The contact tip is a very important part of the torch and the welding process. Even slight changes in the tip including the ID, roundness, cleanness, etc., can have a significant impact on the quality and consistency of a weld.
Make sure you choose the correct contact tip for the wire you are using. A 1/16" contact tip should be used for 1/16" wire as its ID will be slightly larger than 1/16" to allow smooth passage of the wire. An ID too small will not let the wire pass through. An ID too large will cause erratic arc, allow the wire to wander, and wear the tip unevenly.
As wire runs through the contact tip, the tip will wear and its ID will change and the exit hole can become oval. Too much change will cause the tip to underperform and weld consistency to go down. D/F Machine Specialties contact tips are long lasting and will help you get from shift to shift to maintain convenient tip change intervals.
Spatter buildup can also affect the performance of the contact tip. Spatter that gets stuck near the end of the tip can essentially change the shape and size of the ID. This can cause similar problems to the ones previously stated. Always make sure you have a clean tip with its size and shape intact.
If the contact tip enteres the molten weld pool it should be replaced as it has now been contaminated. Weld metal can stick to the tip causing the tip to lose shape and conductivity.
Do not let the tip hang loose in the front of the torch, for this can cause unnecessary resistance heating. Threaded tips and collet nuts (for slip-in tips) should be threaded completely into the front end, tight enough so they do not move, but only hand-snug as to not damage the threads. Never tighten or loosen a D/F threaded tip or collet nut with anything but the D/F part #12111 wrench.