Not knowing your welding experience, the basics.
As you use the welder, the contact tip wears out making the hole bigger.
At some point, when the wear is too much, when you trigger the gun, the wire will burn off inside the contact tip.
Time for a new contact tip.
Pick up a bag of contact tips that match your welding wire size at your local welding supply store.
Do not cheap out and buy only one tip. For sure, on a sunday night you will need a new one.
If you have a gas-less wire, it is commonly called duel shield.
It has a flux core.
You said the 0.8mm wire went through the 0.6mm tip, but it would not feed.
Use only enough tension on the DRIVE rollers to feed the wire.
Too much pressure on the drive rollers will crush the wire and it will not fit through the contact tip.
At our shop we use CO-2 gas with the duel shield wire.
Hope this helps.
· 1 decade ago