I am repairing an old Howard 350 rotavator. It's basically sound but the previous user/owner had allowed the tine bearings to completely disintegrate and one of the consqequences is that the chain drive has made some holes and cracks in the chaincase.
Now the chaincase is pretty sturdy, 16swg or maybe even thicker mild steel, say 1.5 or 2mm. Thus I have been able to weld the cracks successfully with my old ClarkeWeld arc welder using 1.6mm rods. In fact I've made quite a reasonable job of it! :-)
However the holes present more of a problem because the metal around them is quite thin as it's been ground away. Will a MIG welder make fixing these easier or will I need to fix patches in place somehow anyway? Can any sort of welder allow me to build up across gaps easily? The biggest holes are, say, 1/8" diameter, and I have some longish holes which are maybe 1/16" across and 1/2" or so long. What's the best way of dealing with these?
MIG should work fine for this. I've just patched a sump that was like a sieve on a Metro using a MIG welder.
You have to get bead of weld all the way round to start with. You may have to chase after it if its burning away or leave to cool a bit and go back again later. Then just weave back and forth filling the hole in the middle. You can grind down flat if your bothered about appearence and fill any holes again until your'e happy.
They are great little machines, you'll probably find yourself using the MIG in favour of your Arc welder. I've welded 1/4" plate with mine without any problmes and got much better results. You need a little practice to get the wire feed rate and gas settings right, when welding correctly you should hear a continuous hiss like frying bacon. If it's spitting you need a little more gas. You should have the wire feed set so that there is about 1/8" to 1/4" of wire sticking out as you weld. Too fast and the gun gets pushed away from the work piece. Too slow and you end up running out of wire and welding the end into the tip, you can get the wire out again with a bit of poking round but you sometimes have to sacrifice a tip if it's too bad. Keep a pair of wire cutters handy as you have to cut the wire back to size when you miss the workpiece, more so when patching holes and you're chasing a burnaway.
Don't go for the cheaper gasless only welders, they are no way near as good. You get lots of fumes and slag buildup as with arc welding so you have to do a bit of guesswork as to whether you've got it right. You can use the gasless wire in a gas mig if you're in a fix with no gas left, just make sure the welder can take 0.8mm wire.
The small disposable bottles don't last long, try to get a refillable one if you can. If not Machine Mart and probably others do a higher capacity disposable bottle which works out a bit cheaper, can't remember the size and my catalogue is at home! The CO2/Argon mix is best but C02 is OK and a bit cheaper.
I suppose so, I've never tried patching holes in thicker metal with an ordinary welder. Try with the lowest power setting first and work up if needed.
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