Novice blowing holes in old metal

[dave h 2]

I learned mig welding on an old car I was rebuilding. It was a steep learning curve, and wasted lots of time and effort. I should have done as everybody says here, practise on the bench.

And don't be afraid to adjust your settings either. I laboured on for ages with too much wire speed, for some reason I can't even remember now.

Did anyone else find that settings for bench practise seem different when on a vehicle.

 

[Pigeon_Droppings2]

I'm struggling to see the weld line.

If you haven't got one then get a true colour welding mask...way way better than the green screens.

My eyes are terrible so I have an led lamp in my left hand whenever I'm doing butt welds.

I think when you're beginning there's also tendancy to hold the torch too far away....inner arches are a pig of a job though because you tend to get the mask caught up on the arch!

 

[MGnuts]

I would
Bin the magnets.
Run the welder as low as it will go
Aim at the gap, starting on the new and draging over to the old is like a mini seam weld and too hot for too long. Pulling the gun is cooler than pushing it
Shorten the tack to a really quick bzzt and keep tacking for the whole job as above.
The copper pipe trick suggested works well with contact to flat steel, it won't without grinding all the pigeon pooh weld off the back first. Blowlamping the copper to red hot will make it easier to flatten and form the curve you want.
You can fill a hole by breaking all the welding rules. Lay the gun flat and aim the wire at the thicker weld and build it sideways across the hole to the thin side, again using short tacks allow to cool by doing another one somewhere else, then go back and forth between them.
The quality of 1953 steel may be poor and the cause of some of the problem, after all sweet rationing only ended in 53.

Dave, you make some really good points here and some suggestions as to how I can get out of the mess that I have created. I know I need more practice but there is something different about the 1953 steel as I get a good sizzle noise from welding on the new steel and the moment I hit the old steel this turns to a phutt sound, some sparks and very quickly a hole. The old steel seems solid enough before I weld. Perhaps post war there was a higher carbon content in the old steel?

 

[MGnuts]

I learned mig welding on an old car I was rebuilding. It was a steep learning curve, and wasted lots of time and effort. I should have done as everybody says here, practise on the bench.

And don't be afraid to adjust your settings either. I laboured on for ages with too much wire speed, for some reason I can't even remember now.

Thanks Morrisman, it is very tempting when learning to get impatient with bench practice and switch to working on the car but I'm learning that's just a waste of time and risks damaging the car!

 

[MGnuts]

Try and put more of the heat towards the new steel. If the Autoweld 140 has similar specs to my Migatronic Rally 166 then it is very good for this type of work, I can't seem to find what welder you mean exactly. I am usually doing 0.95mm, if the steel is in good condition then I normally use the #2 voltage setting, if the steel is a bit thin then #1 is used. If your steel is 1.2mm you will probably need to be on voltage #2 or #3, the chart on my welder seems to be pretty accurate. These settings are assuming your Migatronic is very similar, it would be best to reference the chart and higher current is needed for doing spots than if it was a continuous bead. Migatronic originally started to make welders for repairing cars so they are designed for sheet metal and have low minimum currents which are too low for 1.2mm so it is unlikely that you will need voltage #1.

Hi Jack, my Autoweld 140 was probably made in the 1980's but I have a manual and I'm following the chart in the manual, also I'm an electronics engineer so I have checked over operation of the electrics against the circuit diagram which is in the manual. Electrically it seems ok and is unmodified other than having had the rectifier replaced at some time so I think it is working correctly. I am welding on voltage #2, sometimes #3 but #1 is too low and I can't get a good sizzle sound on this setting with 1.2mm. I didn't mention previously but I'm using 0.6mm wire. I will follow you recommendation and try to keep heat toward the new steel.

 

[MGnuts]

If you haven't got one then get a true colour welding mask...way way better than the green screens.

My eyes are terrible so I have an led lamp in my left hand whenever I'm doing butt welds.

I think when you're beginning there's also tendancy to hold the torch too far away....inner arches are a pig of a job though because you tend to get the mask caught up on the arch!

