just having a think. i am planning to properly replace some questionable repairs on my van over an extended period of time. the van will remain on the road and registered as it will be my only form of transport. i dont feel it is safe to use a mig when there is a petroltank in the car, and i dont want to have to pull the engine and petroltank 10 times (once for each repair) which leads me to wonder about gas-only welders, the sort that are basically a blowtorch where you hold the welding rod in your spare hand and super heat the metal. are these safe to use with the fuel tank in? are they exessively hard to use (i picked up mig-wel;ding very quickly)?

thanks

Hi bbck,
Oxy-acetylene welding is no safer (nor more dangerous) in terms of fuel fires than MIG or any other sort of welding. Each welding type is a potential source of ignition, one of the three elements for getting a fire going (fuel, oxygen, source of ignition) and oxy-acetylene is no exception, with the naked flame an excellent source of ignition.

You'll have to assess how risky it is, depending on proximity to fuel tank.

By the way, not what you asked but I find oxy-ac. welding is beyond the limits of my (limited) dexterity; it is not easy juggling flame temperature, metal temperature, flame distance, rod feed, speed and depth all manually. Since you are good with the MIG, you'll probably be much better than I at this. The advantage of oxy-acet.welding is that relative to MIG, it puts less heat into the panel, so less distrortion when done well and easier for post-work.

hth

Dude, are you talking about old fashioned oxy/acetylene welding? AKA a gaseaxe or blue tongue spanner??
If so it wouild be fair to say yes, they are quite a bit more fiddly to learn than MIG. This is particularly so when welding vertical surfaces.

Results are much usually the same but the torch will apply more heat over a larger area for longer than migging.
However, the nature of using fillerwire by hand as opposed to machine fed allows you to easily keep the weld bead level with the parent metal and therebygreatly reducing the amount of grinding needed later on.

I personally do nearly all of my welding with a blue tongued spanner save for bigger plate.

I agree with Tassupervee. Did my all 1302 rust repairs with oxy. New heater channels and many new panels.

Once you get proficient at it and prepare the replacement panels with almost an interference fit you almost do not need filler wire.

Brendan

I found it difficult at first, took me a lot of practice to be able to do half decent welds. It is a bit more dangerous as you have a naked flame going all the time (just means you have to be more careful) and it's not practical in tight spaces. I prefer doing panel work with an oxy, mainly because the weld metal stays soft and malleable like the metal around it - and makes it simple to panelbeat. whereas MIG welds tend to be brittle and crack when you beat them. Also I find I can usually make better welds with an Oxy, you have much more control over heat, filler etc. especially when you are doing really precise kind of work. Also it is infinitely more versatile as a tool for heating, cutting, brazing, also easier to setup for different metals than a MIG.

You can metal finish a fusion (oxy) weld, but you cant metal finish a MIG weld. That said, a MIG weld is stronger in some circumstances. The heat required to fusion weld is not allowable on any chassis repairs as it lowers the tensile strength of the metal. Of course that is not such an issue with panels that bolt on.