Mig tips drill & tap

[Whiskeymike]

For Tweco Mig tips, is the threaded portion 1/4 28 thread?  In looking at these things, I can’t confidently figure out if it’s 1/4 28 or M6 metric.

whats the proper drill and tap for these?

[jwmelvin]

It depends on the model of tip. I use the 11- or 11T- tips, which are M6. I believe the 14- or 14T- tips that Mikey has recommended are 1/4-28. For me the M6 was perfect to directly thread the brass tube I am using for an accelerator, which is also the right size to solder into a drilled 1/8 NPT plug.

[Mikey98118]

Most Tweco style MIG tips are 1/4-27 thread, which will work in 1/4-28 tapped holes, if you are careful when screwing them into place the first time the MIG tip is used. On the other hand,  in the last twenty years 1/4-27  taps have become almost as cheap and easy to find as standard 1/4-28 taps, so why not use the right tap these days?

[Frosty]

Some places carry SAE and others Metric, some both and all the major manufacturers cover both markets. It'll say on the package, if not ask the guy at the counter for the correct drill and tap. They have them on hand as the guns need the threads chased when they get damaged. 

This is another GOOD reason to go to a welding supply if at all possible, online isn't the place to get this kind of question answered or resolved. And NO the guys at a Big Box or even good hardware store aren't likely to know the right answer.

Frosty The Lucky.