Great tip about the colour welding mask, I'll look out for one. I hit 65 last month so I'm sure the old eyes and what they used to be, I'm not sure I'd be up to holding a LED torch in one hand while welding with the other but I will give it a go!

 

[MGnuts]

Are you spot welding? I’m not an experienced welder but I follow quite a few guys on you tube who restore old cars, most of them are welding in new metal by doing a series of spot welds which join up to become a continous weld which is then ground back to make an invisible repair, by doing that there’s not too much heat being introduced to the metal so it won’t blow holes.
Use an air line if you have one to cool the metal between welds again to keep the heat down and prevent distortion of the metal.

Hi Avi_8, yes this is what I'm trying to do, using a mig welder starting with a series of tacks around the edge then filling in between them moving around the patch to distribute the heat but as you can see my technique is serioualy lacking! It's a shame really because I was very proud of the patch that I had fabricated!

 

[AVI_8]

Hi Avi_8, yes this is what I'm trying to do, using a mig welder starting with a series of tacks around the edge then filling in between them moving around the patch to distribute the heat but as you can see my technique is serioualy lacking! It's a shame really because I was very proud of the patch that I had fabricated!

Your original post you say that an experienced welder checked your welder.
Maybe you could ask him to give you an hour or 2 of his time if that’s possible to give you some instruction in how to set up the welder for the correct voltage and wirespeed for your particular application.
I‘ve been doing some practice on thin metal using this process and as I mentioned I’m a complete novice though I do have a new welder Paton Psi 200, and I have a feeling that it’s the welder that’s making my work look acceptable rather than my technique but after joining butt welds and grinding back the join is not visible, but that’s after hours of practice on scrap metal.
But whatever and it’s been mentioned earlier in your thread, don’t be practicing your welding on your pride and joy, you need to be proficient before you put a welder near your car.

 

[dave h 2]

Dave, you make some really good points here and some suggestions as to how I can get out of the mess that I have created. I know I need more practice but there is something different about the 1953 steel as I get a good sizzle noise from welding on the new steel and the moment I hit the old steel this turns to a phutt sound, some sparks and very quickly a hole. The old steel seems solid enough before I weld. Perhaps post war there was a higher carbon content in the old steel?

Some 60's -70's cars like HA Viva's, Datsun's and anything Italian are said to have rotted due to the inclusion of copper in the steel scrap added to the furnace. Panels still had to be bashed into shape so extra carbon may have made cracking when pressed more likely.

 

[eddie49]

When the original metal melts away as you try to weld to it, this indicates that it has been thinned by rust or by sanding. Either way, I would suggest cutting back further to reach really solid metal.
To make it easier to follow the weld line, I prefer to cut straight lines and square corners on patches. As a guide to mark the line on the car, I use a magnetic rubber strip taken from the door seal of an old fridge.
Another issue is that the edges of the hole should be cleaned on the rear side as well, otherwise rust, paint, or underseal will bleed into and weaken the weld pool. This can be done with a hooked scraper, or an "upside-down" sanding disc in a Dremel-type grinder.
Although it may seem illogical, a lot of people find that 0.8mm MIG wire is better than 0.6mm on thin sheet.

 

[MGnuts]

When the original metal melts away as you try to weld to it, this indicates that it has been thinned by rust or by sanding. Either way, I would suggest cutting back further to reach really solid metal.
To make it easier to follow the weld line, I prefer to cut straight lines and square corners on patches. As a guide to mark the line on the car, I use a magnetic rubber strip taken from the door seal of an old fridge.
Another issue is that the edges of the hole should be cleaned on the rear side as well, otherwise rust, paint, or underseal will bleed into and weaken the weld pool. This can be done with a hooked scraper, or an "upside-down" sanding disc in a Dremel-type grinder.
Although it may seem illogical, a lot of people find that 0.8mm MIG wire is better than 0.6mm on thin sheet.

Thanks Eddie, you have made some interesting comments and some good tips too.

 

[Barking Mat]

I often find I have difficulty seeing what I'm welding too.

I've found an led floodlight, behind me on a step ladder works a treat, don't hesitate to get extra light in there, really helps.