...

I was just getting started on some welding and your question helped me get things set up correctly.

Nice job and let us all know how things turn out.


S

Thanks. I'm away for a few days so will get back to it asap.
Bill
W Bretherton

This thread was discussed between 02/09/2016 and 05/09/2016

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